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  1. #1
    Robsauto2's Avatar
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    ? for top GPR engine builders

    I bought a new GPR crank and had it trued-welded by Pro-Tec. It seems to have lost rpm from last season with the old crank. I am pulling the motor tonite and want to try to check the indexing of the FRONT crank snout. My thought is that it is installed slightly retarded causing the ignition timing to be retarded. Can anybody tell my it there is a way to check this? Again, not the indexing of the crank pins, just the nose piece that the flywheel bolts on to.


  2. #2
    WATER WOODY's Avatar
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    Pro-Tec does all my cranks.They check the index before it gets boxed up for sure.How many rpm's are you missing? What was the air density at that time compared to this time? How do your plugs look?There are multiple things that will cause rpm loss.The biggest is the weather.

  3. #3

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    guess you could do tdc on coupler and see if off,use timeing light
    how many hr's on new crank?

    later cd

  4. #4
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    From 80 degree weather to 60 I gained 1.5 mpr. I know it sounds nut but, I went from just barely beating my freinds rxp to kicking his but.

  5. #5
    Robsauto2's Avatar
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    OK, engine is out. Does anyone have pictures of the correct gas powervalve installation? I might have installed them wrong! Bought these valves from Fernando, not riva.

  6. #6
    spud's Avatar
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    Rob,

    If you want to use my spare crank your welcome to it. Joe was spinning it fast with the tripples. It is a fresh crank.

  7. #7
    Robsauto2's Avatar
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    Jim, I measured the modded flywheel vs the new wheel, and the modded wheel has the "firing triggers" (or whatever you call the bumps on outside) about .020" retarded fron the new wheel. This means the outside of the modded wheel somehow slipped during the machine process to lighten it. I have seen that on car engines a lot over the years. So we will see what a difference it will make this weekend. It may only be about 3-5 degrees. But maybe this is it? Well see.

  8. #8
    XL1200Ltd-Keith's Avatar
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    gas valves

    The groove in the powervalve faces down.

  9. #9

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    Quote Originally Posted by XL1200Ltd-Keith
    The groove in the powervalve faces down.
    And after you install it complete with the bellows attached to the plastic cap, put the black cover on and then reach into the exhaust port. Push the valve all the way up to make sure that you have 100% travel. The valve ought to go all the way up and the exhaust port ceiling ought to feel smooth... as if the valve were not there at all.

    If you install it in backwards, the valve will feel pointed when it travels all the way up into the exhaust port ceiling.

  10. #10
    Moderator OsideBill's Avatar
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    Rob,
    Spud loaned me a spare cylinder and piston to set mine up, and check for proper fit and clearance to piston on the bench prior to install. Do you need it? let me know I can drop it off. I am not going to install my valves until this weekend. I also have some pin gauges to check clearance.

    OsideBill
    760-672-0989
    Last edited by OsideBill; 09-13-2006 at 02:32 AM.

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