2012 wr300 new top end?

Had some blow by and burnt off the coolant 3 laps in for the day. noticed there was a problem when i started losing power so i pulled off the track and my bike shut down. It didnt seize but it lost all compression. i rolled it back. later I pulled the head and the cylinder and piston look fine but noticed it did burn off most of the coolant so it overheated which caused the thing to be in the state its in. Im wondering if I can get away with a new piston, rings and milled head or will i have to replace the entire cylinder? Any ideas on what to do from the husky fans would be appreciated.

Edited by eggimal

What is the shape of your cylinder? Had similar issue with my WR 250 after the oring on the head lead pressure to the cooling system. In may case i had no scars on the cylinder walls so i just fitted a new piston/rings and had no similar problems after that.

You can't just "mill" the head on a 300. Someone who knows what they are doing can do it for you though. He is on vacation right now, but knows his stuff http://www.rb-designs.com/. What does the piston look like? If it looks find just throw some rings in it. Heck, you might be able to put it back together without replacing any hard parts. Just find the coolant leak.

Edited by EagleFreek

Had some blow by and burnt off the coolant 3 laps in for the day. noticed there was a problem when i started losing power so i pulled off the track and my bike shut down. It didnt seize but it lost all compression. i rolled it back. later I pulled the head and the cylinder and piston look fine but noticed it did burn off most of the coolant so it overheated which caused the thing to be in the state its in. Im wondering if I can get away with a new piston, rings and milled head or will i have to replace the entire cylinder? Any ideas on what to do from the husky fans would be appreciated.

 

 

did everthing still seem torqued down when you stripped the top end..??,

 

 

only obvious routed for loss are ,

 

#1 =  Head seal O-ring

 

#2 = through jacket / base gasket,

 

 other porous type issue  -  into exhaust port and steamed away  ?( you wouldn't notice this in exhaust gasses - BUT mat=y cause rust / corrosion if expansion chamber,

 

most other leaks you would see externally.!!

 

personally I would clean everything and check / measure,  new O-rings, then give it a few short ( street / backyard) runs to check if it's watertight

 

 Charlie

It could also be a clogged spark arrestor screen, broken reeds, or clogged jets causing an overheating issue.

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