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Hi guys,

I posted a few days ago about a compression issue on a 2001 TRX400EX.

I removed the cylinder and piston tonight, and think I found the problem. There is a large abrasion area, on part of the cylinder wall, as well as the matching area on the piston. The rings appear to be worn down in this area as well.

I suspect the rod may also have issues. Before I removed the piston, I noticed that is was not freely pivoting on the wrist pin, it was rather stiff (was also a pain in the ass getting the wrist pin out). I can't visually tell if the rod is straight, bent, twisted, etc. There is some discoloration in the rod, but I'm not sure if that is normal.

As it is right now, I know that I'd be in at least a piston & sleeve to get this fixed. If the rod is shot, well there another couple hundred bucks.

I tried adding this to my original thread, but it did not appear to post. I will try and post the pictures in a reply.

Would appreciate any input!

Thanks,
Casey
 

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Well that piston seized in the cylinder at one point. The rod discoloration is normal. The wrist pin not coming out easy isnt necessarily a bad thing either. That means it fits tight so tolerances are probably pretty good. The new piston will come with a wrist pin anyway so if its slightly bent from the seizure thats no problem. The unknown is did it bend the rod when it seized? Is there any up and down play in the lower rod bearing?
 
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Hold it up to your eye and look down it, you will be able to tell.
 
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That's what I've always done. There may be a more scientific way lol
 

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Yeah no dont look down it like your looking down a 2x4 lol. I take a straight edge and put it on one side and mic the seperation between the straight edge and the rod small end. There in all honesty is no better way i am aware of. If it were me i would just change it. Since the piston seized. If it wasnt for that i would say run it. But seizure is never good.
 
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