3rd gen fork setup

Greetings - New to VFR and forum. I recently acquired a 1991 VFR. One owner, but came via another party so do not have direct access to past history. Bike is not quite as nice as Treestylist,... 70K+ miles. Did come with extra set of wheels and front float rotors (from 4th gen?), as well as a box of misc. air filters, oil filters, manuals gave some hope it was owned by responsible person. Also has a FOX rear shock, so thinking owner did have right idea in mind. Was a great deal, but had to buy - no ride. Had anticipated a complete go through. Had not anticipated bent fork tubes.

I have now read through many past forums on suspension and looking for sage advise. 

I have new tubes on order with Frank's - 

Have all new bushing, seals, head bearings.

Made a stem nut adjust tool so if anyone local needs to borrow can do.

Have head reassembled but trying to find an ounce spring scale to adjust to the Honda spec of 1-1.5kg pull at leg.

In tear down have discovered that this has RaceTech 1kg/mm springs with a preload made from a thin wall electrical conduit,...not to thrilled with that part.

These may be on the stiff side as rider weigh in at 165, no luggage?

It has RT compression gold valve with a set up for their "C33" stack - NO bleed hole?

Not clear if the rebound piston is stock or RT? It has 10 17mm dia. x .01 mm shim stack. - NO bleed hole.

Can someone explain what the bleed hole does as it seems to me that the top of rebound piston has a (by-pass) valve that would allow oil to be forced to the top side that can not go though the compression stack and therefore "Bleed"oil to the top side?? What would have been the result of this being used without the bleed holes? IT must have worked to some degree? I only rode it for a very short distance when loose head bearing (result of whatever happened to forks?) came to light. I did notice it seemed to dive badly on braking.

Have called RT to see if they could provide original info from owners name,..They have name in record but no spec's. They are nice but answers are cryptic at best. They suggest that I order a complete new shim set at $60+ and with that get a new "code" to get set up for me. Not unreasonable but think that this set up could be close to correct. I just want to verify the rebound stack - my understanding is that if the rebound is still stock then may not be adequate for the stronger springs and be overpowered on rebound.  What the logic is of the bleed holes and should I add these to both compression and rebound?

How is it that no one seems to have put together a spreadsheet of RT data so we can do our own calculations? Would love to hear from 3rd gen owner who have RT set up and any clues  of what works and what does not.

Wow ! Long post with a lot of questions. 

5 hours ago, RhodeMoto

They suggest that I order a complete new shim set at $60+ and with that get a new "code" to get set up for me.

No need. Just go to the VFRD download section and find the instructions for the Gold Valves. Rebound and compression sheets are available. 

E.g. "Racetech Gold Valve Rebound instructions FRGV S02"

The only thing your $60 will buy you is RT's pick among their standard recipes (and a few extra shims which you probably won't need). 

6 hours ago, RhodeMoto

Not clear if the rebound piston is stock or RT?

If it's gold coloured, it's a Gold Valve. 

NB: RT used to recommend keeping the stock rebound pistons on the 3G VFR and simply modifying the shim stack.

6 hours ago, RhodeMoto

t has 10 17mm dia. x .01 mm shim stack.

Are you positive they are .10 mm?

If so, that's wrong. They should be .15 mm and that's a massive difference as the thicker shims are 3.4 times stiffer !

If they are in fact .15, that's very stiff already. See the RT instructions sheet. 

8 hours ago, RhodeMoto

In tear down have discovered that this has RaceTech 1kg/mm springs with a preload made from a thin wall electrical conduit,...not to thrilled with that part.

These may be on the stiff side as rider weigh in at 165, no luggage?

1 kg/mm springs seem about right for a stock 3rd gen with a rider your weight, that's the spring rate I use in my 4th gen and I'm the same weight as you. The thin walled tube is likely the stuff RT supply with their springs, don't worry it's 6061 T6 al. and totally up to the task.

Quote

Can someone explain what the bleed hole does as it seems to me that the top of rebound piston has a (by-pass) valve that would allow oil to be forced to the top side that can not go though the compression stack and therefore "Bleed"oil to the top side?? What would have been the result of this being used without the bleed holes? IT must have worked to some degree? I only rode it for a very short distance when loose head bearing (result of whatever happened to forks?) came to light. I did notice it seemed to dive badly on braking.

Some forks use a tapered needle which screws in and out of an orifice to adjust low-speed damping by metering (bleeding) oil flow past the shim stack. Sometimes this is for rebound only, more modern cartridge forks have separate adjusters for both low speed compression and rebound damping. When installing RT (or Ohlins FPK etc) pistons in cartridges without a low speed adjuster it is necessary to drill a bleed hole to emulate the effect of a partially open adjuster needle, the size of the bleed hole directly effecting the rate of flow. I believe the gen 3 forks are adjustable for preload only, if replacing the stock pistons with RT units I would expect both the compression and rebound pistons would require bleed holes to be drilled BUT consult RT or a suspension shop in your area - I have not opened a pair of 3rd gen forks myself. 

I suspect the bypass you noted on the rebound piston is the check plate which opens on the compression stroke to allow oil past the rebound piston and closes on the rebound stroke to force oil thru it. 

Quote

Would love to hear from 3rd gen owner who have RT set up and any clues  of what works and what does not.

I think having a thread that served as a suspension data base would be a great idea. 

You can check the spring rate RT recommend on their website. No need for a valving code. 

I had a look out of curiosity and 1.0 kg/mm is spot on for a street rider on a 90-91. 92-93 require 0.9. Not sure why. Lighter bike apparently. 

Do verify the weight that RT has in its system for your bike. what they show for the VF500F is way off.

I also phoned them and asked what the mean by "semi-wet"....  they could not tell me....

12 hours ago, RhodeMoto

NO bleed hole?

That's nigh impossible.  :huh:

If the pistons were not drillled there must be a bleed somewhere else otherwise your forks should be incredibly stiff, especially on the brakes.

