Hi:

I have a YS91 engine in a Fly Baby that I just completed. The engine is 2
1/2 years old and it ran for the first time last weekend. It runs great
with a smooth idle and great acceleration. By the way this is the
supercharged version using a pressurized tank. I have the check valve that
came with the engine in the fuel line as per the YS diagram.

Here is my problem, when I slow it down with the throttle complexly closed
it keeps running. I even removed the throttle stop screw so that the
butterfly valve can close completely. It runs so slow it is actually
beautiful to see. It just ticks away very smooth at an extremely slow rpm.
But it will run all day like that. The only way I can get it to shut off is
to pinch the fuel line. That is not a good option though because it will
be hidden when the cowl is on and it is too powerful to put some friction
the small hub to stop it.

The prop I am using is a 16 x 8 zinger.
I am using 15% nitro mix with synthetic lub.
I still have it quite rich for to break in.

This is my first YS and I am suspecting that there is something wrong with
the carb. Maybe an air leak past the throttle valve but I am hoping I am
doing something wrong. Any suggestions?

Best regards
Lou