I completely rebuilt my 1991 CRM including the engine 2 years ago.
Every bearing and seal in the engine was replaced. The piston, rod & crank were all checked and were well within usable limits and so were reused. A new small end bush and piston rings were fitted. The barrel was fine and within spec and reused.
My problem now is that if I am in too higher gear and the engine is bogging down, when I open the throttle, it sounds like there is a 'wood pecker' in the engine until the power pulls the engine speed up to match the gearing.
This sound 'seems' to be getting worse although the engine is running and performing fantastic.
Is this just a fuelling issue or do you think it a large or small end bearing problem?
Before I go to the extent of pulling off the barrel I thought I just ask.
Thanks for any advice,
118118 - Stu

IMO, your engine may making to much compression, which can be caused by, excessive carbon, unlikely given the history, or a jammed ring, or p/valve.
Have you tested the compression, if not it may be worth doing.
Your not running with old fuel in there are you by any chance?
What do others think?
Mike

It is perfectly normal for an engine to 'complain' when it is asked (too much throttle) to do much more than it is capable of giving at too low revs. 2 strokes particularly complain.

What gearing are you on Have you recently made the gearing taller

i would agree with knackered.

fit a larger rear sprocket and use a lower gear!

if the engine "labours" at low rpm the gears between the crank, clutch and balancer will rattle with each power stroke.

Also the clutch torsional damper will be oscilating, gearbox backlash will be doing the same, chain snaching etc.

Im not saying your engine couldnt be faulty, but if it doesnt rattle when the rpm is higher i wouldnt worry to much. (yet)

Thanks for the advice guys, its put my mine at rest for a while. I'll see how it performs on the next trail ride.