More Complex Than What I Am Used To...'86 Vf500F

Hi, new member here. For years I have been playing with 1970's sohc Honda fours. Lately, I have had the itch to go a little faster. So, I thought I would find myself some kinda '80's/early 90's sportbike. A couple weeks ago I stopped by a vintage bike shop that I am friendly with and the owner's son offered up this '86 vf500f, a stalled project. The asking price was way right, so I bought it. Here are some pics back at my garage.

The previous owner's story is that he had cleaned and lined the tank, cleaned the carbs, and got it running but he suspected it needed coils, as it would miss above 5000rpm. All this a little over a year ago. He supplied used coils from a parts bike and told me he wanted to keep the parts bike but if I needed anything else, it was available.

So I installed the spare set of coils, charged the battery, and attempted to start it up. It was very hard to start and would only run with the choke on and would not accept any throttle. Also, it was only running on 3, sometimes 2, cylinders. Sounded like dirty idle jets to me, so I figured I would have to pull the carbs.

The complexity of this bike was intimidating to me after working on '70's Hondas for all these years, but I bit the bullet and dove in with the aid of a Clymer manual. I found the machine to be amazingly well engineered and surprisingly easy to work on, but now I am somewhat stuck.

The carbs were found to be filthy inside, as fuel must have been left to sit in bowls, absorb water, and then evaporate. All 4 idle jets were plugged, and even 2 main jets. I also found moisture and corrosion had found it's way into the carb tops over the cv diaphragms. So I cleaned everything up. I made considerable effort to blow carb cleaner and air through every passage, but these are much more complex than what I am used to and I have never had much success with cv carbs.

So I got it all back together and started it up. All four warmed right up, and it settled into a nice idle, revved good in neutral too. I attempted a test ride. ...no power Spent some time with the mixture screws and got it running quite smooth at idle and up to about 1/3rd throttle...anything above that and it has no power.

Not quite sure how best to proceed from here. First theory is that there are still some clogged passages in the carbs preventing the slides from behaving as they should. Or is it ignition related? This really acts like an old cb750 that has a stuck ignition advancer...but I am guessing ignition advance is controlled electronically on this by what? ...and how can I test it without mindlessly swapping parts that are probably nla anyway? The bike starts and idles great, and feels strong taking off in first, but then any more than 1/3 throttle position in any higher gear and there is just no power...no bogs, no misses

Thanks for reading and any ideas are greatly appreciated.

Plugged fuel line/filter? That would be my first thought, especially if she goes in 1st, that or it could also be vacuum related, cracked hose? Good Luck!

I had an '85 VF500F, my first bike. When it was hot out and I would shut it down, upon restart (could have been hours later), it would sputter and stall out on me over and over again. Nearly killed myself trying to get off a ferry between Long Island and Rhode Island on it's diamond plate ramp.

Turned out there's a vacuum diaphragm at the bottom of the tank which only lets fuel flow when the engine is running. That diaphragm had rotted out and would no longer reliably open the valve under vacuum. Why it happened sometimes and not others is still unclear. Since you're having luck with carb adjustments, I'm guessing it's a different fueling issue though something to check.

Personally, I agree with V-FORE: check fuel filter and fuel pump pressure. (I believe it has a fuel pump... man it's been a long time...)

download the manual,, :fing02:

http://www.vfrdiscussion.com/forum/index.php/files/file/222-clymer-vf500f-service-manual/

gll429

download the manual,, :fing02:

http://www.vfrdiscussion.com/forum/index.php/files/file/222-clymer-vf500f-service-manual/

Don't bother with the Clymer. Download the Honda Service Manual. It's for the magna version, but engine and everything will be the same.

http://www.vfrdiscussion.com/forum/index.php/files/file/192-vf500-c-service-manual/

Do a compression check. I got mine running and idling fine, even though there was a hole in one of the pistons.

I do not think I have a fuel supply problem and it does not really act like a vacuum leak either, but I will try some more double checking. This bike just has a vacuum operated petcock, which I have checked with a vacuum pump. Fuel flowed strongly at about 2-3psi and held long enough to drain 1.5 gallons from the tank. I have removed the EPA anti-tamper plugs over the mixture screws so passages can be cleaned. Would these leak vacuum or something if not replaced? I already have the Clymer manual and it is useless. I am pretty sure the '86 has significantly different carbs from the 84-85. Thanks for the link to the Honda manual as it has some better info on the ignition system. I really should figure out the necessary hardware to do a compression check though I can't see it having a holed piston. What is best to use for a spark plug wrench? I have had all 4 plugs out, but it is a slow painful process. The factory tool kit is there, of course missing only the spark plug wrench.

