1986 vfr750f fuel/air mixture screws

I bought this 750 a short while ago and I have been fighting with it since. I finally had it running pretty decent after cleaning the carbs but the RPMs would float at ~3k after a rev, which I found on here is probably an air leak. I dug deeper and found that 3 of the orings for the fuel/air mixture screws were either missing or broken. A couple of the washers are missing as well. Does anyone know a source for these? I don't want to buy an entire carb rebuild kit for each carb when all I need is the oring/washer. I measured the one oring I do have and it appears to be 3mm id 5mm od and like 1mm or 1.5mm wide. The washer measures about the same but much thinner (I really need to get a set of calipers haha). I also considered just buying aftermarket fuel mixture screws since the head on one of mine had to be reglued to so I could adjust it, but I don't see any specifically listed for vfrs. I read if I say TOECUTTER TOECUTTER TOECUTTER a carb guru will show up Any help/info is greatly appreciated. Thank you.

 

Figured I'd tell a little more about the bike since I never did a "look at me" new member post when I bought it. 86 750, has a (looks like) homemade 4-2-1 that I need to do some clean up welding on and recoat as well as cutting off the crappy frame welded hanger and putting on a proper one. It has a termignoni pipe and it sounds amazing, the sound was the selling point at $850. Rear brakes were locked when I bought it, tailgate strap broke when we were unloading it and the shock broke the rear brake free haha. I replaced the rear rotor (it was SHOTTTT) and the pads. With a fluid flush the rear brakes seem to be fine. Front brakes are dragging and I've replaced the brake lines with new galfer stainless braided, rebuilt the MC, and cleaned the calipers. Now waiting on fresh seals to arrive; since they're still dragging I'm doing a complete rebuild. One carb float bowl leaked, found out a 75mm oring fits on this website and went ahead and replaced all 4. They fit perfectly. I have vfrchuck front fairings (upper/lower) but the upper fairing is cut slightly crooked for the headlight I think. I had to unbolt the 2 headlight bolts (the ones directly behind the headlight) to get the rest of the bolt holes to line up. Also possible that the fairing stay is bent and that is why the fairings don't line up perfect. The bike appears to have been downed, then the PO bought VFRChuck fairings, then downed it again. I love this bike though and cant wait to make it into a decent budget commuter/canyon monster. I also have a 2014 fz-09 (new yamaha 847cc triple. Similar torque curve to the vfr, table from 2k rpm up) and my wife has a Ninja 250. I had a 1985 cb700sc (amazing bike) but it was very rough and I could only polish a turd so much. Once she started burning oil at 85k miles (I bought it 3 years prior with 72k) I sold it and got this project. I originally thought this was a canada import but I think its a US 750, the odometer and trip meter appear to read in miles, but theyre a little off so Im not sure if its reading miles higher than accurate or km lower than accurate. 60k on odometer.

 

Interesting note, on the title the bike is listed as being colored purple.

 

Don't assume that air leaks are keeping the idle speed up until you've tried an accurate carb synch with the engine hot.

With all the misalignment you mention, it's important to make sure your headlight is aimed correctly according to standards. One knob adjusts vertically, the other horizontally.

If front calipers are dragging, try cleaning and lubing the 2 pins on which they slide.

 

The floating at 3K rpm may be related to lack of o-rings on pilot jet screws. Under deceleration air could be getting sucked into the carb. Could also be out of sync.

Have you looked locally for those tiny washers and o-rings? Hydraulic repair shops tend to keep o-rings of all sizes in stock. They tend to carry those carb bowl sized o-rings as well. You could also try a local bike salvage place and see if they have any new or used ones. If they have a junk set of carbs, you might can salvage the parts you need from them.

I would tear down all 3 brake calipers and clean them and inspect the pistons for corrosion. Make sure the tiny relief hole in the master cylinder is clear. They tend to clog and then the brakes get stuck. Don't skimp on brakes, they save your life, man.

 

The idle isnt an issue, just the floating rev it has for ~1-2 seconds while the rpm returns to idle Squirrelman. I didnt look at the pins the first time I cleaned the calipers, but when I took them apart this time I noticed gashes in the pins where the pads had been resting. I filed them down then smoothed it, but may just buy new ones. Undecided as of yet. Slightly worried about rust primarily. I figure any paint I put on the pins will just rub off. Maybe a good coating of water resistant grease?

Jason I hadn't thought of looking at one of those shops for the orings, thank you. We don't really have motorcycle scrap yards where I live. Not many people ride since the roads are wet more than they're not. I bought this bike with zip ties holding on the fairings and many many many bolts missing. If it wasn't for the local hardware store having an amazing selection of fasteners I don't think I'd have been able to reassemble it.

