wrist pin bearing

Discussion in 'Motorized Bicycle Trouble Shooting' started by mike carter 2, Jul 21, 2016.

  1. mike carter 2

    mike carter 2 Member

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    does anyone know what a bad wrist pin bearing sounds like mine bike is makeing a weird sound when i lug it down
     
  2. sbest

    sbest Member

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    Typically they "rattle" in "no-load" situations.
    Wristpins rattle, big ends rumble, as you let off the throttle and take load off the engine.

    Steve
     
  3. mike carter 2

    mike carter 2 Member

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    thanks steve but that wasnt the problem i had the needle in the carb set to lean it was detonating bad sounded real bad
     
  4. sbest

    sbest Member

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    Ahhh, so how would you describe that noise for those interested?
    "A tinny rattle getting louder as you give it more throttle"?

    Some of us are like wine connoisseurs, but to the automotive industry...

    Steve
     
  5. mike carter 2

    mike carter 2 Member

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    i have a steep driveway i have to hit it speed to make it to the top rite at the top the motor has lost rpms to the point its pulling as hard as it can mabey 100 rpms a tinny rattling sound comes frome the top of the motor
     
  6. mike carter 2

    mike carter 2 Member

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    it also happens when i lug it around at real low rpms under 10 miles an hour like around in a parking lot im also looking at my exaust i just installded a cr machine header kit on my chamber there are 2 springs that hold the chamber to the jug mabey rattling there? it didnt do it before
     
  7. crassius

    crassius Well-Known Member

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    there is a LOT of backlash in the drive gears when going slow
     
  8. mike carter 2

    mike carter 2 Member

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    thanks i will regrease my gears mabey it will help
     
  9. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    I vote pre-detonation.
     
  10. mike carter 2

    mike carter 2 Member

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    Bikeguy Joe any idea what my next move should be
     
  11. crassius

    crassius Well-Known Member

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    stop lugging it in parking lots - roll up a bit of speed, then pull clutch and coast a bit, lather and repeat

    when going up hills, try to adjust throttle for the power peak (where it sounds nice & 2-strokey) - help out by pedaling a bit if revs get too low
     
  12. mike carter 2

    mike carter 2 Member

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    its a gasbike gt 80 kit on shwinn blackwell cruser bike high c head reed valves ported jug ported piston tranfers matched to cases 1979 rm 60 x chamber i sanded about a gasket and 1/2 off head to raise compression running reg gas at about 40 to 1 oil mix gets to over 35ish mph pulls fairly hard from about 7 or 8 all the way to top end almost forgot 40 tooth cog trying to build some tork into it
     
  13. crassius

    crassius Well-Known Member

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    one gets torque or speed, not both
     
  14. sbest

    sbest Member

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    I'd suggest cutting some squish area into your present head and gap it to 0.020 to0.035".

    Cut a 4" radius out to 40 or 47mm and set the gap by filing and sanding down the cylinder, or leaving off the head gasket and sealing it with Teflon tape.

    Steve
     
  15. salorr33cc

    salorr33cc Member

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    speaking of wristpin bearings, i was wondering same thing,, i heard they were having trouble with earlier wristpin bearings falling apart,,, i have a 09/09/2015 gt5 38mm stroke engine,,,i have looked at wristpins and it seems like there are three types,,, here are pictures of two,, the one is what came in my engine,, the other style is sold by JNM motors,,, should i change to different style,,, the third type has smaller length needles and more solid cage material,,,, and what size drill bit do you use to drill out wrist pin for less vibration ???
     

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  16. mike carter 2

    mike carter 2 Member

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    well i do belive i fixed it it was the header vibrateing when the ingine hit hard while pulling a load the cr machine header has 2 springs that hold the header onto the exaust mount i think the springs are letting the exaust bounce on the mount i made a new brace for the x chamber noise is gone thanks for all the info i learn new things every day
     

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