Loss of power when engine hot...

It's easy to try a new plug.
It doesn't make sense that pulling a little extra weight would make it perform differently than with just you on the bike.

It would seem that a slightly richer mixture would help IF you were on the edge of being too lean, but since you said it didn't, I'd check the air filter, and go with a new plug.

borntofli said:

Ideas????

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How about going on a diet? Seriously, how much do you weigh, the bike weigh, the trailer weigh, engine, etc. and then your pulling an additional 50 - 100 lbs.

To me that is a lot of weight for a little 66cc engine; especially, if you are not peddling.

Solution: Either buy a bigger engine or lose some weight.

Chris
AKA: BigBlue

borntofli said:

Ht 66.... Under normal riding bike seems to run fine.... When I am pulling my trailer, (50-100 lbs of load) after it warms up fully it bogs when accellerating w/o pedal assist...

Ive tried enrichening the mixture to provide more coolong but no help.... When you open the throttle to accelerate it sounds very loud (not exhaust loud or engine noise, Not like the normal high pitch ring ding ding but a low sound and decellerates)..

Could this be a loss of compression causing this? I guess I can take the exhaust off and look for blow by on the piston...

Ideas????

Could it be as simple as poor performing plug? (bp6hs)

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Hi. I think your engine is experiencing detonation when it gets hot. When detonation is occurring, the engine will sound louder. When this is happening, little of the energy can do work to the wheel, which is the power loss you are experiencing. Also, this abrupt expansion of detonation will cause engine temperatures to rise considerably. Detonation is very common with these engines when they are using the stock cylinder head which has a poor combustion chamber design and minimal cooling fins. A "hot" spark plug with extended electrodes can also start glowing red hot, causing pre-ignition which can also cause the engine to sound a little louder. Both these problems can quickly cause severe engine damage! I have broken cranks and melted holes in pistons from these problems.
-Fred