RT's instructions / kits are pretty generic and won't tell you exactly what to do for your specific model. Your kit fits pretty much all Showa forks with a 20 mm cartridge (Ducati, Aprilia..) 

For example, my 6G uses the same kit and has no bleed holes through the comp pistons because there is already a bleed elsewhere. 

Look really closely before drilling !

It's just weird that you experience a lot of brake dive since the spring rate is correct. :blink:

The only explanations I can think of are:

1. There is a bleed elsewhere and it is much too large. 

2. Your fork oil is abnormally light

3. Your fork oil is all but gone and the cartridge is pumping air.

Or any combination of the above. 

I agree with the points that RC36 is making. Compression bleeds (and RT would recommend something like 1.3mm diameter) will be either through the wall of the compression valve to bypass the shim stack, through the centre of the bolt that holds the assembly together (and that is most likely what the rebound valve will have, and what the 6th gen compression valve has) or if someone has been fiddling, I have also heard of a bleed being drilled through the wall of the cartridge tube, usually down low just above where the compression valve sits. The stock set-up for the 5th gen uses a smaller diameter thin washer below the main shim stack that keeps those shims just clear of the sealing face of the valve body, and yet another set-up (in my ST1100 for example) has the bleeds as small machined-out channels in the sealing face of the valve. 

If there is excessive dive then you may have an over-sized bleed somewhere as above, not enough oil, or maybe the o-ring that seals the compression valve to the cartridge tube is leaking.

I would not worry about the use of PVC tube as a spring spacer; that will work fine.

As baseline settings for shim stacks, the C33 (has 3 x 0.15mm x 17mm main shims) is a good standard set-up, and on the rebound side you'd be wanting something like 6 x 0.15mm x 17mm shims; as RC says a 0.15mm shim is 3.4 times stiffer than a 0.1mm, so having 10 x 0.1mm shims sounds a bit light to me, especially with the 1.0kg/mm springs.

31 minutes ago, Terry

maybe the o-ring that seals the compression valve to the cartridge tube is leaking.

Good point.  :idea3:

Could be that the lack of bleed hole was deliberate as a way to counter seepage past the seals. If so, this needs fixing. 

Great overview of the different ways the low speed circuit can be implemented as well.  :fing02:

The compression pressure is generated mainly by the entry of the damper shaft into the cartridge, which forces incompressible fluid to leave the cartridge, ideally through the bleed and compression shims. In reality, there will also be a little leakage back up the damper shaft seal at the top of the cartridge as well. The rebound valve also plays some part in compression damping as there is three times as much fluid passing through it, and any change in restriction (e.g. changing an adjustable rebound bleed) has a notable effect on compression as well.

I've just fitted CBR600F4 forks with adjustable compression bleeds (fluid passes through a hollow bolt, exits under the valve body and passes though an adjustable needle valve back to the outside of the cartridge) and playing with this is changing my understanding of the ride effect of the compression bleed. 

5 hours ago, Dutchy

Do verify the weight that RT has in its system for your bike. what they show for the VF500F is way off.

Why, oh why don't you listen to me Dutchy ?  :goofy:

I think RT use the sprung weight which is a bit confusing as it doesn't match the overall bike weight but it is the correct weight to use. 

Having said that, I obviously cannot vouch for the accuracy of any of RT's figures. 

I can OTH categorically say that the stock fork spring rate they quote for the 6G is wrong since I rated them myself and there is no way they are .85 kg/mm. At best, it could be an average rate over the whole stroke. 

Whew - Great input.

• NB: RT used to recommend keeping the stock rebound pistons on the 3G VFR and simply modifying the shim stack.
  • This seems it may be the case here, and the first time I have heard reference to this. I was thinking the rebound and compression would have been a set from RT.
  • This is the rebound set up. The shims are 0.1mm x 17mm dia. - 10 
  • The piston looks like what I have seen in photos of SHOWA. NO bleed hole. There are very small notches in every lip as if to allow minimal passage? Next photo
  • Anyone have record of what stock shim valves were and is this greater? It does seem that this should be increased at least 25% (over stock) to match the spring rate,and that just to match original rebound rate.
  • To Terry's point  - This may be too light and may be straight stock - Odd that someone would go to all the trouble of doing this and not get it right. NO bleed holes, not changing the rebound,...
  • While on the rebound piston topic,... If the check valve can open on the compression stroke, is that not acting as just as a bleed hole to meter oil at low velocity? Why do you need additional hole?
  • [image: Displaying 20161101_180956.jpg]

                     [image: rebound piston.jpg]

• This is the compression setup as removed.
• [image: compression stack.jpg]
  • This seems to match the RT - C33 stack.
  • The valve is GOLD and appears to be RT.
  • NO bleed hole - there is no other path to pass the shim stack,..
  • O-ring seals are good but will replace for good measure.
• To Terry's points
  • I measured oil and was close to spec, no idea on weight but seems thin but I am used to running old school stuff with 15wt.
  • That pre-load spacer just bothers me to have so thin a wall - PVC seems a better choice. I have been toying with the idea of running a short lighter weigh spring as a two stage so small road bumps are absorbed but will bind out quickly so not affect dive?? Would have to turn a stub spring connector and then re-calculate the pre-load,... (OK leave that out -have enough to worry about)
  • So - still wondering about the dive factor and cause? Is it possible that the top side of rebound piston - check valve is allowing too much flow?
• The cartridge is drilled only below the compression o-ring so no additional bleed through that tube.
• I like the idea of spacing the compression stack from the face as then bleed can be adjusted.

So in conclusion  - Wish I had junked this front end and swapped for a fully adjustable fork setup,.....

NO - I am determined to get this sorted.

Assuming:

- The spring is right

- The compression stack is right

- The rebound stack flex should be increased.

- Both compression and rebound should most likely be drilled.

Thanks for all the input.

