2007 Yamaha Yz 125 Piston,Ring, Cylinder and Cylinder head Pictures

I have some more pictures of the cylinder on mynew to me yz 125 that i recently purchased. Me and my brother took it apart about a week ago and it is scratched up pretty bad and i am trying to find out how to replace it and the cheapest but best quality fix. I took it to my local dealer and the mechanic said they can send it away to montreal(Quebec) and get it pressed out and put a new sleeve in the cylinder walls for 299 and then id have to buy the piston and rings and gaskets etc... I was looking for some opinions on this option and also looking for any other option that might be cheaper, more efficient, or just more of a reliable option. Also i want opinons on the cylinder walls, they are pretty scratched up up front and the dealer said it looks like it was from over heating and maybe not getting enough gas or the coolant wasnt mixed right. i took the coolant out and it was just like water so i figure that may be the reason why its tore out. Anyways here are some pics. Tell me what you think?

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its toasttt, holy that bike has seen better days.

Simple cheapest route,

get the cylinder replated and honed to fit a new piston, its amazing what they can fix. The sleeves work but they aren't as good as a cylinder with plating.

new piston (pro x, vertex, oem) i liked forged pistons like wossner, wiseco but they cost more. namura is shit, dont use another one.

I used to used to use mongoose machine in vancouver for all my stuff. but find a place that can replate it, send it to them with a new piston, they will repair and replate the cylinder and hone it to perfect clearance for the piston you bought. If the cylinder is scrap and cant be saved, then turn to getting it sleeved.

If you go with oem, pro x, get the smallest piston, they sell them in slightly different sizes to match the cylinder as it wears and gets bigger. start with smallest piston so you have room to grow.

i just bought the bike and from what i can tell it was mistreated and not maintained.... i intend to fix that but thanks ill check it out.

Definitely in need of a replate. I am by no means an expert, but I would say that wear was caused by dirty air. Maybe an un-oiled air filter, or incorrectly installed air filter allowing dirt and sand in. It's just a thought... check your air boot and filter for leaks.

Also, I used Millennium technologies here in the US for a replate... not sure where to go north of the border for that though. I'm sure someone will be along with more info on that.

Edited by JFielder23

I think CvTech in Montreal does it as well. Maybe someone here can confirm.

I dont know for cvtech montreal but 3 years ago i sent my cr250 cylinder to les ateliers adrien bernard or cvtech-aab at thetford-mine, quebec. I guess it the same. So yes they do it and they give a really good service. Give them a call and yes they speak english.


That cylinder is missing a section of plating. That is gonna be from excessive hours, lack if maintenance- running old pistons too long causing too much piston to cylinder clearance and weAring off the nikasil coating.

Also has a lot of scoring on that piston, it's one of those cheap ass namura eBay pistons. Complete junk. I wouldn't use for free. I'd be pissed at the seller he sold u a pile of shit. How much did h pay for the bike? I'd give those old parts back to the seller.

U need a new cylinder or new plating. I use eric gorr millennium technology for years and always had great work, never one problem

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