Is a Snow Bike hard on the top end?

[Tillbuilt]

I am trying to compare a snow only bike to a dirt only bike. 

 

Can anyone post up a picture of a dirt only piston with 60 hours on it? I am not looking for one that failed. I am looking for a few pics of one that was changed due to maintenance.

 

I did my first top end on my 2015 Yamaha YZ450F and was truly surprised how well the piston looked at 60 hours.

 

 

 

 

 

 

 

[JonL515]

I have a piston from my 14 that was changed at 40 hours I will snap a picture of tonight.  I may reuse it in the future, still looks great.  It was ridden by a 60yr on the track mostly before I bought it.

[c0ncEpT]

Looks great. Measure the piston and the bore. If it hasn't knocked the skirts in or wore the bore I'd put a ring set on it and run it for another 60 hours.

[grayracer513]

This piston is out of my '06 at just over 300 hours of desert racing, a bit of MX, and general rec riding. It really should have been replaced a little sooner, but there was no harm done, and the bore was in very good condition. 

 

The areas of concern to me here were the fact that the wear shows the piston tilting in the bore excessively as indicated by the bright stripe along the bottom of the rear skirt, and the drag marks on the ring lands on the front side (arrows).  The ring lands are never supposed to contact the bore walls at all, so it was past time to switch it out, actually.

 

An often overlooked area when considering the reuse of a piston is the ring grooves.  The grooves tend to wear a little wider at the outside than they do farther in, which lets the ring twist out of square with the bore, affecting wear at the ends of the ring sweep where the rings reverse direction, and sealing in general.  Measure the ring groove clearance carefully with this in mind.

[JonL515]

Here it is.