I’m having issues with my Alpha 40 trainer. I have had the plane for about 3 months, and flown 20 –25 times. I am now having issues with ‘surging’. When I get my throttle from about ½ way to full throttle, the engine is very slow to get to full RPMs. Sometimes it is totally unresponsive from ½ throttle to full throttle, staying at the same RPMs or VERY slowing winding up. We can see some bubbles in the fuel line from the needle valve to the carb. At full throttle especially. The engine is also surging lower then higher at full throttle as well. We have made it richer and leaner as much as possible, and it has not resolved the issue .

Based upon several suggestions, I dismantled the card and the needle valve (did not remove the jets), and flushed it with Isop. alcohol. Hopefully this would remove any gunk clogging the jets. I lubed it up again with a little 3 –in- 1 oil, and reassembled. I tested again, and I am still having the same issue at full throttle, and it is slow to rev up to full RPMs.

Any suggestions… New needle valve?