Pull the valve covers and check the cam lobes and set the valve lash if ok.

Valves are another major issue with these bikes. Bad valve spring design. Need to check the valve clearance often. The 2 engines I've had all had an exhaust valve smashed to bits, and the good valves were all out of spec. I think my 250 (which is just half the same engine) is the same way.

I will check out under the valve cover. Can the lash be checked and set with normal feeler gauges and hand tools? I am finding a lot of stuff about special Honda tools but all the pics I am seeing look very similar to Honda's good old screw adjusted tappets.

Yep. Just a flathead screwdriver and a 7mm wrench IIRC. There's a trick where you turn the engine over a bit to put some pressure on the tappets, and then tighten down the nut. Keeps the tappet in place better than trying to hold it steady with a screwdriver, and it holds both of them down.

YoshiHNS

Yep. Just a flathead screwdriver and a 7mm wrench IIRC. There's a trick where you turn the engine over a bit to put some pressure on the tappets, and then tighten down the nut. Keeps the tappet in place better than trying to hold it steady with a screwdriver, and it holds both of them down.

Man thanks! Did not know that and have been struggling to get the gap right on my VF750

Team Bongo President

stupid question, but did you sync the carbs?

schwarzc

stupid question, but did you sync the carbs?

not a stupid question really (except that I already answered this question earlier in the thread)...I did bench sync them. I have not vacuum synced them. Earlier I asked how critical this is with these cv carbs. It is not critical at all with the standard slide carbs that I am accustomed to working on.

Oh, okay, .... sorry, the bench sync must have slipped my attention (or my abilities of the english language :goofy: )
So, yes - carbs, that are basically synced normally behave better than that.

my next steps would be compression test of all cylinders (already mentioned here), and, since you alreday swapped the coils, a swap of the CDI.
I´d check the valve clearance after all that, since this is a relatively huge operation.

Just another little advice: For carb cleaning, I had good experiences with acetone.

BUT! remove ALL plastic/rubber parts before, or they might be gone or damaged beyond repair! (I have to mention this, .... )

Thanks for the tips. I do have access to another pair of unknown good cdi's. What about the pulse generators? Manual says ohms should be between 315-365 ohms. Mine measure about 400 and timing on the one I could get my timing light on is maybe 3-4 degrees off, but does look like it advances with rpm properly.

Thanks

Welcome!

VF500F Interceptors are great bikes but they do take a bit of mechanical skill to keep them running in tip top shape.

V4 carbs are indeed a beautiful thing - cross section drawing from Motorcycle Mechanics Magazine, July 1984.

[image: v4carburetordiagramfrommotorcyclemechani]

As mentioned the Honda Factory Service Manual (FSM) is a must have for the library shelf. Check on eBay for one in the green binder:

[image: fsmvfrworld10-13-10.jpg]

As a start to diagnosing - I would recommend completely disassembling the carbs.

This is the only way to insure everything is 100%. If this is outside your skill set - Mike Nixon is a great source for a pro rebuild - it is expensive but it is worth every penny! Mike also offers an illustrated tech manual if you would like to tackle this yourself - it is filled with great intel on how to rebuild these carburetors & really a must read.

A link to Mike's website:

http://www.motorcycleproject.com

When rebuilt - install the carburetors with new OEM boots. Lubricate and tilt the boots as shown below and push straight down on the carbs - do not use a hammer or strap, etc.

Tilting the boots and a little oomph is all you need to seat these correctly.

[image: vf500ftiltingthebootsbeforeinstallingthe]

Sync the carbs using a quality manometer (Morgan Carbtune is a great option) - this is very important! You'll need a few special tools for this especially the Factory (or similar) wrench (bottom photo). This wrench will make your life much easier.

[image: vf500fcarbsync03-30-11.jpg]

[image: vf500fcarbspecs08-10-10.jpg]

[image: vf500fcarbadjtoolvfrworld.jpg]

Once you have the carbs installed take the bike out for a test run. Hopefully everything will be in order. If not you can cross carbs off your list and move onto the next suspect.

Good luck - and let us know how you make out!

