2002 xc125 trouble
 

Hey guys I haven?t been on in a while being wide open coaching ball. I am hoping you guys can help me out. Last weekend we went on a pretty good ride. Bike ran great until we were almost back to truck. Kinda choked out and went to crank and had very little compression. Figured I may have broke a ring so I pushed it back to trailer. Tore into it this weekend and found the left side power valve broken and it did break a ring. That brings me to this..... the cheapest place I can find a valve is $110. The cylinder wall looks fine and mics out to about 53.85mm so I don?t think it?s ever been touched. The piston looks very good except for one tiny place in the top edge. So I have a few questions.
1. You guys have any better advice on fixing the valve. Cheaper??
2. You guys think I need to change piston. ?
3. Last big question is when I left it last night with head off apparently the coolant hose slipped down from where I had it pinched off and filled the crank and rod cavity full of coolant. How do I drain this? Please don?t tell me I have to split the case :confused::confused:
Any help or info will be greatly appreciated

I don't know about the 125, but on my 200, and 250, 300cc there is a drain plug in the bottom of the crankcases. Comes in handy when you need to drain the motor after filling it with water for various reasons.
Look for a hexagon head (17mm?) at the underside of the crankcases.

You can use yz125 power valves in the (non-TM) GG 125 engines. I think there were at least two different versions with different diameter top slide shafts so you need to verify you get the ones that cross over. The Yamihaha versions are a little cheaper new or you can find some good used ones on ebay if your budget so requires.

These pistons are the same as YZ125 pistons which are cheap so I would replace it. I would flush the crank and bottom end bearings with WD40 a couple times and blow it out with compressed air. I would then pour some extra premix oil into the crank area including down the oiling holes in the cases.

That sounds promising! I am not sure what you mean by non-tm though. Do i just mic the shaft to find out size?

The very early Gasgas bikes used TM engines.

How about these?

I am not sure if those Athena valves will work for a stock cylinder.

They fit like a glove

Great News!!! Are they aluminum or steel?

Aluminum. Using The yz cross reference i will have a a new top end, power valves with new springs and gaskets for around $200