Say... I'm kinda thinking on doing the F4 fork swap on my 6th gen over the winter, actually having Jamie D do the fork build, with me then bolting it all together. Starting to look at the cost of gathering up the parts, when searching for calipers & master cylinders on eBay I see some M/C (RC51, CBR929, CBR954, etc..) have remote reservoirs, are there any clearance issues, or fitment issues with Heli bars? Also, how bout that brake light, should it just plug in to any of these M/C and presumably work? Wondering if maybe I should be limiting my search to just F4 calipers and master cylinders, would that be my better path? Been doing a fair amount of reading on the matter and have a pretty good idea of what's in store, but there's always questions. I truly appreciate any insights. Thanks.
Just a note: I think the F4(99-00) used a stiffer spring .74kg and the F4i(01-up) used a .66kg, not that that matters if your springing it to your weight!
If I'm not mistaken many CBR's all use the same brake M/C as the F4/F4i and calipers too. I think it's F4i, 929 and ? using the same .
Yes the brake light switch will work with any two wire switch.
Not familiar with remote brake res clearance.
I'm assuming you plan to use the Heli bars? Don't forget that the F4/F4i forks are an inch or two shorter and at stock settings there won't be much fork sticking up above the top triple. Think it's about a inch.
Just a note: I think the F4(99-00) used a stiffer spring .74kg and the F4i(01-up) used a .66kg, not that that matters if your springing it to your weight! If I'm not mistaken many CBR's all use the same brake M/C as the F4/F4i and calipers too. I think it's F4i, 929 and ? using the same . Yes the brake light switch will work with any two wire switch. Not familiar with remote brake res clearance.
I'm assuming you plan to use the Heli bars? Don't forget that the F4/F4i forks are an inch or two shorter and at stock settings there won't be much fork sticking up above the top triple. Think it's about a inch.
BR
Ok on the brake light, good news there. Yes, want to keep the Heli bars. Understand I am not a suspension guy... at all, but here's how I understand that it's suppose to work, Jamie D takes my 6gen forks, uses some of my current parts, RT Gold valves, springs (least I think, springs? - I have a .95kg now) upgrade the rebound valves, swap out to F4 lowers & new caps which allow for comp/rebound adjustments.
Well, according to the "World's Foremost Authority on Such Matters" (i.e., me :tongue: ), master cylinder and caliper piston diameters vary widely among the various CBR900RR models, so while they are swappable, they are not the same. It is therefore still important to match the master cylinder and the calipers, with the easiest way to do this being to use a set from the same donor bike or model.
Well, according to the "World's Foremost Authority on Such Matters" (i.e., me :tongue: ), master cylinder and caliper piston diameters vary widely among the various CBR900RR models, so while they are swappable, they are not the same. It is therefore still important to match the master cylinder and the calipers, with the easiest way to do this being to use a set from the same donor bike or model.
Ciao,
Yep, that's what I was planning, keep it matched. Me thinks it's may be best for me to stick with the F4 parts for this project, least that's what my gut tells me. Just to much lack of knowledge on my part to venture to far astray. Still reading and trying to learn.
I really wasn't very clear about what I was up to with my topic header, not doing a complete F4 swap, just the lowers. With that, BR brought up fork length, something that I never even considered! This is where my lack of knowledge comes into play. Well, now I guess my next question is... could anyone tell me what the overall length of the forks will be doing just the F4 lower swap? I was figuring on lower the front a bit, just not as much as what BR brought to my attention by doing a full F4 swap. Yikes! I would've been in for a surprise!
Using VFR tubes in F4 lowers will eliminate any issue with fork length. Jamie will just install the F4/F4i cartridge into the VFR upper/F4 lower which will provide you both rebound and Comp adjustments and longer tube length for your clip-ons.
Using VFR tubes in F4 lowers will eliminate any issue with fork length. Jamie will just install the F4/F4i cartridge into the VFR upper/F4 lower which will provide you both rebound and Comp adjustments and longer tube length for your clip-ons.
BR
Thanks for your help BR! I'm a fairly disappointed with myself for not thinking this stuff through and researching it better.
One option that gets overlooked is to just drop the F4 internal cartridge into the stock 6 Gen tubes and use the 6 Gen lowers. You need to use the stock VFR cartridge tube if you want to retain the same fork length. This way you can still use your linked brake system. I have ABS and did not want to screw around with the entire system.
I did this modification on my bike with a slight twist - I modified one cartridge system to provide only compression damping with adjustment on the top cap. I then modified the other cartridge system to provide only rebound damping with adjustment on the top cap.
If you take the time to understand the hydraulics, it is actually pretty easy to make the modifications without going to the machine shop. I am completely satisfied with the modification and the range of adjustment on both fork legs. You have to develop your own custom valve stacks because each stack is doing twice the work - sort of. I used RaceTech high frequency rebound stacks as the basis of my custom valve/shim stacks. Of course you can't use there charts because they are not relevant to this type of modification
I put a complete F4 front end (brakes and all) on my '96 VFR and much prefer the F4 brakes. But like I said, I did not want to screw around with the LBS and the ABS. I actually wanted to keep the systems working correctly.
