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Discussion Starter · #1 ·
Just got a 98 Forman 450sw in the shop today. The owner said it was smoking and was hard to start then it wouldn't start. It had very little compression . Pulled the head and I could move the edges off the piston Up and down. Making the piston slightly crooked in the cylinder.. One side of the piston is worn bad. And there is a small amount of play in the rod side to side. How much play is to much play and what would have caused this?
 

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Side to side is normal.. up and down is what you don't want..

Causes, could have been sank, poor maintenance???


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Discussion Starter · #3 ·
Poor maintenance is probably the culprit. There is no up and down play so that's a plus. Just happy to rebuild a Honda again. Just rebuilt a 99 400 Kawasaki prairie without pulling the motor! Talk about a tight fit! Lol!
 

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Pull the cylinder and see what other surprises you find.. lol


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has it been sunk ?. lack of oil will cause a cylinder and piston burn out. cylinder needs to be bored one size over, this means new piston kit, top end gasket kit. check your valves for bent valves ?. replace the cam chain, you will need a front clutch cover gasket. new oil filter wouldn't hurt.
 

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Discussion Starter · #7 ·
Wasn't sunk to the owners knowledge. But was stolen then found it. Said it smoked after that and just ran it like it till she stop running. Knew it def needs a new top end. Wisco makes one I think. How hard is it to replace timing chain?
 

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Wasn't sunk to the owners knowledge. But was stolen then found it. Said it smoked after that and just ran it like it till she stop running. Knew it def needs a new top end. Wisco makes one I think. How hard is it to replace timing chain?
shindy makes a piston kit, namura does, and wisco. I use namura, great piston kits. cam chain is behind front cover, top end will be off, pull the cam followers so they won't drop down in the lower engine. make sure to check connecting rod for any play at wrist pin, and at lower connecting rod bearing ?, if the connecting rod is bad ?, a new top end won't last at all !.
 

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Discussion Starter · #11 ·
Forgot to mention I can't get the wrist pin out. Had to pound it with a socket and mallet. Seems to be warped. Think that caused it?
 

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Do a search on Namura pistons. Personally I think Wiseco is the way to go for the Foreman, or OEM. Shindy isn't bad.
wiseco is the best, but over priced, oem is great, but for the price of a namura ?, i'll keep using them, I like them.
 

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Forgot to mention I can't get the wrist pin out. Had to pound it with a socket and mallet. Seems to be warped. Think that caused it?
wrist pin is seized , means it ran low on oil for sure !. i'd bet the connecting rod is toasted !.
 

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Discussion Starter · #15 ·
Not putting any company down. But I've always used wisco when it was available. We all have preferences like Pepsi vs coke!
 

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Discussion Starter · #17 ·
The rod actually has very little movement. Doesn't look warped, bent, cracked or any overheating coloring. I'm more scared about the wrist pin hole!
 

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Not putting any company down. But I've always used wisco when it was available. We all have preferences like Pepsi vs coke!
if you want to spend the extra cash for a piston that will gain very little ?, go for it, nothing wrong with that :). I just cant see paying the extra cash for a high dollar piston in a utility atv, not when a namura, or shindy will be just as good, but hey, it's your atv, your cash, soooo..get-r-done :).
 

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The rod actually has very little movement. Doesn't look warped, bent, cracked or any overheating coloring. I'm more scared about the wrist pin hole!
if the top of the connecting rod where the wrist pin goes is bad ?, it's a bad rod, no way around it.
 
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