First Gen Idle Troubles

Hey everyone,

I have a 1984 VF500F, came to me not running. After a carb clean up it runs like a top! I was out riding the other and ran into a problem. After riding for 20 minutes or so, when I come up to a stop and engage the clutch the motor idles down so low that it dies! After it dies it really has a tough time restarting. I feel silly sitting a stoplight trying to get the motor restarted, it just turns over and after a fair amount of time it will eventually come back to life.

Other oddities... at freeway speeds I did notice it lurches while cruising, and at times it does rev itself up when the clutch is engaged.

Overall I'm thinking it is something like a vacuum leak but I'm just not sure

I would appreciate your thoughts and/or comments

 

After carb cleaning it runs very poorly.
You need to do it over.

Lurches, speeds up, won't idle

Many issues.

 

Don't despair, Rob. It's the same thing that I was dealing with on my '86 after I did my carb clean. I'd start her up and he idled fine (so I thought), but then after she hit operating temps it would lug down under 800 rpms and clunk out. I adjusted the idle way high and it didn't help. The only thing that would keep her running was to run the choke up about 25%. She'd run with that, but would only idle at about 1800 rpms. It would also make this tapping/popping noise from the lower end, which turned out to be the clutch plates smacking into the basket and the trans vibrating from the cylinders trying to force each other into rhythm. I knew something was up, but couldn't figure it out.

Eventually I pulled the carbs again and redid the idle jets and made an extra effort on the airways. This helped ease the idle up a bit, but it still stalled and had low power on take off. Pulling the carbs the 4th time I noticed that the springs on the sync screws were looses and one of them was missing. Went to the hardware store and picked up a 6 pack of springs that closely matched, trimmed off the excess length and replaced the springs. Did a bench sync and it runs perfectly now.

"Other oddities... at freeway speeds I did notice it lurches while cruising, and at times it does rev itself up when the clutch is engaged."

The lurching is caused by the fuel not burning properly from the carbs sending different amounts of fuel into the intakes at the current throttle position. Eventually the fuel level hits a point in the mix that it'll catch and you'll get a short burst of power followed by a low level of fuel and the cycle will repeat, usually every 30-45 seconds depending on the amount the carbs are out of sync. Same thing at idle with the clutch in, the fuel level builds and the idles increases for a short time then drops down again.

My advice: Recheck your slow circuit, pull and inspect your idle jets. Clean the filters in the float bowl, and make sure that all of your airways are clear inside of the carb. Check the rates on your springs underneath the carb at the sync screws and replace if necessary. Then do a bench sync and reinstall. Check your idle and throttle response, and if possible do a full vacuum carb sync and test your emission numbers to make sure you've got it dialed in right. You should notice a considerable difference once you do the bench sync.

 

Lazy,

Your help was sooooo apreciated! I can't begin to tell you how much it helped out. I went through and re-cleaned the carbs. Come to find out, the idle jets were plugged again. So I really did a thorough job soaking in cleaner tub from napa and some gentle work with a guitar string. It looked a ton better when finished. I also went in and gained access to the both sets of adjusting screws (sync and fuel air mixture). Once it was primed and ready to roll the machine sounded sweet!

After taking it out for a test ride I was really pleased with the way it handled and how much better it performed.

Thank you for your advice and help.

 

Glad I could help, Rob. Enjoy the ride!