Please look at my piston...replace?

[Fultoncm]

I did a top-end rebuild and everything was going fine until it stalled. I opened it back up to find the power/exhaust valve had seized and the arm broke off of it. You know what happens next...the piston smacked it a few times. Luckily, I think I might be able to get away with only replacing the valve. Check out this picture of the piston and tell me if you think I should replace it (click to enlarge, I circled the worn spot)?? I hope not, cause I only have about 30 minutes of riding on that biotch. I also did a compression test and it holds 60 lbs. I can't find any benchmark for this, so does that sound good?

<a href="http://img21.imagevenue.com/img.php?loc=loc299&image=73103_CIMG0030.JPG" target=_blank><img src="http://img21.imagevenue.com/loc299/th_73103_CIMG0030.JPG" border="0" alt="image hosting by imagevenue.com"></a>

 

[robwbright]

60 lbs? From what I understand, you should be AT LEAST 150 lbs.

 

[Fultoncm]

Oh ****, well, I guess I will need a new piston.

I should be able to replace one exhaust valve right? It's not a "replace both" type deal is it? One of these damn things is $90.

 

[warlockboy]

I think you should just to be safe

 

[darringer]

You should be able to get the single exhaust valve separately. The piston is shot. Definitely replace the piston AND rings. If you run THAT piston/rings, you'll be even quicker tearing it down after the next 30 minutes. If remember correctly, my 99 RM125 (same motor) consistently would run 190-195psi @ sea level.

 

[sick 96 250]

def replace any parts that your not sure about. I dont think PSi should be up near 190-200 on a 125, more around 160-175 i believe. You can get a whole piston and ring kit of the famous auction site for very cheap if you need to and that would also prob be your best bet for the powervalve you need as well. Good Luck

 

[Fultoncm]

Thanks for your guys advice. I found a $60 wiseco piston kit at Midwest Action Cycle, and all the gaskets and exhaust valve at Ron Ayers for $111. I decided to get two crank seals while I'm at it. I think those were going anyway. I've had quite a bit of smoke already and it might help with the compression. I'm thinking my compression was low because of the piston. I was just out checking out the ring and it was stuck in that worn spot. Probably loosing compression there.

Damn these motorcycles!

 

[Badgadjit1]

ya, when i hear of ppl wanting to get dirt bikes..i just tell them to go sit on your from porch witha a bucket of money and just start burning it heh..instead of getting a bike..lol