Firstly you have a standard looking rebound valve; I doubt very much that the shim stack is standard, they normally would only have 3 17mm shims, not 10. 10 x 0.1 mm shims is IMO a bit light, but not stupidly so. The notches in the shim sealing face are the rebound bleeds. Don't add any more bleeds to the rebound. The notches allow fluid to pass through the check valve ports when the check valve is closed (rebounding); so some fluid will pass through the bleeds until the flow gets high, then the shim stack comes into play.

I agree that the compression valve is a Gold Valve with C33 stack. Very odd that there is no bleed drilled in the valve body then; someone didn't read the instructions methinks. Do double check for the presence of a 1.3mm hole in the gold valve casting. In the absence of either drilled bleeds or a bypass notch, my 5th gen had a 12mm x 0.1mm shim between the OEM valve body and the shim stack.

7 hours ago, Terry

agree that the compression valve is a Gold Valve with C33 stack.

Not quite C33 as there is a .19 shim in there. Measurement error ?

The third shim also looks a bit suspect to me. Looks like it is not quite flat judging from the reflection of the light. 

I just cannot believe that you have no low speed bleed, no seepage, 1.0 springs, normal oil height AND still experience excessive brake dive.  :wacko:

Edit: Or maybe I just misread the .19.  :ohmy:   :blush:   :laugh:

7 hours ago, RhodeMoto

There are very small notches in every lip as if to allow minimal passage?

These notches are your low speed bleed. Remember, it only takes a single 1 to 1.3 mm round hole so the required passage is indeed minimal. 

As Terry explained, the volume of oil that needs to go through the compression valve corresponds to the volume of the damping rod entering the cartridge minus a bit of seepage (as little as possible but surely never zero). 

8 hours ago, RhodeMoto

While on the rebound piston topic,... If the check valve can open on the compression stroke, is that not acting as just as a bleed hole to meter oil at low velocity?

Oil needs to pass through the rebound valve as it dives into the cartridge but the volume of the chamber above the valve is reduced by the volume of the damping rod entering so an equal volume of oil needs to exit the cartridge in order for the forks to compress at all. 

BTW, if you look closely, you can see that the check valve plate is designed to just lift off (not bend) the piston face under the slightest pressure and that the ports it obstructs are about as large as they can be. 

RhodeMoto, 02/11/2016 at 3:38 AM

I measured oil and was close to spec, no idea on weight but seems thin but I am used to running old school stuff with 15wt.

RT's standard is very much on the light side of 5W so that seems normal. 

[image: sketch-1479221907681.png]

8 hours ago, RhodeMoto

Is it possible that the top side of rebound piston - check valve is allowing too much flow?

Nope ! (err... I think :unsure: ) 

Firstly you have a standard looking rebound valve; I doubt very much that the shim stack is standard, they normally would only have 3 17mm shims, not 10. 10 x 0.1 mm shims is IMO a bit light, but not stupidly so. The notches in the shim sealing face are the rebound bleeds. Don't add any more bleeds to the rebound. 

Those are 10 shims at 17mm dia. and all 0.1 thick. If 3 are stock then this should be quite a bit stronger rebound,... Would a tapered stack respond better as this is going to be be full on at rebound. A tapered stack would open early with softer rebound and increase with velocity? Yes?

Not quite C33 as there is a .19 shim in there. Measurement error ?

That may be my writing on the check valve measure at 0.4mm -on the rebound. The compression is 3 @ 17mm x  0.15 (second from left is scribbled over). Will have to check caliper as the others I had at 0.11 and most likely 0.10.

Has anyone checked out this software? Looks like it could be a great tool, and not much more than RT wants for a shim stack,...

www.shimrestackor.com  

Where can you get shims other than RT?

1 hour ago, RhodeMoto

Has anyone checked out this software? Looks like it could be a great tool, and not much more than RT wants for a shim stack,...

www.shimrestackor.com  

I haven't bought the software but I've read all their free material. 

I'd buy it in a heartbeat if I was a competitive MX rider but for a road bike it seems overkill. 

So - if 21 members want to send me $4 I will get this and run their specifications,......

8 hours ago, RhodeMoto

Will have to check caliper as the others I had at 0.11 and most likely 0.10.

I wouldn't sweat it. Shims are available in 0.05 mm increments AFAIK so they are likely indeed 0.10. Calipers are not precise enough for accurately measuring to 0.01 mm but plenty good enough for 0.05.

Incidentally that makes my remark about the 0.19 shim a bit silly.  :laugh:

Could be a 0.20 though but RT's kit does not contain any. Only 10's and 15's.

The OEM stack (for my 5th gen) included 8 x 0.2mm clamping shims on both rebound and compression, just under the 11.4 x 0.4mm spacer.

Tapered stacks seem to be recommended by the aftermarket on the compression stack, but the rebound stacks that I've seen do not use the same set-up, just a small diameter (9mm) clamping shim and the 17mm main shims.

AFAIK, the compression stack has to deal with a wide variety of speeds and forces, whereas the rebound stack is just dealing with the same spring rebound force each time. 

I am getting a better understanding of all this,... thanks again for input.

The logic of terry's explanation on rebound shims makes total sense. 

No reason to have tapered stack if we agree that rebound is a fixed rate and not dealing with variable rates of input as compression.

However RT does list their rH stacks as tapered sets?

Forks by Frank have been shipped - due in Nov 8. Have heard mixed feedback on these, but decided to give them a try. 

Want to finalize all this valving so I can be onto assembly as soon as they arrive.

Called RT again today - Each time I get a few more crumbs,...

Early versions only had the compression valve. The rebound was not offered.

They have NO record of early instructions and can not verify or suggest a rebound stack.

But assume that there was some re-set additional shims.

I can buy a pair of rebound valves at $169 complete with extra shims, free locktite, and a secret code!

Sort of confirmed that the 1kg spring & C33 compression would be appropriate.

The bleed hole must be drilled (compression)- puzzling that this would have been ignored.

