86 XV700 Idle Problem

[N3Bruce]

I've been helping a friend get his low-mileage 1986 XV-700 back on the road after being stored for over 10 years. We found a lot of thick sludge in the gas tank and the the rest of the fuel system. We had to resort to putting the fuel tank into a tumbler and filled it with nuts and bolts and laquer thinner to remove the sludge inside, and I've disassembled and cleaned the carburetors, and replaced some of the vacuum lines and so on.

I've gotten the bike to the point that it will run, but especially once it is warmed up, the engine has a tendency to race, i.e. it won't drop down to a slow idle quickly, or it will just sort of run along at about 3500 RPMs or so..I don't see anything obvious, such as a disconnected or broken vacuum line. I've had the carbs off twice, the first time when I did the original cleaning, the second time to clean the choke circuit, which I overlooked the first time. Both times I checked the diaphragms for tears, pinholes, etc, and made sure the sliders moved freely in the bore. We've put a few hundred miles on the bike since I've had the carbs apart, but the problem seems to be getting worse.

The only thing I can think of short of pulling the carbs again is the mix control valve, which is on the left side of the engine, and lists for $110 at PowersportsPro. Pulling the carbs again is a real pain, so is paying over $100 for a part we may or may not need, so I'd like to guess right before I commit myself either way. The Haynes manual we have is of little help with this regard either.