Hello, can someone advice on the frequency of piston change of a 125 sherco ST please. It’s a 2012 and compression seems fine, should I stick one in while bike is stripped down or would it be ok

thanks

s

I had a 2014 125.  After about 2 years of riding every weekend in competitions and the occasional practice for an hour or so, the top end was a bit rattly, although it still went well.  The bore looked fine and the piston skirt had a bit of rubbing/scuffing.  I was advised to change the piston, piston rings. wrist pin and little end bearing.  After dismantling it I discovered that the little end bearing was obviously very loose.  The wrist pin had wear that you couldn't see but you could feel.  Apparently the wrist pin hole through the piston becomes slightly elongated after hundreds of hours of use.  This wear leaves a slight gap, which produces more rattle as the bits wear and the gaps grow.  When I assembled the new bits and compared them to the old, the wear was very apparent. 

The new piston and associated bits made the motor much less rattly.   

I bought the bits online from Splatshop.

PS: I used the same sized piston and the bore was unmarked, with no ridges.

 

Edited April 1, 20206 yr by stpauls

Great thanks for the info I think I may aswell order one and stick it in altogether while the bike is stripped down.

Have you measured the cylinder bore and checked its condition?