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Dallin

YZ125 2001 yz125 low almost no compression

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just recently put a new wesco pison kit in my bike and now it doesnt want to start,  was running just fine about 8 days ago and feels like it has barely any compression. cylinder walls have no scaring and the old piston was clean as well. after putting the new pison in and put the cylinder and cylinder head back on I kranked the kick starter a few times to make sure nothing was seized up or fell "chunky". didnt mess with anything else when doing to top end. any ideas?????

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3 hours ago, YZDOC said:

What was your procedure of installing the new piston?

Did you just toss a new one in, or follow the manual?

6 hours ago, Sullysully said:

When you say it was running fine, is that before or after putting in the new piston?

I followed the manual on everything and it was running fine with the old piston in it but even then it felt like it had low compression but only took about 3 kicks to start 

 

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1 hour ago, john stu said:

You're supposed to also install rings when you install the piston

Maybe if you're racing the bike you do.

If you're trail riding you don't even need rings if you use Rotella.

  • Haha 2

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Just now, beezer said:

Maybe if you're racing the bike you do.

If you're trail riding you don't even need rings if you use Rotella.

I don't race just trail ride and yeah I put the ring on it 

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5 hours ago, Dallin said:

I followed the manual on everything and it was running fine with the old piston in it but even then it felt like it had low compression but only took about 3 kicks to start 

 

 

37 minutes ago, Dahomie Cov said:

Did you check your ring end gap or the actual diamameter of the cylinder? Also most manufactures will have different piston sizes for instance my 2002 yz125 have a piston that's coded C. Did you get the right size piston? 

He answered that here when I asked him. \/

 

9 hours ago, YZDOC said:

What was your procedure of installing the new piston?

Did you just toss a new one in, or follow the manual?

 

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