ORIGINAL: brunofporto
This already happened when the engine was new. The needle does not feel "loose" or anithing. It does not have any (external) signs of damage. But when I hold the needle at high RPM it is possible to feel the engine leaning (right word?) and becoming more "smoth".
I removed the needle extension to reduce the vibration on that component and it is possible to feel the difference.I fear that this small gap between the parts can damage the needle with time.
The engine have 10hrs (more or less) of use now, based on the ammount of fuel already used and TX timer
I'll check it again this weekend and try to record this behavior in video.
Thank you for the help!<br type="_moz" />
There is one of two things happening here.
1) the small amount of play between the threads of the needle valve is allowing you to push the needle itself agaist the side of the seat, closing off some fuel and leaning the engine, or -
2)when you push the needle to the side there is a small air leak getting past the o-ring which will effectively lean out the engine by adding more air to the mixture.
To determine what is going on take a small piece of silicone tubing (about 6mm long) and push it over the needle valve so that it forms a seal around the needle valve and the needle valve holder. If the engine still changes when you push against the needle valve then it is simply a matter of the needle being pushed against the side of the needle seat and there is no issue that needs to be resolved and you can probably turn in the needle another click or two because the engine wants to run a bit leaner anyway. If the change does not occur then this is an indication that you are getting air leakage past the o-ring and you should change out the o-ring, or just leave the silicone seal in place and continue to have fun with your engine.
Pete