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Old Dec 30, 2012, 06:56 AM
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Originally Posted by kenh3497 View Post
I believe you have answered your own question.....

The tank is to high causing some minor flooding issues at low speed. I would suggest leaning the low speed mix 1/8 turn and see what happens.

If it were me I would screw the LS needle in and count how many turns it takes to LIGHTLY seat the needle. Now back it out where it was. THIS IS YOUR REFERENCE POINT. If you mess up badly, lightly seat the needle and back it out to your reference point and start again. Same for the high speed needle.

Once you have everything set so the engine runs well, turn the needles in counting the turns and these are now your NEW reference points for a good running engine.

Tuning an engine is not rocket science, and there is no black magic involved. Just pay attention to what you are doing and take a note or two to remind you what you have done. Good luck with your engine.


I had one of these on a .40 size GP CUB and it was awsome power. Mine was inverted as well and I too had a difficult time tuneing it. One thing that I did was just like the above post. Only make vary slight adjustments nothing drastric. Give it a few seconds between adjustments so the the fuel can have time to adapt to its new flow.

One more thing. Make sure that in its new home there is plenty of clearance for the carb hole, 1/2 inch is minimum but 3/4 works real good. Sometime turbulant air through the cowl can do werd things to a gas engine.

Last, You may want to lean your gas to oil ratio a bit. That also helped mine out. I used 30:1 in mne instead of the 24:1 recommended.
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