86 VF500F Idle issues

I'm looking for some help with an idle issue. My 86 VF500F sometimes idles right (about 1300 rpm) but when you ride it, the idle changes to about 4000 rpm. If I stop, put it in first gear, and "lug" then engine a bit then the idle will drop back to about 1300 and seems to stay there. It doesn't seem to matter if the choke is on or not. Other than that it runs fine.

I've just finished cleaning the carbs and checking the valve clearance. The carbs weren't really dirty and I had the problem even before taking them apart. I did find that one of the slide rubber pieces on one carb had a small whole and that someone had tried a repair but the repair was peeling off. I tried another repair (shoe-goo seemed to do the trick).

I've called a few local repair shops to ask about synching the carbs, but they all say thats probably not the problem and they want to tear the carbs apart again. They've told me that synching the carbs never does much good (even the local Honda dealer said that.)

I don't have a carb synchronizer, but if its the problem I'd be happy to get one and give it a shot.

Any thoughts? A carb synch? Or pilot screw adjustment? Or do I need to do something different with that slide repair job?

Thanks!

[image: View Post]flwoolybugger, on 01 October 2010 - 08:20 AM, said:

I'm looking for some help with an idle issue. My 86 VF500F sometimes idles right (about 1300 rpm) but when you ride it, the idle changes to about 4000 rpm. If I stop, put it in first gear, and "lug" then engine a bit then the idle will drop back to about 1300 and seems to stay there. It doesn't seem to matter if the choke is on or not. Other than that it runs fine.

I've just finished cleaning the carbs and checking the valve clearance. The carbs weren't really dirty and I had the problem even before taking them apart. I did find that one of the slide rubber pieces on one carb had a small whole and that someone had tried a repair but the repair was peeling off. I tried another repair (shoe-goo seemed to do the trick).

I've called a few local repair shops to ask about synching the carbs, but they all say thats probably not the problem and they want to tear the carbs apart again. They've told me that synching the carbs never does much good (even the local Honda dealer said that.)

I don't have a carb synchronizer, but if its the problem I'd be happy to get one and give it a shot.

Any thoughts? A carb synch? Or pilot screw adjustment? Or do I need to do something different with that slide repair job?

Thanks!

It sounds like your high idle is due to your choke/enrichment circuit being stuck open. When you cleaned the carbs did you just do the bowls, or did you do the chokes also? They are prone to gumming up such that they will stick open even though you slide the choke lever back on the handlebar. Lubricate the brass rods and all the linkages also after you douch out the plungers. i'll bet you have brown spoogy gum or varnish around the plungers holding one or more open all the time.

But then again if the pilot screws have been screwed around with to compensate for poor idle, then you may have two issues to deal with. The idle screw may be backed way out because the pilots jets are clogged. Did you run a 0.013" metal rod (e.g. #80 drill bit) thru the pilots to make sure they were clean? That is a tiny-assed orifice that clogs easily and is hard to unclog without rodding it--chemicals won't budge that sludge. Did you clean the air jets? Make sure the gas jet and the air jet of the pilot circuit is clean and flowing freely or you will be chasing your tail for a long time.

A (w)hole in the rubber diaphragm of the carb slide is a big deal when you get the idle fixed you will need to run off the needle at higher rpms and throttle openings. That needs to be fixed with rubber cement if the hole is small, or replace the slide/rubber if the hole is too big to patch. But rubber cement can patch some mighty big holes if you layer it up around the edges and let it dry, then close the gap with another layer.