Chris

On mine, which acted the same way, I simply flattened one pipe with a pair of pliers until it was aprox. 75% closed. At this "setting", the engine ran well and the needle valve worked as it should. I find that this engine likes to be run pretty rich, BTW.

After probably 20 or so flights, I opened the squeezed exhaust pipe a little (to about 50%), and found that I could still adjust the needle valve and the engine made a little more power. I have not done any further experimenting because I am happy with the way it runs now.

Interestingly, when I emailed Bisson about this idea of smashing a pipe, their tech guy said he saw no problem with it! Makes you wonder if they actually test run an engine when they make a pipe for it.

Sandy T