Good luck, I have had one of these for a couple of years and I am still fighting the same problem. I have tried every needle configuration. I can get it to run well with the cowl off and then when I install it and fly, it all changes. I have just ordered the carb plate so I can vent the carb diaphram into the fuse. Hopefully that will keep it more consistent with or without the cowl on. In general the motor runs good enough, but I am not sure I would purchase another BME motor. This has been too much screwing around and I lost faith in the company with the 3 or 4 years I waited on lists for the never going to happen 55. I hear the 115 is better, but once bitten twice shy.