Great advice from IC(hey stranger). I'm leaning towards carbs being the problem. You do not need to separate them from the intake plate to get a good cleaning, in fact, don't separate them. Verify with a guitar string or similar that you have flow, can't always rely on carb cleaner through a straw to clear blocked passages. Did you remove and clean the screens under the float needles? Don't mix parts from different carbs, they are not the same from front to back. The mixture screws under the factory plugs have very small o-rings and washers and can easily be left in the carbs and shot out wlhile cleaning.

Great looking bike btw, It looks pretty darn nice in the pics. IC and others are great help with this bike so don't be afraid to hit them up for advice. Keep us posted.

IC, that was a very informative post. Thank you very much...Kel too. I felt like I did a pretty thorugh job of cleaning the carbs, but one thing was pointed out that I did not do...I did not realize there were screens behind the needle seats. I am gonna have to pull the carbs again to do valve clearances and I will double check everything. I am terrified of separating these carbs from the rack. Is there any way to bench test proper operation of the cv diaphragms?

Shout out to Kel!

seanbarney - I'd take a read through Mike Nixon's book on rebuilding V4 carbs. It is Must See TV & a great resource. With this as a guide you'll have all the intel you need. I opted for Mike to rebuild my set but I also have his book - which contains invaluable information on how to service these carburetors.

For the lash - two feeler gauges and the proper tools will keep you in good stead.

OEM tools:

[image: oemvalveadjtoolsvfrworld04-11-11.jpg]

square head on VF500F adjuster:

[image: vf500f85head8mmtappetlocknut11-10-10.jpg]

tools in place:

[image: DSC06516_zpsbcc7df7b.jpg]

two feeler gauges are key:

[image: detail_zps546881a7.jpg]

Good luck & keep us posted on the progress!

What did I tell ya ^^^^.

If the the engine will not rev high, it is possible you have a torn cv boot or it is not seated/sealed at the cap. A way of testing this is to (carbs assembled) lift the slides with your fingers all the way up. Then let them drop. They should slide slowly down and evenly. If they fall quickly you could have a torn boot or they are not sealed correctly under the cap. Even a pin hole in a boot will cause problems.

Separating these carbs and a sonic cleaner is the best way to clean them.

If you have not removed all the jets, choke valves, idle jets/screws they are not clean.

Do not clean the boots with carb cleaner, it will harm rubber.

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Time for updates...swapped in some used pulse generators. These stilled measured out of spec, but were closer than the ones I had. Seems like they maybe helped a little, but the bike still ran like crap. Over on the left you can see the parts bike I have available...

I would suspect the diaphrams as well. I know nothing about those carbs but I have had bad diaphrams on other bikes and they idle fine but just don't go. You are adding air but no fuel.

I HATE the look of that blue goo. Hope none of it is floating around blocking passages in there.

Best of luck!

So, I was back to the old carburetor drawing board...I pulled them off again and once i got the float bowls off it became obvious that I did not clean these carbs good enough the first time, as 3 out of 4 slow jets were at least partially plugged again. I knew these carb bodies needed to soak, but I still did not want to take them off the plenum. So, using a Gunk brand bucket of carb cleaner, I tested soaking some spare o-rings and plastic parts for 2 hours, and as they came out ok, I figured I would be safe to soak 'em for up to 2 hours. So I got some disposable aluminum cooking pans and molded them around the carbs after removing anything that I could without removing the carbs from the plenum, and dumped the carb cleaner into the pans, submerging the carbs. I let them soak for an hour and a half. I was amazed at the amount of crud that came out. I rinsed all passages with spray carb cleaner and blew them out with compressed air and re-assembled.

I then continued tearing the bike down far enough to set the valve clearances. They were all set slightly tight, and I am guessing a previous owner had mistakenly used the '84-'85 specs. I just used 2 ordinary feeler gauges, a regular combination wrench, and my fingers to turn the square drive tappet adjusters. Sometimes it took a couple tries to get the tappet to stay put while tightening the locknut.

Once I got everything back together, the bike started...and...is running strong! I have not gotten to ride it more than about 20 miles yet though due to bad weather here in Michigan...plus some scary worn out old tires and a very leaky fork seal...so that stuff will be replaced next. Hopefully I will get some acceptable weather for a longer ride sometime before April.

I still need to vacuum sync the carbs but don't know how to find the necessary adjuster tool. The guys at my local Honda Parts Dept. were of course clueless. What is the Honda part number? Or is there a Motion Pro equivalent or something?

Thanks everyone for all your help and information so far.

JimGregory

I would suspect the diaphrams as well. I know nothing about those carbs but I have had bad diaphrams on other bikes and they idle fine but just don't go. You are adding air but no fuel.

