2018 xc250

[Tommyz662]

I have a used bike I?ve been riding for 2 seasons. Not sure on the hours of Topend. Comp was at 150psi Cold. Seems a bit low to me. What are you all getting for a healthy topend? I will err on the side of caution for fork over the $200 for a piston etc. Just curious here

 

[Jacob 'Berg]

I have a used bike I?ve been riding for 2 seasons. Not sure on the hours of Topend. Comp was at 150psi Cold. Seems a bit low to me. What are you all getting for a healthy topend? I will air on the side of caution for fork over the $200 for a piston etc. Just curious here

Yes, compression should be higher. Regardless of current compression, the top end should be replaced if you are unsure of running hours and have two seasons or riding on a used bike with unknown hours on the piston and rings.

Take a compression reading with the fresh top end so you have a reference point, future compression tests will tell you when you are at the lower limit due to wear. About 170 psi.

I have the same bike and replace the piston every 90 hours or so. Piston and rings have enough wear to warrant replacement, but not so worn that I am concerned with piston rocking in the bore or skirt failure.

 

[Jacob 'Berg]

Invest in an hour meter if you do not have one.

 

[webmaster]

You might want to check this out..

http://www.gasgasrider.org/html/measuring_squish.html

jeff

 

[Tommyz662]

Thanks very much gents. Any recommendations on pistons? I?m going to have a machinist friend of mine take care of the squish.

 

[Jacob 'Berg]

Thanks very much gents. Any recommendations on pistons? I?m going to have a machinist friend of mine take care of the squish.

I like to run vertex (or S3), which is a cast piston. Wossner if you prefer to use a forged piston.