first look at the top end on my 125 sx 05

I got this bike in April And the guy said he had a new top end on it so since then ive been riding it thinking it would blow up or the top end was bad... so today i took the top end apart the cylinder Looks great the piston looks good it has two rings on it.. but before i did this i ordered rings thinking it was a single ringed piston now i just got to wait in tell the other ring comes in

But the bottom end has noo up and down play soo i wont have any bad thoughts about the bike :-)

Well, all of that information could have been answered with a simple compression test. These bikes are very easy to do that with and if the compression is good, you can keep riding it. Generally speaking, the rings go bad way before the piston shows any sign of serious wear, if the jetting is OK.

Though I'm a piston replacer, I don't even think about just replacing rings. The modern pistons have coatings on the sleeves which help prevent cylinder wear. Those coatings wear off in roughly 40 - 60hrs and by then, you'll need rings anyway. So I tend to replace the whole piston instead of just the rings, which actually does help with cylinder wear. Since ya gotta replace the gaskets when you do a top end anyway, the added cost of a new piston isn't so ridiculous.

Edited by tye1138

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