Confirmed 5wt oil, at 120mm air gap

OK - If the original rebound shims were 3 @ 0.15 - and they are 3.4 times stiffer than 0.10 shims, then that would equal 10.2 shims @ 0.10.

This change would be pointless as I am now (10@ 0.10) equal to stock,....IF the spring is now 25-30% stiffer - then the rebound valving (assuming stock rebound was spot on) should be same increase. Suggestion (Terry) above is 6 @ 0.15 as base, that is 2X stock? Maybe too strong /slow rebound? RT is even greater if you use the 4th setup (relative to the c33 settings?). They use 6 @ 0.15 + 3 more @ 0.10.

My gut feeling is that I would prefer to be on fairly stiff springs with a quick/stiff compression, and have the rebound act relatively fast. 

I do not have any shims on hand so unless anyone feels strongly that this rebound is way too soft I am going to;

Drill the compression bleed hole

Cut some new pre-load spacers.

Use the shim stacks just the way they are

Re-assemble the whole mess - all new bushings and seals

Ride this thing and see what I have.

The original rebound shims would have been 3 of the 0.1mm thickness, not 0.15. I've not come across any 0.15mm thick shims in Honda forks yet (and I onto my 4th different model now). 

I agree with your plan above. Now that you know exactly what you have in the fork, it is time to go riding and be as analytical as possible.

Here are some links to Gold Valve instructions that I've received with parts purchased over the years. The compression instruction is the old version which gives specific advice on revalving a stock rebound valve.

https://www.dropbox.com/s/cuen74nrsz3dck6/Racetech Rebound Gold Valve Instructions.pdf?dl=0

https://www.dropbox.com/s/c3t3c8ygt00dnxx/Gold valve compression installation.pdf?dl=0

I'll see if I can find my "early" RaceTech Gold Valve installation instructions, but it also sounds like you've got this sorted (thanks to excellent advice from Terry and RC36Rider).  I once wrote up a web page on an NC30 Gold Valve install (which I found amusing to read again more than ten years later!)  In it, I reference the fact that the FMGVS2040 kit instructions call for the drilling of a 1.3mm bleed hole (and lament that RT hadn't done it already).

Ciao,

Another thought about your brake dive:

Check your sag / preload. If the bike has been pitched forward significantly (frequent change on VFR's) this can have a fairly pronounced effect on the rate of dive. 

I know because being a sloppy lazy guy, I didn't bother cutting new preload spacers when I changed my fork springs and ended up with the front riding too high (very little brake dive).

I subsequently cut new spacers 10 mm shorter and was amazed at how much softer the front felt.

I emphasise "felt" because preload does not affect spring stiffness or damping in any way but it still feels like it when grabbing a handful of front brake 

Just a thought. 

And yet another thought...  :laugh:

Having no low speed bleed should (if my thinking is correct :unsure: ) lead to a sort of "crunch" effect where the forks won't budge at all until a certain threshold of force is reached, then suddenly resume normal behaviour. 

This could be experienced as pronounced brake dive as the forks would then tend to "catch up". 

It could also conspire with your bent forks (depending on how badly and where they are bent).

In short, the effect would be similar to having a very high amount of stiction. No good.  :excl:

Whether the above is more or less correct or not, I think the best course of action is indeed to fix what is obviously wrong (i.e. drill a bleed and replace fork tubes) and only then start worrying about your shim stacks.

[image: 772148-tr-race-tech-rebound-gold-valve-f]

Another tidbit about rebound valves. 

The above are RT's classic rebound GV's. The (relatively) small round holes are the rebound ports while the large kidney shaped ones are the refill ports (check valve side).

I think it's obvious that they designed the refill ports for max flow.

To the extent that the rebound valves have an influence on the compression stroke, I tend to think that it is not really intended, just not always avoidable. 

BTW, if you compare the port geometry of your stock Showa rebound pistons with the GV, you'll see that the rebound ports are larger and the refill ports correspondingly smaller. 

That's bound to have an impact on your shim stack. 

The consequence IMO is that the Showas require a stiffer stack to achieve the same rebound damping force and that they are more likely to become restrictive on the compression stroke (but the latter may be of no practical consequence. Dunno.) 

Also,  check very carefully that the check valve plate is as free to move as it can be. 

4 hours ago, JZH

I reference the fact that the FMGVS2040 kit instructions call for the drilling of a 1.3mm bleed hole (and lament that RT hadn't done it already).

They let you choose between 1.0 (racing) and 1.3 (road). Also, some bikes do not need the hole at all (e.g. 6G VFR). 

I understand that RT will drill for you if you ask and specify what you need. 

For better or for worse, RT's kits are not specific model dedicated drop-in kits.

IIRC, I bought my FMGV S2040 from an Aprilia dedicated website where it was listed for the RS250. Clearance price.  :biggrin:

The compression valves supplied by DMR for my 4th gen (same forks as later 3rd gens) do have a 1mm bleed valve

[image: PB041270.jpg]

[image: PB041273.jpg]

Never got to install them on my redslut..... 

You see? Now I HAVE to buy an SP2 for them! :goofy:

44 minutes ago, Dutchy

Now I HAVE to buy an SP2 for them! :goofy:

Yes, you must !  :laugh:

And I'll ride to Utrecht with a bottle of Champagne if you let me have a go.  :goofy:

Joking of course. I know you prefer a good single malt.  :beer:

I second the thoughts on a good single malt. If this all goes well I will have to pick up a bottle. Islay please,.....The cupboard is bare.

So  - Great to get the RT original instructions. 

Terry - are those your notes on stack in sidebar? The RT recommended seems a giant leap from stock, but written notes are even greater. How did this work out?

What I have and what is indicated here just seems like a huge jump from stock, if stock is 3 @.10.

I am basing this all on the thinking that the spring rate is 25-30% greater and therefore the rebound should go up proportionately.

Do I use all 10? Drop a few?

Heading out to pick up a #55 drill bit.

Islay.....  Can't go wrong there eh? :-)

[image: IMAG5799.jpg]

Back to shims again.... 

