S90 over reving

ive put new o rings both ends of intake manifold , new gasket on carb side. Sanded surfaces flat on glass & 1000 grit paper. Bike starts right up , gets to idle & any lift of cable bike revs up & takes forever to drop back down, even though the slide snaps right back !!! Totally confused & frustrated at this point. Any ideas that could cause this greatly appreciated. Thanks, Tom

One possibility...and this is a bit of a longshot...the carb body or/and slide are worn to a point where you're getting "false air". Only way to definitively rule this out would be testing with another, known, carburetor, probably not he easiest thing to do with this model. And a new carb is kinda pricey just to use as a testing device...especially when it may not be the problem. As an interim test, remove the air filter, then rev the engine, close the throttle, then cover the carb inlet with you hand. The revs should plummet, almost instantaneously. If the revs still trail-off gradually, then there's an air/vacuum leak somewhere in the system.

Another possibility is air leakage at the carb cap, above the slide. That's easy enough to check. Temporarily seal the the cap to the carb body using electrical tape; the same can be done to seal the throttle cable from the brass ferrule right up to the outer cable housing.

Tom, I thought you had this solved.

I think it's fixed as of last Sunday. Problem is, different posts talking about the same issue.

Okay, that clears it up. Nothing like multiple threads on the same problem.

Couldn't agree more. if racerx views this, the bike was lean and a needle clip adjustment solved the issue.