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  1. #1
    srjrinc's Avatar
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    Going on 3rd rear main seal!!!

    So I have this GPR 1200 with Speedwerx Head, triple pipes, Novi's ect.
    First Rebuild, running lean on rear piston , scored the jug & replaced but did not do Leak Test!
    Big mistake.... Second time, replaced rear main seal with Some "No Brander"
    seals on E-Bay, was fine on leak test but leaked & ran Lean again, but caught it
    in time. 3rd rebuild, got OEM seals fine on leak test but ran lean AGAIN!

    Wha's UP ??? any input???

    I checked the crank for deflection....
    .001 thousands on PTO & .004 on Mag . NO groove condition, just a line over the seal riding surface.


  2. #2
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    You say seal as one, there are 2 seals in back inner one sealing lip faces forward, outer sealing lip faces back. I can not see 3 seals going bad.

  3. #3
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    Ck the rear pipe for water leak. Pressureize the water jacket to 15 psi and look for a leak.

  4. #4
    srjrinc's Avatar
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    Quote Originally Posted by JIM'S PERFORMANCE View Post
    You say seal as one, there are 2 seals in back inner one sealing lip faces forward, outer sealing lip faces back. I can not see 3 seals going bad.
    I meant only the 2 rear seals. & they are positioned correctly. I will check the rear pipe like Rocketman suggested.

  5. #5
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    O and btw most of the time when a cylinder seizes on a triple pipe boat it cracks the cylinder beteen the exaust and transfer port. The renick company will NOT ck that. So again pressure testing the water jacket on that cylinder will find that. That will also make it seize again

  6. #6

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    Did you leak test with reeds in place? Some of the aftermarket reed sets have show to be troublesome at times, especially if you overtorque the two bolts between the carbs.

  7. #7
    srjrinc's Avatar
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    Quote Originally Posted by LT1GMC View Post
    Did you leak test with reeds in place? Some of the aftermarket reed sets have show to be troublesome at times, especially if you overtorque the two bolts between the carbs.
    that's another good point. it seemed to be fine on the last leak test. its just the rear piston has been so troublesome. not only is it running lean but also hotter than the other 2. may this have anything to do with my lean
    situation?

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