92 yamaha low compression What to do?

maximummax · #1 January 31st, 2009, 02:30 PM

hey all,
My 92 3 cyl, yamaha 2 stroke has a compression readings of #1-40 psi, #2-120 psi, #3-120 psi. Obviously I have a proble with #1 cylinder. I do have a clymer manual which I've searched for my next step and it is a little unclear. I'll admint that when it comes to 2 strokes I am a newbie but I have alot of mechanical experience so I don't feel that I will have too much difficulty with rebuilding this power head. I don't want to do more than needed. Should I completely remove the entire power head at this point or should I remove the cylinder head to have a look at the walls/pistons? Does anyone have suggestions regarding best place to buy parts (pistons, seals, etc)? Good experiences or bad with certain companies or brands? Online or not?

Thanks for any and all help

Mike

JB · #2 January 31st, 2009, 04:59 PM

I would first decarb the engine. Though it is unlikely that carbon would cause such a large drop in compression, it is still possible.

If there is not dramatic improvement the next step is to pull the head and inspect the head gasket and cylinder walls. The result of that inspection should dictate the next step.

maximummax · #3 January 31st, 2009, 10:19 PM

Thanks JB. I forgot to mention that I used the yamaha brand stuff (can't remember name). I'll pull the head and go from there. Thanks for your reply.
Mike