This has been in other OS .91 threads, but I have one and so does a buddy. Both of ours run great NOW. Get yourself a K&B .61 remore needle valve assemble, $15.95, and replace the OS one. The K&B screws to the firewall or where ever you want it and doesn't leak.

Just for information, I had mine on a Joss Stick, engine out in the breeze. Ran crappy-always leaned out. I normally set it for a smoke trail so I didn't have any dead sticks, but I noticed it leaning out. I finally took it off the Joss in favor of a Magnum 1.08. Good running engine and so is their new .91XLS.

Get the K&B NVA and your engine will work.