84 vf500f continuing carb frustration- i am at wits end

After many attempts, thoroughly cleaned the pilot jets, after warmup will now not idle below 3000- starts easily, choke is full off- I have backed out the idle adjustment so far there is no tension on the spring, throttle snaps easily back, no way to get it to the pilot circuit, idle screws at 2 1/2 turns, checked the choke return, pulling the lever back to rest position- I have NEVER had so much trouble getting something to run right- this all after having it running well and then sitting too much- pilot jets were clogged at the inside orifice and I have those open now- PLEASE someone direct me- Thx

 

Seems like it could be an air leak around the mounting boots, loose clamps, lost a synch screw spring, float level way off. You did a bench synch before mounting them up ?? Any drippages ??

 

Throttle cable adjustment? Choke linkage not allowing the plungers to seat? Air leak?

 

I had to get off this and got to work- I will do some more checking- carbs have never been off the plenum, have always been in synch, last set of symptoms was a drop off to nothing when revs came down to the pilot circuit- slow jets were clogged some, so I thought I found the issue- boots are in good shape but I will check the clamps- thx for your replies- more later

 

No leaks, float levels unchanged from when it was running well, Viton needles, fresh float bowl gaskets, started instantly on the last go around, just wouldn't idle- slow jets were fuzzy, thought that would be the cure, now a new problem- more later

 

since it's running rich (starting with no choke, easy/ high idle) the choke circuit is suspect. I would disassemble and MAKE SURE that the o-ring the choke plunger seats against is still there and healthy

If it was a jet issue, aside from not having one in, or having one that has huge jet holes opposed to stock, then it would run lean. If it was a sync issue, start would not be that easy, and likely would run lean.

Did you disassemble the choke system when you worked over the carbs, or leave it as is? If left as-is did you then chem-dip it, possibly annihilating the choke's seals?

 

Thx- carbs have never been tanked with O-rings in place- choke circuit has always worked- so if the chokes are at fault, this is a new problem- on startup this time, I had it to the pilot circuit a couple times, but by the time it was fully warm, choke off, I got the 3000 rpm idle- now I have to get back to the baseline idle screw adjustment, which of course you cannot see with carbs in place- book says to point the butterflies at the pinhole in the bore, and that has always worked- all the chokes have been free and return under their own spring pressure- I will re-examine and let everyone know- thx again

 

Is There An Oring That The Choke Plunger Seats On? I Would Think Fuel Mix Oring Is Missing Or Float Level. Just Rebuilt My 86 Vf500 Carbs Which Didnt Have A Choke Seat Oring.

 

This AM- re-adjusted for baseline butterfly opening- started instantly on choke- was able to back off choke opening quickly- throttle response is bright, no stumble- back to 3000 minimum idle- if I blip the choke lever manually, can get it to 2000 idle- next time you wing throttle, back to 3000- so choke circuit is fine and working- right side carbs do not respond to idle mix screws at 2000, left carbs do- doesn't smell rich- can kill it fast with the choke- checked all the boot screws- boots have never shown cracking and are still flexible- restarts easily with closed throttle warm- sync is good- remember, this all started after long sitting after having this running well- is it a lean condition? after removal 10 times are the boots suspect? can they cause this condition?- Thx

 

Check the temperature of the exhaust pipes to determine whether or not all 4 cylinders are firing. The fact that two of the fuel mixture screws do not respond indicates that those two cylinders are getting little or no fuel.... possible clogged pilots or maybe the fuel screw O-rings might be missing or broken or possibly installed in the wrong position.

 

As previously stated pilot jets are clean, motor is smooth, all cylinders firing- idle mix screws are clean and correct- what about the boots? external air fooling the carbs?

 

I'm out of ideas.

 

Okay So Basically, Your Engine Is Getting Too Much air/ Fuel. At Idle With The Idle Screw All The Way Out, Your Butterflys Valves Are Closed. The Fuel Has To Be Coming From Your Idle Jet, Pilot. Ive Heard Of People Cleaning Jets With ToO Large Of A Poker I.E. Small Screw Driver. If This Is DOne It Can Open Up Your Jets And Cause A Rich Condition. I Had This Same Issue But It Turned Out That My Choke Run Needed Adjusting.
Did You Verify That Your Buterflys Are Indeed Closing? This Can Be Done By Removling The Airbox And Visually Checking. If Your ThrottlE Isnt Adjusted It Can Hold Open your Buterfly Valves. But If Those Butterflys Are Closed, And Your Choke Is Off. Your Engine Shouldn RUnt All. It Needs Air. I WoNder If Something Is In Front Of Your Stop Screw Holding Your Throttle Open. Only Other Possibilities Are Fuel Mix Screw And Float Height.. But Without Air (Idle Screw All The Way Out) And Choke Off (Assuming Its Working Properly) Engine Shouldnt run. Check Your Cables. Id Also Pull Airbox And Your Tank And Hook Up An external Fuel Tank So That You Can Visually See How Slides Are Opening and Butterflys Are Operating. Just Try Simple Things... Its Always Something Simple When No One Can Figure It Out..

 

Could also be slide diaphram holes or poorly installed. Did you clean the main jets and their holder tube side holes ?

This could easily be related to poor carb synch.

 

The Carbs Still Need Air. If I Remember Correctly, The Choke Bypasses Air The The Slide Diaphram And Into The Cylinders. If Your ButterflyS Are Closed Are Can Still Enter The Carbs Through Choke. I Still Feel Like It Could Be Choke Related. If Not That Then Butterflys. One Other Possibility Is That Your Needle Float Valves Are Warn And Even Though The Float Level Is Correct, More Fuel Is Forced Inter The Bowl Causing A Rich ConditioN. Fuel Would Bassically Be Pushed Into The Engine. These Needles Can Go Bad After Sitting For A While. Maybe Pull Carbs, Change Needle Valves, Adjust Float Height, Check Choke.. You Know Basic Stuff. Definently Go Into The Carbs Again. If Your Boots Are Giving You Probs Boil Your Boots And Heat Them With A Heat Gun After. They Stay SOft. Carbs Are Easily Installed By Tilting Front Carb Boots Up. Use A Piece Of Soft Plastic On The Front End Of Ypur Intake Box. Use A Lever Againt This And The Front Cross Bar Over Airbox Thing. Back Carbs Firsy Then Front. Work Boots Be Patient. Chevk Your Sync Screws Too. Contact Billy C For Carb Parts!

 

There are dozens of places to buy carb parts online.

 

This is not quite accurate. The main idle screw only controls the front left carb. The other 3 carbs are connected with linkage. Those 3 can still be slightly open allowing the high idle even with the front left carb completely closed.

 

When I did mine I ended up with a high idle even after VERY careful bench sync. The problem went away after manometer syncing.

http://vfrworld.com/forums/1st-2nd-...f500f-project-update-carb-sync-questions.html

Everybody's mileage varies, though...

 

Bench syncing is wildly inaccurate. It's to just to let you crank the bike and get it running so you can do an actual sync.

 

High idle and hanging rpms are almost always an air leak or a way to lean condition somewhere. I would go back and remove carbs and very very carefully go over everything. I had one i just knew i had done everything right but after going back through them i found two mistakes i had made. One of them was the o-ring in the fuel screw was missing. I forget the other but thats all it took and it was purring like a kitten after.