Motorcycle Repair: poor idle, yamaha 750, air leak

Question
Hello, I have a 1982 Yamaha 750 Maxim with 8000 miles.This machine will not idle. High speed is good. I have had the carburetors off several times, everything is clean.Fuel level is proper.
Using the choke I can regulate the idle speed,however it is impossible to choke this machine enough to kill it- just revs up.There is a pilot screw that has little effect. I have searched for an air leak but the carb mounts are ok the pulse line is good.Thanks for your time.Bill

Answer
Hi Bill.
 You could still have leaking manifolds.  They don't have to be loose or improperly fitted to leak.  If the manifolds have any cracks in them, they are leaking.  There is no repair for that, if it is the case.  If they are bad, they need to be replaced.

 The test for it is to run the bike and spray something like ether at the manifolds from both sides.  Do each manifold one at a time.  If the revs come up, then the manifolds are leaking.

 Remember that the bike is 22 years old, so even if it has been garage kept all of that time, there is still the possibility of dry rot in the rubber.

Let me know what you find.
Good luck.
FALCON