66cc runs good under load But 4 strokes on No load

My experience with these engines is that maximum torque is produced when the air/fuel ratio is on the rich side of the air/fuel ratio for maximum power.

My experience has also shown that these engines (the 66cc versions) are capable of producing surprisingly good torque (jetted on the rich side) with a standard exhaust system that has had the internal muffler pipe cut off about 2 inches from the base of the end cap.

The extra torque can be used to propel the bike at acceptable speeds using lower rpm, which gives much less vibration and noise, not to mention a much nicer riding experience, than revving the rings out of the engine all the time.
The use of lower rpms (3,200 - 4,200) has a side bonus of making the engine last significantly longer and with greater reliability.
 
My experience with these engines is that maximum torque is produced when the air/fuel ratio is on the rich side of the air/fuel ratio for maximum power.

It's been proven, slightly rich of a stoichiometric (I think that's how its spelled lol) (14.7:1; the air fuel ratio where the engine revs the highest) ratio gives the best overall power. Emissions and fuel economy's a different story tho::D
 
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