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  1. #1

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    Piston pin clip/circlip question?

    I am rebuilding an almost new SBT GP1200R engine which had a broken piston, bent rod and damaged crank. On said engine, the SBT pistons have internal circlip retaining rings for the wrist pins. On the undamaged piston, one clip was walking out of its groove, causing speculation that was the root cause of the other cylinders demise. About half of the rings were put in with the rounded edge facing out, which I believe is not the best choice. I have been advised by one respected mechanic to replace the clips with Yamaha spiral retainers which would be more reliable. My thought is the groove in the SBT piston is squared, where the Yamaha is round. Would the round retainer be fine like was suggested? I don't want to take chances, this problem has already caused a complete rebuild.


  2. #2

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    Quote Originally Posted by LT1GMC View Post
    .............I don't want to take chances, this problem has already caused a complete rebuild.
    What brand of piston does SBT use, and what do THEY recommend for their pistons. More than likely, your mechanic is correct.

    The real question (if you have serious concerns about SBT's pistons and circlips) is why would you even consider reusing them in the first place, knowing you have problems with them before, and that the OEM Yamaha pistons will get it done with no issues at all?

    I know that pistons are expensive, but look at all of the grief you have because of them.

    Excuse my rant, it is just that when it comes to the 66V engine, SBT has had less than a stellar record. My SBT crank lasted every bit of 15 minutes before it went south. I took a harder look at the seals that they sent me and they said "Made in Albania". I looked for weeks and couldn't find an Island or city in Japan called "Albania".

  3. #3

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    Well, you do have a point. I was thinking of reusing the 2 SBT pistons because they are basically new, but so was the engine and it had leaks at the "new" rear seals, and the front seal had the spring laying loose next to the flywheel.
    I "think" the failure was due to some of the circlips being installed wrong and one walking out, but the engine was probably destined to a short life anyway with the leaks. Oh yeah, on a cylinder that was not damaged, the PV pin had fallen out and was laying under the shaft, do not know why the PV had not dropped and hit the cyl.

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