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Discussion Starter · #1 ·
I picked up a 2006 TW 200 for $300. It was a basket case. I like projects and have done museum quality restorations in the past. My question is trying to find out if my engine is from this bike or something else. How do you determine it from the engine serial number? I can't find any info on it. The serial number is 3AW 109444. Now I got the bike assembled and went to fire it up. Cranked over and would barely pop at idle and nothing when throttle was opened. Checked the compression and it only had 55 lbs, so pulled it down and found the piston all scored and rings sort of welded to the piston on one side. The seller never had it disassembled but included one of those 70mm AHL piston kits so off to a machine shop to have the cylinder bored out!
 

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Discussion Starter · #2 ·
On further investagation the only machine shop that does small engine boring wanted $150 to bore the cylinder to fit that 70mm piston so after miking the cylinder which cleaned up well, I can get away with the stock piston so for now, that's the plan. Still curious about the cause of that piston siezing.
 

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Lack of oil and / or overheating.
Sometimes just sitting for a long time a ring will get stuck to the cylinder wall.
 

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Discussion Starter · #4 ·
Thanks for the reply. There was aluminum from the piston welded to the cylinder wall but I was able to run a hone through it and remove all of it and since the cylinder is still in spec, I'm going to try and put a stock size piston back in it and hope for the best for now. We'll see what type of compression it develops and if that doesn't work, I'll go to plan B.
 

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The oil filter that was in it when you got it. Did it have four holes or two on the side that goes to the engine?
 

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Either that, or someone fired it up after a long time without checking the piston ring condition first

"The wrong filter" can do this, but usually seizes the cam first, and the piston second, I'd suggest checking that as you will have the head off anyway

Possibly a flood damaged engine, but in any event, what you see is what you have to deal with - good luck ......
 

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When aluminum is deposited on the cylinder wall it usually is a result of over heating leading to an enlarged piston rubbing on the cylinder walls.
If piston to cylinder wall clearance is small it takes very little expansion. If the clearances are large it takes actual overheating, like air cooling fins plugged up with mud and hard riding to do the damage.
Since you will need a new piston anyway, get a Wiseco model 4292M06700, comes with rings, wrist pin, spring clips and use it in the cylinder you have. Its a foraged piston that ups the compression ratio.
Wiseco calls for a minimum of ,002" clearance. When I hone out a cylinder I set the clearance at .0025" to .003" and have had zero problems.
The wrong oil filter shuts off the oil flow to the top of the head. The lower end still gets lubricated.
 

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Discussion Starter · #8 ·
Thanks for the advice. Everything in the engine is in good shape except for the piston. Checked the oil filter and it was a stock Yamaha filter with the 4 holes. I replaced it with a K&N. Now waiting for parts to arrive so I can reassemble it.
 
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