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Old 08-02-2011, 08:00 PM
Dymaxion Dymaxion is offline
Motorized Bicycle Senior Member
Join Date: Jan 2010
Location: Michigan
Posts: 67
Default Time to tune - need help.

I recently rebuilt the top end of my HT engine (new cylinder, piston and rings). I have probably 50 - 70 miles on it since rebuild and it is really running in well - much smoother and pulls stronger now. So now it is time to tune it up a bit.

Here is where we are at:
-motor is a 66cc gt-5
-broken it on opti-2 at 72:1
-all else is stock
-stock jet and needle all the way down (clip at top notch)
-idles great
-4strokes at mid-throttle almost all times unless under high load (such as steep incline)
-wot runs really smooth but will 4 stroke at times
-plugs look good to slightly rich at mid throttle and wot

So I am thinking it is time to step down to a smaller jet and raise the needle a few notches. I ordered the .68mm and .66mm sized jets from SBP and they should arrive in the next day or two.

Do you think I am on the right track?

Last edited by Dymaxion; 08-02-2011 at 08:04 PM.
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