Wow - Similar tastes. Have had all but the two on right. The Ardbeg Ugeandal (sp?) is possibly my all time favorite,...

So took my FZ650 for an afternoon fall run to the hardware store for the #55 bit. They were closing and some very well meaning young guy grabbed a bit out of drawer and handed it over. I should have been more alert as when I got home discovered it was way to big. Trip two to a different store and have it in hand. 

Used some #600 wet / dry on one rod and then polished it on buffing wheel. Get things cleaned up and the holes drilled. assemble what I can so when tubes arrive on Tuesday will be able to  button up and see what we have. 

Still perplexed as to using the entire rebound stack,......I keep was thinking that if the stock rebound was OK (3 x 17/0.10) and the spring rate is increased 30% then to maintain same rebound you should add one shim. Tonight's thought  (no scotch) is that spring rate under compression is not relevant to rebound rate. Is it possible that an increase of 30% compression equates to an exponential increase in rebound? So it may be a 60% increase in rebound that I now have to control. That gets me closer to what is suggested by RT instructions. Again - current stack is 10 x 0.10 or three times greater than stock.

I feel like this must have been owned by someone who had the right intentions, as there is a FOX rear shock with remote air, as well as these fork mods. But if the bleed hole was not done what else may have been done wrong or incomplete,....? Probably should check the torque on rear wheel before I go too far!

There is much to go over before I feel this will be road safe for extended tripping. Next on list is checking the temp gauge. In the short run I did have on this the needle did not move. I read that if you ground the lead to the sending unit and the gauge jumps then gauge is good and most likely the sending unit. Anyone with clues on this?

The hand written note was actually for my Suzuki RF900; but I took a punt and followed RT's instructions for re-shimming the OEM rebound (identical to the VFR's Showa valves) and it was great. As RC has inferred above, the same 20mm cartridges get used in a lot of different forks, so you can easily mix and match parts so long as you pay attention to things like fork diameter when choosing springs, and identify where the low speed bleeds are.

I also dropped the compression back to C32 in that RF900, and have done the same on my VTR1000, VFR800 and ST1100, as that suits the rough roads that I play on. C33 transmitted too many jolts to my ageing wrists. I also run lighter springs than you, 0.85 in the VTR, 0.9 in the VFR and 0.9 in the ST1100 (which being heavy should use 1.1 which I also have, but the 0.9s are much better for me). With hindsight, there's not much wrong with those 6-port Showa valves, they flow plenty of oil unlike the HMAS valves in the VFR and VTR which have tiny (relatively) ports, and I doubt there is much benefit from replacing them with RT valves.

I looked up some specs for the VFR750FV, and that should have had 2 x 17 x 0.15 and 1 x 17 x 0.1 shims on rebounds as standard. 10 x 17 x 0.1 shims is standard for a NC30.

Once again many thanks - Now feel I have enough information compiled to know I am not going blindly into this. 

based on this last info feel the rebound, if not perfect, will be a reasonable start point.

If I use a bend factor of 1 for a 0.1 shim then a 0.15 = 3.4

stock -                       (2 x 3.4)+1 = 7.8

increase spring rate -   7.8 + 25% = 9.75

my current set -              10 x 0.1 = 10

Drill the bleed hole and assemble!

Drink scotch!

Will report back with results.

2 hours ago, RhodeMoto

Drink scotch!

To quote the RT instructions: 

"Do not take this step lightly."

  :goofy:   :beer:

RhodeMoto, 02/11/2016 at 3:44 PM

Would a tapered stack respond better as this is going to be be full on at rebound. A tapered stack would open early with softer rebound and increase with velocity? Yes?

According to Shim ReStackor, there is no real difference between a tapered stack and a straight stack in terms of the damping curve they generate.

The main difference is that the tapered stack is kinder to the spring material as it spreads the bending forces more evenly.

The compression shims flex a lot (very wide spread of velocities) while rebound is much more limited hence a simpler straight stack is deemed good enough. 

At least that's what I think the rationale is.

Stack styles

This reinforces my move to go with basically what I have. The compression stack will hopefully be right on, now that I have drilled the bleed hole. I have faith the rebound will be close. 

Everything clean, assembled, and waiting on new tubes,.... 2 days?

Found a length of acrylic tube I had is a perfect fit to make some new pre-load spacers and trash the electrical conduit with cuts that were not square.

Any thoughts on discussions I have seen regarding "special" racetech  5 wt. fork oil? Is this a differnet viscosity than other 5 wt. ?

I had always thought that oil weight was the visitcosity, and 5 wt. was the same across the board.

Also - RT recommended 120mm fill height. That is more than spec. 

Anybody have opinion, experience weight, volume using RT mod's?

You are basically correct, 5W should be a standard, in practice what should be specified is a viscosity at 40C; 5W should be around 16-18 cP, and would be what I'd suggest.

Yes run with RT's oil level suggestions. To be clear make sure you have pumped the fork leg a few times to dispel any air, then do the same with the cartridge. It is very obvious to feel when all the air is gone and the damping is smooth over the full stroke. Once at that point, compress the leg fully and set the oil level, before the springs etc are added.

7 hours ago, RhodeMoto

Any thoughts on discussions I have seen regarding "special" racetech  5 wt. fork oil? Is this a differnet viscosity than other 5 wt. ?

Sort of. If you pick another brand's 5W, it is likely to be heavier than RT's.

As Terry says, go by cSt@40°C if you can find the info. Much more precise than the SAE system of "weight" which was never intended for suspension fluids.

The 5W I currently use is on the heavy side at 25.6 cSt@40°C whereas RT's is on the light side at 15-16. That difference can definitely be felt.  

At a minimum, you want to pick a brand and stick with it otherwise you'll be chasing your tail. Also check your tyre pressures religiously while testing. 

Quote

Also - RT recommended 120mm fill height. That is more than spec. 