I HATE the look of that blue goo. Hope none of it is floating around blocking passages in there.

Best of luck!

diaphragms turned out to be fine

Just buy the motion pro carb sync. Its the best investment you can make with carburated motorcycles. I just use a 1/4" ratchet and sockets with a swivel joint to reach the adjustment screw on the carbs.

Magna86

Just buy the motion pro carb sync. Its the best investment you can make with carburated motorcycles. I just use a 1/4" ratchet and sockets with a swivel joint to reach the adjustment screw on the carbs.

duh...now why didn't I think of that. Thanks

Great thread and info coming in here that I will find useful when I pick up a 86 VFR 750 I bought early next year. What, It's not Fuel Injected!!!! What the hell is a Carburetor??? :wacko:

Great support guys! :cheerleader:

BR

Pics please Baileyrock.

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JeffInFranklinTN

Pics please Baileyrock.

Sent from my iPhone using Tapatalk

Really?!?.... Well, OK...

[image: gallery_19432_6525_231353.jpg]

BR is the good lookin' one with his arm around the hot umbrella girl....

Hot Umbrella girl threadjacks are always welcome, by the way...

seanbarney41

Hot Umbrella girl threadjacks are always welcome, by the way...

My apologies for the momentary threadjack... when I read Jeff's post and I thought... well, I was tired and it cracked me up :laughing6-hehe:

ok, I figured out how to post pics here...again. So time for a long overdue update. Crusty rubbers above replaced with these...

[image: 18129553512_e64d86bf11_k.jpg]DSCN0480 by Sean Barney, on Flickr

mmm...new chain and sprockets too, stuff is mostly cleaning up ok

[image: 17945115718_7125b414c3_k.jpg]DSCN0485 by Sean Barney, on Flickr

despite the appearances in the earlier photos of this thread, this bike is not pristine, has been crashed and beat upon pretty hard but has survived...some of the ugly's in the fork seal replacement process...

[image: 18129558712_ab166a1847_k.jpg]DSCN0479 by Sean Barney, on Flickr

soaked with fork oil

[image: 18106560586_758f572bc2_k.jpg]DSCN0478 by Sean Barney, on Flickr

[image: 17945170658_43947a11fa_k.jpg]DSCN0475 by Sean Barney, on Flickr

kinda scary

[image: 17510487334_5cecaa58a9_k.jpg]DSCN0474 by Sean Barney, on Flickr

but I got it all put together and have been having good times on this bike

[image: 17944975188_5b3896a939_k.jpg]DSCN0512 by Sean Barney, on Flickr

have done about 3000 miles so far this season...after some late night street fightering

[image: 17943679758_c14401f46b_k.jpg]DSCN0572 by Sean Barney, on Flickr

Leelanau Peninsula, just off M22, some of the better riding in Michigan

[image: 17943583938_1301c0ab31_k.jpg]DSCN0590 by Sean Barney, on Flickr

yes that's a dead fish in the Bloody Mary

[image: 17510928023_7a67bb1716_k.jpg]DSCN0588 by Sean Barney, on Flickr

'lil 5 hundo can hang with big bad Buells in the straights and spanks 'em in the twisty's

[image: 17945276479_31175fb07b_k.jpg]DSCN0584 by Sean Barney, on Flickr

Congrats! How did the carb sync work out - & if I can add, don't forget to check the valve lash (if you haven't done this - it's very good to check this off the maintenance clipboard). Have fun!

Nice work!

Glad to see you got her fixed up and out enjoying the roads :D

BTW... that drink looks like one hell of a hangover cure... though, I may just stick with the headache!

InvisibleCities

Congrats! How did the carb sync work out - & if I can add, don't forget to check the valve lash (if you haven't done this - it's very good to check this off the maintenance clipboard). Have fun!

Rush2112

Nice work!

Glad to see you got her fixed up and out enjoying the roads :D

BTW... that drink looks like one hell of a hangover cure... though, I may just stick with the headache!

Rush2112

JeffInFranklinTN

Pics please Baileyrock.

Sent from my iPhone using Tapatalk

Really?!?.... Well, OK...

[image: gallery_19432_6525_231353.jpg]

BR is the good lookin' one with his arm around the hot umbrella girl....

AMA Super Bike races at Barber, I remember that was a great time! :beer:

Nice 500 BTW! :wink:

Great jobb! I have to say I might like that non full faring version more than the one I have......