So here's the situation... he runs the bike and if he gets it over about 4k RPM, it tends to stick there... RPMS don't drop back down. So we pull the carbs, spray 'em down and out with Gunk Carb Medic and make sure that the diaphragms are alright. Cleaned the slides, made sure the jets were clear, yada yoda yada. The slides seem to be a little on the sticky side... they don't drop back down easily. A little better now that we've cleaned 'em but still a little sticky... figured that they'd do better once we get some gasoline flowing to lubricate them a bit.
Put 'em back in and can't get the bike to run sans choke. Finally get 'er running without the choke but not at idle speed... has to be at least 3k RPM.
So we pulled the carbs again, checked the low-speed circuits for blockages (they all seem clear), sprayed it some more for good measure... scrubbed with q-tips...etc. Put 'er back in and we can get it to run without the choke, finally, but now we're back to the high-RPM problem unless we snap the throttle open and closed.
Irritating. What am I missing?
All of the vacuum ports are plugged (two with screws for synching, one was never drilled, and one goes to the petcock) so I don't think that it's got to do with a vacuum leak (which would be my first thought)... sprayed the boots with WD-40 to test for leaks there.... no joy.
I DID notice, when we had the airbox disconnected, that if I covered the air intakes of the carb on the right side, and then uncovered them, we'd get a high-RPM spurt for about 10 seconds, but if I covered the air intake on the left side, the bike would just die.
Both float bowls have fuel going into them (they are cool to the touch)...
Plan is to pull the carbs, separate them (only if needed) and dip them on Saturday, but I'd like to see if anyone's got some good suggestions that I could take with me... Especially if someone knows of some problem with this specific bike that would manifest in this manner...
Thanks for any ideas..