RT use 120 mm for pretty much every road bike. Not really an issue as it is a safe starting point but they certainly over-hype how "personal" their set-ups are.  :pinocchio:

I'd think it's rather on the high side considering that the 3G has 140 mm of travel and not the typical 120 (just a rough rule of thumb this).

NB: The RT springs are almost certainly much smaller in volume than the OEM so that's a good reason to raise the oil height a bit. 

I'd probably start about halfway between RT's and Honda's recommendations but it's fairly easy to adjust so no big deal really. 

Yeah, it takes a little digging, but one can find cst info online

i.e.

http://www.putoline.com/en/search/#!/query:hpx/

http://www.putoline.com/en/catalogue/product/370/hpx-r-15w/1734/

Case in point: Putoline 4W at 16.90 cSt@40°C is actually slightly heavier than RT's 5W.

IMO, it does not matter hugely whether your choice of fork oil is a rather light or rather heavy 5W. 

My own choice is entirely based on local availability. It does not bother me as long as I know exactly what I have in my forks.

Or pick from one of these,....

http://mahonkin.com/~milktree/motorcycle/fork-oil.html

http://bmwmotorcycletech.info/ShockOilComparo.pdf

then got lost somewhere is this

http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid  

I am going to see if anyone local carries RED LINE. 

New tubes arrived today! Look very well made. 

[image: 20161108_125058.jpg]

Just found some potentially interesting info on...err... another VFR dedicated board: Stock shim stacks 

Seems that your rebound stack is actually stock.

2 hours ago, RhodeMoto

I am going to see if anyone local carries RED LINE. 

Peter Verdone uses Red Line for shocks, IIRC.

It has very high VI (temp stability of viscosity) which I'm pretty sure means $$$ for no real benefit as forks do not run anywhere near as hot as monoshocks.

- According to my (rough) estimates for my 6G, sprung weight up front is about 75-80 kg and the rider in normal riding position puts no more than a third of his bodyweight on the front wheel. 

I arrived at this by calculation based on my sag values, the known spring rate and the known preload. It's 100% guaranteed inaccurate (sag measurements taken alone are not very accurate) but it should not be waaay off either and better than nothing even for a 3G.

- You have a tapered stack in there where you counted the smaller OD .10 shims as 1, hence my remark. OTOH, I have no clue how much they contribute to overall stiffness so 1 might be better than nothing after all.

- Yes. Even if ShimRestackor works as advertised, it won't tell you what will work exactly as you'd wish.

Honestly, I'd just put in the RT rebound stack and see how that goes. You just might like it enough to forego any further fiddling. 

Nobody likes to mess with fork internals. I need to do my rebound stacks and find myself procrastinating big time.  :laugh:

Clearly one can get lost for far to long in this,.....

I did make the acquaintance of the head mechanic at the best and oldest dealer in Rhode Island. 

Left with a handful of shims! Just "return what you don't use".

Should be able to create the RT stack.

Do have to take the cartridge part again, but better than a complete tear down.

They were closing so did not a chance to see what they carried for oil.

Getting closer.

18 minutes ago, RhodeMoto

Getting closer.

:fing02:

Good deal on the shims. It's not that they cost so much per piece but I haven't found yet any place that sells useful assortments rather than packs of 10 (or 50) of one size.  :491:

Yes! This was a crude late night mess with own head endeavor. 

I was using rider weight as an indicator of or hopefully relative to sprung rate. Assuming anyone messing with shims had to be changing springs as well. 

Just put in what I had found to see if there was some correlation.

This is all regarding rebound so, as discussed earlier, shim diameter is mostly accepted as same for entire stack.

I really do not want to take cartridge apart that is all set for my shiny new tubes, but now that we have discovered rebound is at stock I feel adjustment should be made.

Even if I had shimstackor software, I would still be flying blind without a goal graph to shoot for. 

May be off here as well, but the range from plush to track could be charted, and should have similar characteristics with rider weight, etc. accounted for.

So if someone had software, and time on their hands, they could compile a reverse engineered average of all who have found their way the hard way,...

Then,......I could send my rider data and request a result that was say midway between track and plush, and get results.

[image: 20161113_091518.jpg]

Very nice chart. 

I'm using the stock .70kg springs. Wish somebody made a strait rate .75 for us lightweights.

You can also affect the 'hardness' or 'softness' of the stack based on the diameter of the clamp shim. (one of the things I'll try in the future-I only change one-at most two things a a time-to easy to get lost) Gives the shims a bit more room to flex, which is probably more of a consideration for the street than track. 

54 minutes ago, rangemaster

I'm using the stock .70kg springs. Wish somebody made a strait rate .75 for us lightweights.

Are you sure you want to stick with springs that light ?

The RT calculator has your 135 lbs at 0.868 kg/mm. 

Considering that the bike on its own puts upwards of 150 lbs on the front springs and that the rider puts about 33% of his own weight on the front, we get:

150 + (135 / 3) = 195 lbs

150 + (210 / 3) = 220 lbs 

=> Spring rate difference: 220 / 195 = 13 %

I'm pretty sure that you can use 0.80 or 0.85 with no problem at all. 

I am just making this up as I go,... I made up a reduction factor for the flex of the smaller dia. shims. Know this has no basis on reality, but thought it would still give some visual as to how different shims add up. I also have to work with what shims I have gathered. Will have to check the shim clamp dia. that I have - it seems most are 8mm? 

My proposed version is virtually matching R/T - Rh17, but with a tapered set. I know the discussion was that it did not matter for rebound,but,... I was reading the RT "bible" (mistake?) and there is reference to shim fatigue with all same dia.? The other thing mentioned is that there is some increase in oil pressure as the rebound stroke gets longer. R/T old school seems to have gone with same dia. - the "new" rebound list is all tapered.

My thinking is the 17mm stack will react first so if I zero the smaller ones out of the equation I get a force/lb factor of .123 (just about where rangemaster is). So starts compliant, then builds as each larger shim comes into play until it reaches full at .130/lb near Rh17 value.

