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ptorresavello

YZ426f smokes, cylinder full of oil. HELP!

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Hello, My name is Pablo, I'm from Chile and this is my first 4 stroke, I bought this bike from a guy who bend 4 valves after a full rebuild, but he didn't replace the timing chain, damper and tensioner. I took it home and bought springs, valves seals and took the head to a shop so I would just install it and set timing. The cylinder looked OK, not great but useable(iron sleeve, plating doesn't exist down here, all the bikes run steel and do OK), the piston and rings had just a few hours, and the rod too, the bike was running great until the chain slapped. When I installed everything(with the ring end gaps where they belong), second kick and it ran good, but the blue smoke just didn't stop, it was like the bike was on fire. Did a test run and damn it pulls, nothing compared like the cr250r I previously had. The compression is great I can't get pass the compression stroke without the decomp lever(I'm 240lb), but the oil out the exhaust kept going, so I decided to take everything apart and start all over again. With the help from a friend we re installed the cylinder and found out that the piston pushes oil trough the rings up to the combustion chamber in every stroke, like the oil was under pressure, even after when we drained almost all of the oil out of the engine. This was done by pushing the kickstart lever with only the cylinder installed, is this normal?. After all of this we honed the cylinder because it seemed glazed and re installed everything hoping that the rings would settle this time. First couple of kicks and it ran ok but died after a few seconds, then again holding the throttle and started to rev it up over some dunes, when I was getting back to the truck I noticed water everywhere, the head gasket was leaking and the base gasket was literally blown away from it's place by all of the compression that the crankcase is holding. The oil level wasn't even at mid.

What the hell is wrong with my YZ? Please help!

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The crankcase can't retain any pressure without the head on it because it's open to the ignition flywheel chamber which is open to the cam chain tunnel which is just open.  The '01 has no oil pressure feed up through the cylinder (it's outside on the oil manifold).  It sounds like you may have failed to but the ends of the oil ring expander together before placing the oil rings over it. 

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that's the one in the middle? between the two other small oil rings? I had trouble installing it because it wouldn't close, and was impossible to put the cylinder down, so I chopped a bit so it could be done. Could that be my problem? I thought the oil rings were there just to spread oil on the cylinder wall and the 2nd ring was supposed to maintain the oil down in the crankcase away from the combustion chamber.

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that's the one in the middle? between the two other small oil rings? I had trouble installing it because it wouldn't close, and was impossible to put the cylinder down, so I chopped a bit so it could be done. Could that be my problem?

 

Well, yes, that is the problem, alright.  Get a new set of rings and install them the right way. 

 

No, the oil rings are supposed to keep oil from below the piston out of the combustion chamber.  They are much more difficult to drop a cylinder over than the compression rings are.  It's the only way they will work.

 

You're going to need a new head gasket and base gasket, too.  Don't try reusing the old ones.

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ok thanks a lot!!, I'll let you know if my problem was resolved!! I hope I can get a new ring set here in chile, or just wait a few weeks if I have to bring them from the U.S

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I found a ring set in Chile, I'm waiting for them. Is there any other thing that could cause the problem I'm having? some clogged oil conduct or something?, I cleaned both filters already.

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Not really, no.  You have to understand that by shortening the expander, you took all of the tension off of the oil rings.  They could not have worked.

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Not really, no.  You have to understand that by shortening the expander, you took all of the tension off of the oil rings.  They could not have worked.

Grayracer, I finally got a new ring set and a new head and base gasket. Tomorrow mornign I'll start with the assemmbly and I'll let you know how it goes.

 

I posted a question in the general forum but no one answered. I'm gonna be in the US and I think it would be great to buy a bike there, use it for the month or more that ?im staying and then somehow ship it or take it in parts back to Chile, could you help me with that? do you know anything about this subject.?

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