Ibautoman:

With a Saito FA-65you could have either one of two carbs. The older engines came with an air bleed type, the later ones have a two needle type.

If you have the air bleed type, be very sure your throttle linkage does not pull the lever away from the carb. There is a flow regulator valve inside, the throttle barrel is the moving part and it has to be firm against the inside end of the bore. Also check the small wire spring clip on the lever end, you should see its two arms pressing the barrel in. If the barrel is not kept tight you will have good top end, but many problems trying to slow the engine. You will have the same result if the linkage pulls out on the lever.

If yours is the later two needle carb you probably have the low speed adjustment set too lean. The LS adjustment has a strong effect up to about 3/4 throttle. When everything else is fine, tank height, no leaks, good fuel and plug, etc, most Saito running problems are a lean adjustment on the LS. The engine will run fine with it rich, but lean can be a real pain.

Hope this helps.

Bill.