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Discussion Starter #1
I am going to replace the leaking base gasket on my 2006 TW200 soon. I have read and watched the videos on doing this. My question is why take the wrist pin out and remove the piston with the cylinder? The new base gasket should fit over the piston. I would think it would be a good time to inspect the piston and rings (Old two stroke rider ?)? I have all the parts but I didn’t purchase the wrist pin clips. I also have the piston ring install tool.
 

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I think it has do do with the way the rings are worn in to the cylinder walls. Once you remove them, they won't go back the same way, and they'll have to "break in" all over again (if they even can). At that point, you might as well just replace the rings, and hone the cylinder.

You can re-use the wrist pin clips, if you don't bend them or lose them when you take them (only one side, actually) out. A dental pick is helpful during this operation. An extra set of hands would also be helpful, but it's do-able alone.

Also, if you do remove the piston from the cylinder, you don't really need a ring compressor to re-install it. The bottom edge of the cylinder is beveled, and it's pretty easy to squeeze the rings enough with your fingers to get them to slide in the cylinder. Installing rings on the piston can be done by hand as well.

Have fun! :)

EDIT: My bad, I thought you said you did not have the tool.
 

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I don't know if you're aware of the issue with the base gasket oil leak due to unevenly machined engine halves - if not, you may want to check the respective threads. I solved this leak on my bike by sanding the surface slightly at the problematic area (closer to the front of the bike, I was able to feel the "step" with my finger).

I did the disassembly as per the mentioned video, by removing the wrist pin. It was quite worn, I had to replace it. Could not procure one for the TW, so had to use the same 16mm from a Daewoo Matiz and cutting it to length.
 

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I just pulled the cylinder off the piston and replaced my base gasket. I had the cylinder checked and it was in spec. I didn't want to wear it out any so I did nothing. I stuck it all back together. I rode it around and no issues. I am still riding strong with no piston or ring replacement.
 

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Try re torquing the head bolts. Remove two at a time, clean and lube them, preferably with case lube if you reload, and torque to spec. I have done this several times and 9 out of 10 times the base gasket leaks is cured. Quick, easy, free. Well worth a try.
 

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There is no problem reusing the rings if it had good compression and does not burn oil. It does not matter if the rings get turned, they rotate slowly as the engine runs so that is not an issue. It is just easier to get the piston out of the way otherwise you may damage the gasket. (unless you have 3 hands)
 

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Discussion Starter #9
I finally got around to replacing the base gasket on my 2006 TW. It went fairly well. The gasket was definitely bad. The case halves are uneven on the back where the cylinder mounts. I noticed that’s where Yamaha adds the extra gasket sealer on there new base gasket. I smoothed/lapped it down to help seal. A couple of problems I ran into: there are three timing marks on the flywheel, turning the flywheel counter clockwise the first two are connected by another line (like a H). Then the third mark is by itself. That mark seems to be closest to TDC. (My TDC gauge doesn’t fit that size spark plug hole so I put a pencil in it and just felt for TDC.) Is that the right mark? The next thing when I was messing with the timing the chain fell off the lower sprocket on the crank. I finally got it back on, but is there a easier way, I just used my fingers and messed with it until I got it. It’s been a long time since I had a four stroke apart! I mostly work on two strokes. Not too bad to work on just different. Next one will be much easier! I’m just glad I never had to rebuild my KTM 450 RSF!
I also have a 2009 TW that is leaking but not near as bad, I will try retorquing the head on that one before replacing the base gasket.
I also removed the Welch plug that covers the low speed screw on the carb. Mine was turned out 2 1/4 turns, how many turns are people starting at?
Thanks
 
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