So - time to sh_ _ or get off the pot.

Going to the basement and get to work!

Hopefully my next post will be with results.

Good on you Rhode. Let us know how you get on. 

I should warn you if I did not before...tinkering with suspension is also a recipe for disappointment. There is always the feeling that "it could be better if I just...". When you leave it stock, you can just say "well, that is how it is". Having said that, all three of my current bikes have "benefited" from my suspension tinkering!

Keep notes, and try to keep any testing as consistent/comparable as you can. I've tended to start with the RT recommended set-up of springs and shims, and then vary one element at a time (if my patience was up to it). I've spent the most time on my VFR and specifically on the compression stack, as I seem to have a bit of a deaf ear when it comes to monitoring rebound changes. I guess I sense the effects of the leading edge of bumps and dips, but care less about a few weaves afterwards.

YMMV

4 hours ago, RC36Rider

Are you sure you want to stick with springs that light ?

The RT calculator has your 135 lbs at 0.868 kg/mm. 

Considering that the bike on its own puts upwards of 150 lbs on the front springs and that the rider puts about 33% of his own weight on the front, we get:

150 + (135 / 3) = 195 lbs

150 + (210 / 3) = 220 lbs 

=> Spring rate difference: 220 / 195 = 13 %

I'm pretty sure that you can use 0.80 or 0.85 with no problem at all. 

A LOT of the stuff I've read says the Race Tech stuff is exactly that-geared for the track, so a bit stiff for a given weight for the street. That being said, I'm also dealing with New Mexico roads, NOT the most bike friendly I've been on. I'm more a sport TOURER than a SPORT tourer, being a old guy and all. But should I find a deal on some .80's, I would love to try your suggestion. With what stuff I've done it's still a bit harsh on the little stuff, but about perfect (for me) on the bigger stuff. 

2 hours ago, rangemaster

A LOT of the stuff I've read says the Race Tech stuff is exactly that-geared for the track,

RT's setups do have that reputation but what is frequently not appreciated IMO is that the spring rate does not have such a dramatic effect on suspension hardness over bumpy stuff.

I messed up a bit in my post above. I forgot to say that the 210 lbs rider is me and that I ran 0.90 RT springs in my 4G (way back in 2003). RT recommenced 1.0 but I was like you and let myself be convinced that it would be race hard so went with 0.90.

Result: Heavier springs (within reason) make the ride tauter but not harsh.

Harshness is mostly a function of damping, I believe. For the VFR (and most Japanese bikes), the road to firm and controlled yet plush is heavier springs, mild compression damping and adequate rebound.

Long story short, I think you can try 0.80 without any fear of turning the forks into a bone shaking, teeth rattling affair.

As a starting point, just make sure you have your preload / sag right and don't even touch your current valving.

Oh, and get your springs from DMr or some other place that sells Sonic's. RT is overpriced. 

I bought direct from Sonic, very easy and quick.


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One more thing. 

I'd wager New Mexico roads have nothing on Belgian roads when it comes to crappy tarmac. 

Pretty much anything that's a bit fun to ride comes at the price of a grotty surface over here so I am certainly not looking for a setup that is only fit for smooth stuff. 

New delema,..

All clean, shims sorted, ready to assemble.

The new tubes have a wall thickness of 3mm. This leaves an ID of 35mm. The OEM is 2.5 wall, ID 36mm.

The race tech Springs are 35mm.

I can push the spring in, but it is not a drop fit. Seems this would bind and or wear the inside of tube.

Ideas?

Does anyone need some 1kg springs? I could probibly drop to .9 or .95 if someone wants to swap. Need spring to be 34mm dia.

6 hours ago, RhodeMoto

The new tubes have a wall thickness of 3mm. This leaves an ID of 35mm. The OEM is 2.5 wall, ID 36mm

Oh, bummer !  :huh:

I use the 35 mm OD RT springs in my 6G's 43 mm forks with no problems but I would not use a spring that is a tight fit.

All coil springs need some clearance as they widen a bit under compression.

Fork springs being long and slender also have a tendency to buckle so they need that little bit extra. 

No way around getting new springs there, I'm afraid.  :unsure:

Once bought, them springs do not eat any bread, so store them..

New ones do cost bread...

c'est la vie....

20 hours ago, RhodeMoto

Does anyone need some 1kg springs?

I could use them but I checked the shipping rates to Europe and that would only leave you with some pocket change for your trouble.  :huh:  

If you can't return the Racetech springs for a more suitable size, I'd suggest you go to Sonic Springs as they manufacture and supply to others, so I suspect they will be able to provide exactly what you need.

Story form Sonic;

Ours are 35mm (nominal) also, actual is in the 34.8-34.9 range. There is a
bit of variance. You do need a little room, but you don't need much. I'd
try them and see, if they just drop in you're fine, if there's any
interference or binding at all then you need smaller OD springs. The next
size down that I have is a 32mm OD spring, we use those in some 41mm forks
that have thicker tubes, like the original Kawasaki Concours and the
Yamaha FJ1100.
The 1.0 is a bit on the stiff side for you, but ok if you're a fairly
aggressive rider. If not, then 0.95 would be better. 0.05 is a small
difference, hard to feel.
 

Race Tech is same from tech guy. Next size down is 32mm. They suggest light surfacing of the circumference to allow spring to drop in tube.

I was considering this, but talked myself out. Now I am thinking - What have I got to loose? I only need a few thousandths. It may "weaken" the spring rate but that may be OK. It will not cause the spring to fail. 

Now I have to figure out some way to run a tube or rod though it and turn to try to get as even as possible.

I am sure I have done dumber things in the past and gotten away with it.

Quite pleased with results. Within 0.02mm +/-? Hard to measure a spring.

Reduced diameter by 0.40. Fits tube perfectly. Ground, 3M scotch pad, polished. 

[image: 20161118_211032.jpg]

Clever stuff! How did you do that?