That's a great option and has been done many times(btw they use F3 cartridges if 5th gens also).
This method provides rebound adjustments using all stock VFR fork pieces other than the cartridges.
BR
Yup - it's pretty easy to do! What intrigued me the most was creating a compression adjustment on one of the fork legs using the top cap rebound adjustment system.
Having both rebound and compression damping adjustment while retaining the VFR lowers was important to me.
"I did this modification on my bike with a slight twist - I modified one cartridge system to provide only compression damping with adjustment on the top cap. I then modified the other cartridge system to provide only rebound damping with adjustment on the top cap."
Please expand on this mod creating comp adjustments, many of use would like to know how it was done! :ph34r:
"I did this modification on my bike with a slight twist - I modified one cartridge system to provide only compression damping with adjustment on the top cap. I then modified the other cartridge system to provide only rebound damping with adjustment on the top cap."
Please expand on this mod creating comp adjustments, many of use would like to know how it was done! :ph34r:
Ya know, as I was performing the mod, I was thinking that I should have documented it with pictures and such. But I only had one afternoon to complete the entire job because I am using the bike to commute during these Summer months.
However, I still have an extra set of F4 internals on the work bench. Let me see if I can use them to create a work instruction. It may take a few days to do a decent job. Please be patient ;-) I'm happy to help!
With that said, I can offer a few clues as to how to go about the transformation.
Let's start with the leg that you will turn into the compression damping leg. You use the F4 cartridge rod, rebound valve (I used RaceTech rebound valves), fork cap and adjuster rod. All of these parts will be used with the stock VFR cartridge tube.
Now here are the critical mods. You must take the rebound valve body and turn it around on the cartridge rod so the shim stack is now on the top side of the valve body. This is because it will now be used to bleed off hydraulic pressure as it moves down into the cartridge tube. You also need to eliminate the bypass check valve on this valve body so it does not bypass fluid as the valve body travels back up the tube. This next step is very important. You need to drill four 3mm holes at the top of the cartridge tube so that all of the fluid pressure can bleed off out of the top of the tube as the valve moves back up. The position of the four holes is important because you don't want to drill the holes in the area that the Teflon seal travels on. This is why I need pictures - but I think most people could figure it out.
As the cartridge rod and valve are moving back up the cartridge tube, fluid will be drawn up through the check valve shim in what was the compression valve body at the bottom of the tube. The next step is important as well. You will block off the original compression shim stack so that it can no longer pass any fluid.
Basically, you have now made a hydraulic system that is sealed as the piston travels down the tube and bleeds the pressure through the bleed screw adjustment and the newly designed valve stack. The new holes at the top of the tube along with simple one way check valve that you have constructed at the bottom of cartridge keep the cartridge full and circulating.
Now for the rebound leg. This is much simpler because it is already designed to operate as a rebound damping valve. The trick here is to reverse the compression base valve on the bottom of the cartridge so you can take advantage of the larger oil passages that are normally used for the check valve circuit. You then want to use just one light compression shim so that it acts more like a bypass check valve than a compression valve. The idea is to let the cartridge pressure bleed off easily while the damper rod is moving into the cartridge tube but creating just enough pressure to assure that fluid is moving through the check valve in the rebound valve so that the area above the rebound stack is always free of any air.
I know that without diagrams, this may be hard to understand - I should have taken pictures. There are a few more details related to the fitting of all the components that I did not get into. But most mechanical minded people would be able to figure it out.
Honestly, the hardest part was guessing at the shim stacks to use. However, I have had about 20 years of experience re-valving suspension on all kinds of dirt and street bikes. So my first attempt was pretty close to what I wanted. I am very pleased with the results.
Anyway, I hope that this was not too confusing - it's late. I'll see what I can do about creating an annotated work instruction - can ya tell I'm an engineer ;-)
Who knows - if I do a good enough job, maybe it will become a sticky!
Cool, so you've basically done what many new superbikes have done making one fork Comp and the other a Rebound fork!
Once you explained it a little it's pretty easy to see how/what you have done, thanks for your creativity and sharing it here!
Cool, so you've basically done what many new superbikes have done making one fork Comp and the other a Rebound fork!
Once you explained it a little it's pretty easy to see how/what you have done, thanks for your creativity and sharing it here!
BR
Yep the Ohlins full cartridge kits that replace the standard cartridges for example the CBR1000RR all have compression adjustment only one fork leg & rebound the other.
Honestly, there isn't really a lot to be gained by separating the compression and rebound functions between the two forks. Having external compression adjustment sounds nice, but it isn't nearly as effective as the rebound adjustment. You will get 80% or more of what you need with just the rebound adjustment only. The compression adjustment gets you the last 10-20% - helpful mostly for track riders.
I am the last 10% to 20%...so having external adjustment at the track is exactly why I want this...but in general, most of us set it and forget it for street riding.
[quote name="JamieDaugherty" post="928644" timestamp="1389789106"]The compression adjustment gets you the last 10-20% - helpful mostly for track riders. Just some advice!
I'm really slow...I'm putting F4i forks on my 5 Th gen and am not reusing 6th gen lowers like you guys. I'll keep it simple and just do my comp adjustments on the F4i lowers and de-link my brakes.