Evening all,
I have bought a cbr125rw9 2009 with 20k miles
it's currently having issues with power, every so often it will have a burst of power
Issues I've found so far, low compression (70PSI) should be 195, power issue is worse when warm (so is compression @50psi warm), slow acceleration (if any), max speed is about 40mph
I have so far replaced spark plug, done full service, replaced piston and rings,checked timing(if I've done it right), set valve clearance.

any advice would be grand, been pulling my hair out on this for months 😂

 

Hi MM94,
Welcome to the forum, sorry that you are having problems.
I am not sure that you will get much in the way of specific advice for your machine as most on here have larger capacity bikes, however there is a tremendous amount of general knowledge around.
Taking into account the things that you have already done and assuming the valve clearances are correct, there are probably three things left that could be causing your compression issue.
Poor seal around your spark plug, worn valve seals and / or worn piston liner.
Not sure what else to suggest if it is none of them.
Cheers
Al

 

How was the piston ring gap? Was it within tolerance? Did you hone the cylinder at all?

 

think i made a schoolboy error and didnt check this, i will check this next, what is the next step if its not within tolerance? new cylinder im guessing or resleeve?

 

I don't think it would be worth it. I think they're called Breakers (used parts) over there. I'd think finding a used engine to swap out might be easier and less expensive, but hard to say.

But to answer your question, new cylinder, oversized piston. I can't imagine sleeve's would be available.