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Cylinder Wear

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I just rebuilt my 300 XCW top end. It looked pretty good when I took it apart, just some minor scuffing. I put it all back together and rode it for about 3 hrs. At around 3/4 throttle i could hear a rattle towards the front of the engine at the exhaust/power valve area. So i pulled it apart and this is what I found:

photo-1.jpg

What is wrong?

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Nope. I oiled it and warmed it up a couples times the day before.

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Possibly. I replaced the head with a Slavins Mule head. Would I need to richen it up? If I do need to richen it up, do I do this with the main jet? I am running a 160 main so should I go up to a 162?

Also, could a wrist cause this? I pulled the old wrist pin bearing and it seems ever so slightly tighter.

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After rechecking, I dont think it's the wrist pin bearing. I inserted the pin thru the bearing and it feels pretty good and secure.

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Did you mess with the Z dimension at all? The power valve flapper looks shiny like the piston was rubbing it slightly. That piston has a lot of carbon for only 3 hours.

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Did you mess with the Z dimension at all? The power valve flapper looks shiny like the piston was rubbing it slightly. That piston has a lot of carbon for only 3 hours.

Didn't mess with the Z dimension. I cleaned the sh*t out of the PV so that's why it looks so shiny.

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I had slavens do my and replaced the hockey stick with an EE. I had to go up several sizes on the main and pilot

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What year is the bike? It looks like normal wear.

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What year is the bike? It looks like normal wear.

2011.

It wasn't there when I pulled the first piston out to do the top end. This is the first top end on this bike.

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Plug looked fine maybe slightly lean as in the white porcaline area was still white but it was brand new and did not look like it was super lean.

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I think I found the problem. I got a top end rebuild kit from Rockymountainatv. The sent me the wrong gasket and seal kit made by Tusk. All the gaskets and o-rings were wrong. All of them. I had to order the gaskets from Slavins and I reused the 4 power valve seals. But the head o-rings looked right. Well I was wrong they are leaking coolant past the inner o-ring into the cylinder/piston area right down the front of the cylinder. I think the rattle I hear is the PV because the o-rings there are also probably the wrong size.

What a bunch of crap, rockymountainatv. Never again!

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Just FYI,

after slavens decked, ported reshaped my head I had to increase the pilot size to get rid of the ping that his work created. It was detonating due to being lean on the pilot, and I'm at 6200 ft ASL. I went from a 35->38. If you are at sea level a 40 pilot might be better.

The rattle you hear does not answer for the skuffing on the front of the cylinder. I think you either have a piston that is too big for the bore (did you go to a #2? did you measer clearance before installing?) if it's a tight fit make sure to warm it up good and slow.

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