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Clever stuff! How did you do that?


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Great news. Looks neat.  :smile:

Yes, how did you do that ?  :unsure:  

RC36Rider, 11/14/2016 at 5:37 PM

Harshness is mostly a function of damping, I believe. For the VFR (and most Japanese bikes), the road to firm and controlled yet plush is heavier springs, mild compression damping and adequate rebound.

And friction: excess static friction will have very much the same feeling as overly stiff compression damping.

I agree 100% with your comments regarding spring rate. Though it may seem counter-intuitive the key to a firm yet plush ride is heavier springs with less installed preload (I aim for around 10 mm). They are also the key to the most desirable handling. Heavier springs with less preload will:

1. give more linear dive on the brakes (esp. when combined with good comp. damping)
2. increase bottoming resistance, and make tuning the total fork travel with oil height much easier.
3. cause the front end to stand up less if the front brake is applied in the corner, making changes to speed and line easier
4. cause the front end to extend less on acceleration, making the bike less inclined to run wide on corner exit
5. give much better feedback about road surface, grip levels etc.

I hope to acheived all 5 points as listed above,....

I was trying to come up with an accurate method to size springs, and then went with use what you got. Slipped spring on dowel rod clamped to bench. While spinning spring, ground surface with 80 grit right angle grinder. Light touch, and watched the flat that was created. Found it was not that difficult to keep even, and checked fit. When I had 3mm flat it seemed good. Switch pad to a red 3M scotch pad to smooth and ease edges.  Went straight to buff wheel and polished.

I measure that I took .25mm off, net .5 clearance. I changed the spring in that measurement by 7%. Can we assume that the spring is now 7% lighter rate? 

Have one assembled. Will do a spring rate check and see if there is measurable change.

If no new setbacks and find some oil, may be rolling this weekend.

[image: 20161118_195718.jpg]

21 minutes ago, veeferbkk

And friction: excess static friction will have very much the same feeling as overly stiff compression damping.

True that. To quote the Race Tech Bible: "Friction: Bad !"  :laugh:

I haven't bothered with friction beyond checking that my stiction (as measured by static sag difference between the forks compressing and extending) was within an acceptable range. Meaningfully improving this is something I consider beyond my modest DIY technical and/or financial means.

By the same token, I don't mention reducing unsprung mass because I can't afford carbon or forged wheels. 

Out for another shake down run today. I boosted the rear pre-load and in all the bike is feels "right". Travel over bumps seems even front and back. Little front dive on brakes. I think the fork project has been a success! May cut the fork pre-load spacers 5-10mm, and then get rear gas up to correct, see how that goes and then pull rear for rebuild? It is close to end of riding season in this part of the world,... Just hate to take it out of commission as I just got it together.

This is really my first impressions of riding a vfr so nothing to compare to. Quite a change from the little FZ 600 I have running. 

Here are photos of the front and rotors on the bike and the spare that I will be mounted new Angel GT on.

If anyone has a clue of what these rotors are please let me know.

Think I will pop the pads just to check them but does not seem that if contaminated they would give the grab/surge affect?

[image: vfr wheel 1.jpg]

[image: vfr wheel 2.jpg]

30 minutes ago, RhodeMoto

If anyone has a clue of what these rotors are please let me know.

Never seen anything like this.  :unsure:

That is definitely not a 4G wheel, though. They are aftermarket floating discs on a 3G wheel apparently. 

Just had another thought: uneven wear of the disc surface (high spots) would cause this. 

Have you checked runout on the whole surface swept by the pads ? Actually, maybe running a fingertip on the disc while spinning the wheel would be enough to feel it (?).

You're probably right about the contaminated pads. That would not cause the grab and release symptom. My bad.

What about the solid rotors on bike now? These are not stock from what I have seen. Not going to matter if the swap works. If they can be ground and trued may be worth hanging onto for spares? 

4 hours ago, RhodeMoto

What about the solid rotors on bike now? These are not stock from what I have seen. Not going to matter if the swap works. If they can be ground and trued may be worth hanging onto for spares? 

Definitely not stock either but that's all I can say about them.

Swapping wheels would probably tell you if it's something wrong with the discs.

Machining the discs is certainly possible but I have no idea where to go or how much that may cost. Friendly machine shop ?

Ok, I am back. Mounted and balanced new angel GT on the spare front wheel. Check rim and found it was very true. Dry fit tire and positioned so only needed 1/2 Oz. Weight. This wheel has floating rotors. 

My front brake grab issue is gone, so not sure what the issue is with the fixed set but clearly the problem. 

So now have good forks, good brakes, but,.........

Now have experienced an odd wobble. Very disturbing. Just happened a couple of times, but felt I might loose it. Going along not excessive. Testing brakes, and sudden shake? Wobble? Did not feel like coming thru bars. As if the whole bike did a side step hop. 

Possessed by demons?

Errr... swap the floating discs to the other wheel to rule out a tyre problem ?  :mellow:

I'm sure you feel certain that you have done it right, that the tyre is new... but no one is immune from error and that also goes for tyre manufacturers and resellers (bad storage method ?)

I know it's a bit of a hassle but a faulty tyre would explain it and I am not aware of any other reliable method to check this. 

Thanks to everyone's support and exchange.

Best wishes for a good new year.

Happy new year to you as well.  :smile:

OK - Now to the rear.

I have pulled the rear and removed tire.

I have two 8 spoke wheels and both are out of round. No visible damage. Both 2mm radially and 4mm laterally.

Anyone have experience and success having wheels trued?

[image: gallery_34381_7701_47073.jpg]

I had this straightened for 100 €.

I got the wheel back straight and true but stripped of paint and deeply scratched.

Been riding on it ever since with no problems. 

That does not look good. If that can get fixed then hope for mine. 

Have not found anyone local. Would be nice to actually talk to person than send off to unknown. 

Looks like I am out of commision again. 

This was to be my newer, reliable bike,.....

Wheel bearings?