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  1. #1
    Pistonwash's Avatar
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    About your cranks.

    I will put this information on the how to forum, but here first to let you know something important imo.


    Looking at Insandiego's crank on the For Sale forum, I noticed a common sight when viewing a used GPR crank, you will see "chatter" marks on the crank bearings that are set in by pins. These are the thick bearings that are assembled to fit in the cases with set pins you rotate a certain way when you install your crank into the cases.

    These thick bearings will fit kind of snugly into the cases but as you can see, they will vibrate with crank rotation and cause a discoloration because of the vibration. I believe as does Mr. Lowell, that this contributes to stress on the crank. The solution?

    I use, as does Mr. Lowell something called tight tolerance Loctite, he had a specific part # that he gave me..when I went to my local Loctite dealer, he informed it was the green Loctite that is used for this type of re-assembly.

    What the Loctite does is make sure the two surfaces (crankcase & bearings) have a tight fit with no vibration being transferred into cases.
    I believe when you re-assemble your cranks into the cases you need wipe a thin film of the green Loctite to help prevent any "chatter" marks from forming thus preventing premature crank failures imo.

    Anyway..this is the way I put the engine back together..anything to help th crank keep from stressing is a plus.

    Here is the product, so when you re-build, follow the instructions and use this product to help prevent crank failures.


    http://www.loctiteproducts.com/produ...id=48&plid=695

    Hope that helps.


  2. #2
    Hydrotoys's Avatar
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    Remember, he has gone through 2-4 snouts, due to a bad flywheel, as well as breaking a Rad Charging flywheel. Only a balanced flywheel with the radiused back side stopped all the carnage.

    Note that is the factory style front bearing. Note the small area where the bearing actually rides. Very weak setup.

    Also, note the discoloration on the front rod. Either it was getting wet... a lot, or that is heat discoloration from an air leak. Joe went through a lot of water issues, and may have been overpressurized.

    That style bearing used orings which were chewed up. I'd imagine the chatter followed quickly.

  3. #3
    Moderator Insanediego Joe's Avatar
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    holy shit im famous or err is that infamous?

  4. #4
    Moderator Insanediego Joe's Avatar
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    #1 got a good drenching when the cylinder lifted off of the case. This happened atleast 2 times. The water shot right through the carb into the cylinder and right back out through the bottom.
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  5. #5
    Thanks Piston great info i am getting ready to put my motor back together.

  6. #6
    Pistonwash's Avatar
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    Quote Originally Posted by Insanediego-gpr
    holy shit im famous or err is that infamous?
    Actually Joe..that crank looks very normal. The crank that I sent to Phil at Crankworks to get re-built looked just like that one. The vibration on these suckers is enormous..radiusing the snout, lapping the flywheels and when re-installing the cranks use the Loctite is a must.

    Do what you can to eliminate the play and vibration, longevity will follow.

  7. #7
    xyzyx00's Avatar
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    does anyone have a snout support for sale? can i get a new one anywhere?

  8. #8
    All hail the Chief! fullboogie's Avatar
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    Great info Mike - thanks!

  9. #9
    Moderator Insanediego Joe's Avatar
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    I have a front cover that is modded with the snout support. Your gonna need new bearings for it. availabe thru ee gads am i doing this nobleracing.com

  10. #10
    Moderator Insanediego Joe's Avatar
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    I also have my special sauces flywheel.

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