ebay HT bicycle engine teardown after 3k or so miles:

Discussion in 'Motorized Bicycle General Discussion' started by maniac57, Jan 16, 2014.

  1. maniac57

    maniac57 Old, Fat, and still faster than you

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    Finally took the old Pig bullet apart today.
    News was not good.
    Found LOTS of scoring on the piston and cylinder wall caused by flaking chrome in the bottom of the jug. Both rings were pinched and stuck from galling.
    Also had excessive play in the small end of the conrod. The pin and bearing looked fine, but the small end of the rod had worn to the point of allowing the piston to kiss the head and leave a ring in the carbon.
    I KNEW there was something going from the change in the sound at cruising rpm.
    It was starting to sound dangerous and scary when I replaced it, and now that I see the reason, I'm glad I did!
    Everything else looked brand new, which surprised me as I was expecting some slop and grinding in the main bearings. But the bottom end looked great aside from the aforementioned con rod wear. The clutch looked good too.
    I'm assuming the flaking was simply luck of the draw and my engine started life with defective plating as I ran my usual oil ratio the entire service life and have never seen this defect in any of my engines until this one.
    Still, 3-3 1/2k miles ain't too bad for a $150 kit engine considering.
    I'm saving the bottom end for parts since the mains and clutch are still in good shape. All the small parts are still useable too.
    I may measure the current small end diameter and see if I can find a larger bearing to let me try using this bottom end again someday without rebuilding the crank (which I don't have the proper tools to do anyway)
    Sometimes you're the windshield, sometimes you're the bug.
     
    #1 maniac57, Jan 16, 2014
    Last edited: Jan 16, 2014
  2. Toadmund

    Toadmund New Member

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    Re: ebay HT teardown after 3k or so miles:

    Pictures would be great.
     
  3. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    Re: ebay HT teardown after 3k or so miles:

    What oil have you been using?
     
  4. Jumpa

    Jumpa New Member

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    Re: ebay HT teardown after 3k or so miles:

    Can you take a picture of this "Flaking " I have one I just took off that has what i might consider the same. On the bottom of the jug it looks like dull aluminum compared to the chrome elsewhere in the cylinder
     
    #4 Jumpa, Jan 17, 2014
    Last edited: Jan 17, 2014
  5. maniac57

    maniac57 Old, Fat, and still faster than you

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    Re: ebay HT teardown after 3k or so miles:

    I tried to get some pics but my cheap phone cannot take one that shows anything except shine. The reflections wash out all the detail except the ports.
    Sorry.
     
  6. Toadmund

    Toadmund New Member

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    Re: ebay HT teardown after 3k or so miles:

    Sorry about pushing for pics, we just like moto porn. :)

    You seem to have painted some decent pics with your words though.

    I think my first motor got scoring and major catastrophic bearing damage, due to grit getting past my carburetor filter. In my case I have an RT carb that let grit in through the choke lever slit hole. Since then (and a new motor) I have glued the choke lever shut.
    I'd rather have less than ideal cold starts over a gritty motor. Perhaps I could make some sort of dust boot for it if I could be bothered enough to.
     
  7. maniac57

    maniac57 Old, Fat, and still faster than you

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    Re: ebay HT teardown after 3k or so miles:

    One thing that did impress me was the lack of any visible wear on the clutch. It looks as good as new even after my abuse. The mains still feel tight and smooth too, so it's kinda annoying that I can't reuse the crank without rebuilding the rod. :(
     

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