 

I had a similar problem with a slow drop to idle. Made the bike maddening to ride, since it'd drop under load suddenly. I sold the bike before I figured it out though. I'm told it's an air leak too. New carb boots were next on the list, but I found that half the problem was mis-routed throttle cables. They were worn and if I had them even a ~little~ too tight, the throttle would stick. I re-routed them per the workshop manual and loosened up the adjusters; it really helped and the price was right.

Even if you find some used carbs, those rings are mashed up 99% of the time. I'd send you my old ones for postage if they were in any kind of useful shape. I do have the washers if you need a few, along with some spare needles. I have three bodies too, but they're Cali model carbs, not sure they'd help you.

You sound like you know what you're doing...so no offense intended here...but just to be sure...are the o-rings they're installed in the right order on the needle? It's spring, then washer, then o-ring. I've found the occasional carb that had two washers from just that problem. One of them cracked the bleed tip off and ruined the whole carb body, ugh.

I always use a very thin coat of Liqui 508 copper anti-sieze on the brake slides, bolts & pins. It's a little pricey, but it's never failed me. I also use it on wheel lugs and auto break rotor faces too, great stuff. Very temperature resistant, although it's not as water resistant as white lithium or moly greases.

I always really liked the Nighthawk S too. I haven't owned one yet...although there have been a few close calls... :cower: They're such a pretty bike (even the RWB) but the starter clutch tensioner and thrust bearing problems have always kept me away from them.

 

Desktopdave - Mine doesn't spontanteously drop or have any ill effects except running a bit warmer than is common of these bikes (running lean from sucking air I assume). My carb boots were pretty stiff when I first took them off but they all look decent and are crack free. As far as the oring washer order, no offense taken. I actually have no idea what I'm doing, I learned most of what I know from websites like this one. I learn from necessity. The two that were in there were in the right order but the other two carbs had no oring at all and one of the two I had was missing like a 1/4 of it. As far as antiseize, I'm hoping to use this bike as my work commuter (a beater to ride to construction sites) and it rains a lot here. It would probably get washed off. Thank you for the idea though.

The most common issue with the nighthawk s is losing second gear. The other issues are pretty uncommon. Mine, at 85k miles, was somewhat starting to have issues getting into second gear at WoT. Otherwise, it didnt really happen. But to be fair, mine was my learning bike, I rode the piss out of it for 10 of my 12k miles of having it, and the guy before me also learned on it. It wasn't maintained as much as it could be, likely missed a few oil changes before I got it. Once it started burning oil pretty bad I pretty much stopped changing the oil and just topped it off every now and then. I will happily buy a nice RWB 86 asap though. I've only seen one for sale around here in the past 3 years and it was gone FAST.

 

http://www.ebay.com/itm/like/231262738293?lpid=82&chn=ps
I am assuming the orings and washers will be pretty similar and could work but I want to see what you guys think before I wager on only my own (small) bowl of knowledge.

 

Everyone knows this, right ??: Most "missing O-rings" are still stuck firmly to the needle seat and haven't come out; and it takes a good flashlight and good vision to see them still stuck in place down in that deep, dark hole. Best tool i've found for extracting a stuck O-ring is a long wood screw with the proper point and size.

 

Assuming the original o-rings are missing and not hiding in the holes, this kit should work just fine. So if the delivery time is not a factor, then this looks like the best best. You get the washers as well, bonus.

I was at Harbor Freight today and I saw some O-ring kits they have. Check the pics.

 

Squirrelman - I thank you for your insight, you know much more than I do about these bikes (most of what I've learned has been from you, toecutter, or a couple of other frequent posters), but I know the shiny reflection of metal when I see it. Unfortunately the 2 orings are truly gone, as are a couple of the washers. This may be surprising for a well cared for bike, but as I stated earlier, this thing was held together with zipties when I got it. The previous owner wasn't the best. I was VERY thorough making sure that they were indeed missing. A magnet and a nail work pretty well for getting the washers out. I got the one solid Oring out with a toothpick, the broken one just fell out.

Jason- Thanks. I hadn't thought to check Harbor Freight, but I went ahead and ordered the ebay kit. I looked at it more and saw that it's listed as being the same size on the listing. I'm sorry I'm normally more thorough than that...

 

Finally got my washers and Orings today. USPS sent them on the wrong plane and delivered them to the east coast instead of the west coast, delaying them a week -_-. Anyways, shes MUCH healthier now. Now if only my brake parts would get here so I can test ride... [video]https://www.facebook.com/video.php?v=817820014922417&l=9153291924173659257[/video]

 

That sounds pretty good.

Let me suggest reinforcing those cracks on the tail section. Eventually the tail will break off, then it's a lot harder to repair. Mine broke off while riding and was dangling by the tail light wires. Not good.

 

It doesnt look like it, but the crack is fixed. Full penetration plastic weld with some donor plastic. its rock solid I just need to finish sanding the tail and mid fairings so i can paint them to match the rest. THEN, I can start doing the RC30 paintjob on it

 

Good to hear.

 

Just thought i'd mention this for beginners, not necessarily you.