My TT91FS hesitates if I goose the engine, but transitions fine if I gradually advance it. I'm assuming the low end needs some adjusting? Now, would I need to richen it or lean it?

Also, on a second TT91FS I have after removing the glow driver the engine runs fine at 1/4 throttle on up. If I reduce the throttle to idle, it idles fine for about 30 seconds then dies off. Would this be too lean or too rich on the low end?

One more, am I correct when I say the fuel tank center line needs to be equal to the high end needle height?

thanks

If on throttle up the engine hesitates, puffs a cloud of smoke, then spools up, you're rich. If it hesistates on throttle up, with no big cloud of smoke, you're probably lean.

On the second engine, if it begins to speed up at idle then dies, it's lean. If it just slows down then coughs and dies, it is probably rich.

If I remember correctly, according to Clarence Lee, the high speed needle valve should be about 3/8" below the top of the tank. Half-way is too low.

On either of those engines, go to low throttle, then, pinch the fuel line right before it enters the needle valve. If the engine increases dramatically in revs before it dies, it is rich. If it just sort of dies, it is lean.

It SHOULD slightly increase in revs when it is right.

Another test is this: If you start the engine at idle, and there is a noticable decrease in RPM when you remove the glow plug, it could be rich.