86 vf500f engine racing!

I have an 1986 vf500 and it seems to run great but once the engine warms up at highway speeds/rpms the engine races when I pull the clutch in at stop lights and in between shifts. it eventually idles down after a little while but it is extremely annoying not to mention embarrising. Any idea what may be causing this?

 

maybe your rpms r 2..high...or spray some stuff on gas.. cable..it may gave some dirt inside...

 

I have this problem with my bike....not as extream but it's a creeping idle after highway rides.

A carb overhaul and tune made it a bit better but it's still there.

I have 1 cylinder that has bad compression. Hope your issue is somthing less serious

 

Sounds like maybe a vacuum leak? I'd check your carb insulators (boots) to see if they are cracked. You might also consider doing a carb sync - that never hurts. Let us know what you find out!

 

Most idle issues on most vehicles I have worked on came down to vacuum leaks. Intake boots, o-rings, injector seals(not that your bike has those) or otherwise.

 

i have thought about the vacuum leaks before as the cause but never been able to find some thing very diffinitive. i've tried spraying starting fluid around everywhere to see if it was sucking air but nothing really seems to have a problem. The bike only has 18000 original miles and doesn't burn anything and runs great otherwise so I think I could rule out major engine problems.
the boots on the carbs appear to be in ok condition there are no dry rot cracks or anything but I guess there could be some cracks I cant see. how long does it take to replace the boots? I just finished tearing the bike down to the frame and engine this winter and just 2 weeks ago got it back on the road again so I would rather not start tearing everything back apart again but.......also the first 2 or 3 rides a week ago it didn't seem to have the problem so I assumed it to be when I upgraded to an aftermarker exhaust.
when I had the problem last year I attributed it to the fact I didn't have baffles in the mufflers and it was flowing too much air and running lean. possibly causing this reving problem. this was confirmed by a few local mechanics.
the "new" exhaust is a kerker setup and they are basically glasspacks so i assume they flow a significant amount more air then the stock exhuast also.

I was hoping that there was a flood of first gen guys on here with the same problem and new exactly what it was but....!

 

Sounds like a classic lean condition.
If you don't have any intake leaks...
Did you do any re-jetting for the exhaust? Do you have an aftermarket air filter? How many turns out are you running your pilot screws? Does the bike seem to run hot (hotter than normal for a v4)?

 

If no vacuum leak, I would go for a pilot screw set up and carb sync. Your problem sounds evident at around idle and that is what really matters there.

 

You know, I've never gotten that method of checking for leaks to ever work.

Even though your bike has decently low mileage, it's also 25 years old. I'd say if the carb insulators look original then they probably need replaced.