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Old 05-18-2007, 02:23 AM   #109
Izzy
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Join Date: Jan 2007
Location: woodbury, mn
Age: 26
Posts: 161
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Default Re: Gas engine tuning for newbies....

Quote: Originally Posted by mfuess
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Izzy,

Sometimes it's extremely difficult to totally eliminate four stroking because of exactly what you describbed. When you eliminate the four stroking and you give it fast throttle it goes momentarily lean.

Try this Izzy,
Fire up your engine & let it warm up. Go back to the throttle position where it "four strokes". Then, begin to completely CLOSE of your highend needle. IF the four stroking goes away, this tells you that your float valve setting is a little too high or your float diaphragm is a little too stiff. IF it does not change the four stroking, you have a leak somewhere...
Your engine should run perfectly on the lowend needle up to about 3000 RPM (give or take a little) with the highend needle totally closed. IF it doesn't... it's time to pull the carb and give it a good clean up.
Hey Mark, I had another try with the DA. is it possible that it may need a carb cleanup even if it's brand new (3 gallons through it)? I set both needles to 1.5 turns, let the engine warm up, and set the HE for peak rpm (about 7000 on a mejzlik 22x8 at 600ft asl). I made sure it didn't lean out and began to throttle down to tweak out the four stroking. The problem still is that when I close the LE enough to remove the fourstroking the engine hesitates when going from full idle to quick full throttle. it doesn't seem to want to quit (on the ground) but you can hear it doubt for a fraction of a second. richening up the LE a bit seems to take care of the problem, or after a flight the bogging is not there anymore. any ideas?
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