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Discussion Starter · #1 ·
I have a 1987 fourtrax 250 with a slight metal to metal knocking sound in the head when at idle. I took the head apart to check the rod but found no play in it. The wristpin also seems to be fine. There is no up , down looseness I can find that would cause the knocking. Any idea? The knocking is only heard at idle and sounds like metal to metal slapping. Like a rod knocking but not as loud or hard.Not a tapping like a cam chain more of a slapping of metal. As far as I know the engine is all stock with maybe new rings.
Thanks for any Info.
 

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Discussion Starter · #4 ·
Hey, I checked the valve adjustment before I broke down the motor hoping that was it, but it was set right plus the knocking was more in the bottom end. I think the previous owner checked the valves too. They were set right on .007 mm . Let me ask you guys this: Should the wristpin have any play in it? Thank you for reading and trying to help. I know its hard to tell someone what the problem is without being there, but yall give me new ideas as to where to look.
 

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Discussion Starter · #9 ·
Ok. Sorry for the late,late reply. I got it back together. I honed the cylinder, new rings, and timing chain. It run great. I'm thinking the timing chain had more play than I thought and was hitting the head. I did put a new wristpin in it which got rid of the little play I was having. I still have one more problem I think. Do they always run so hot? We were riding them in the woods and at a idle I heard a hissing sound. I turned it off and the sound was coming from the gas tank. When I open it the gas was boiling. We now have 2 of these 4wheelers a 87 and 85 both get hot like this. What do you guys think could be causing this or is this normal?
 
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