Help with bearings

Discussion in 'Motorized Bicycle General Discussion' started by PerryP180, Jan 12, 2012.

  1. PerryP180

    PerryP180 New Member

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    From reading multiple posts on this forum, I've determined that i need to replace what the post called my "upper conrad bearings". I got the bearings the forum member recommended. My big problem is that I don't know where they are located on the motor. The motor is dead so I was going to just tear it down until I found the problem. I've since decided that is a stupid approach. Can any of you tell me where on the motor these upper conrad bearings are and the proper names of any other bearings I might find once I get into it? Thanks.
     
  2. Al.Fisherman

    Al.Fisherman New Member

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    What engine?
    What bearing... the wrist pin bearing or the crankshaft bearing.
    https://docs.google.com/document/d/1BJQmfhKXxxZKV2swbg80BYJzzT8ySrtFwDKcNrdG750/edit
     
    #2 Al.Fisherman, Jan 12, 2012
    Last edited: Jan 12, 2012
  3. PerryP180

    PerryP180 New Member

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    I was so frustrated I forgot to mention the important stuff. It's a Grubee 66 cc. The posts I read kept referring to the "upper conrad" bearings having a high failure rate. My engine made it to 1600 miles and died. At around 1300 miles I started hearing a rattling or clicking sound. It was not piston slap. The noise gradually got worse and really bad moments before it died. It died while it was under throttle and it just totally died. I've since replaced the motor and the new one works great. This shows me that the problem is somewhere in the motor as that is the only thing replaced. These symptoms were just as described in the post about the bearing failure. The motor will still turn over but not start or even try. Do you have any other suggestions? In your opinion are the stock bearings high failure points?
     
  4. Al.Fisherman

    Al.Fisherman New Member

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    If my engine I'd first pull the cylinder off, and inspect the head, gasket, rings and wrist pin bearing. Then inspect the crankshaft/camshaft bearings (rotate crankshaft at the magneto nut), if it feels like a bearing, go ahead and open the case. Weather crankshaft or camshaft bearings, the case needs to be split.

    [/QUOTE]In your opinion are the stock bearings high failure points?[/QUOTE]

    I personally have never had a bearing of any sort fail on 6 engines, BUT there are other members that have had, numerous.

    Chinese HT breakdown pictures by Ron-Becker - Photobucket
     
    #4 Al.Fisherman, Jan 12, 2012
    Last edited: Jan 12, 2012
  5. rohmell

    rohmell Active Member

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  6. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Yes. They're upper con-rod bearings, as in "connecting rod". They'd be located at the upper end of the connecting rod where the wrist pin passes through it and the piston. Watch for snap rings holding in the wrist pin.
    If you remove the piston from the cylinder, you may need a ring compressor to get it (and its rings) back in. I don't know if the rings are pinned on the Grubee's 66 cc, but it might be safe to assume they are.
    When you tear her down, make sure that's your problem. Even a good fix is no fix at all if you still have the problem when you're done.
     
  7. Wally

    Wally New Member

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    Al, before I pull the head, I would do a compression check, The OP does have another engine he can compare it with. BUT it sounds more like broken rings to me.........
     
  8. Al.Fisherman

    Al.Fisherman New Member

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    Under different circumstances I'd agree. But with the noise that the engine is making there is more wrong. Weather or not it has good/bad compression, it needs to come apart. But a compression check if you gave a tester won't hurt.
     
  9. PerryP180

    PerryP180 New Member

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    I've pulled it apart except for the casing below the jug. I'm hoping to find the problem before I get to that. The rings look good. The bearing on the upper part of the connecting rod just fell apart when I slid it out of the hole. There is no scoring on the inside of the jug but there is a spot by the exhaust port about the size of a quarter where the zinc coating looks to have peeled off. It doesn't look scraped. What really worries me is that nothing I've seen so far would cause the motor to just die the way it did. Except for the rattling noise it ran great. This is leading me to think it might be the bearing for the magnet inside the magneto. I really hate to pull the magnet because it is my understanding that with that done I will have to reset the timing.
    Could the bad bearing in the connecting rod have hampered the piston motion enough to kill the motor? Does anyone know if the bearing on the bottom end of the connecting rod is the same size as the upper? The upper connecting rod bearing seemed to still work it was just so worn out that the rollers fell out when pressure was removed from it.
     
  10. Al.Fisherman

    Al.Fisherman New Member

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    That is a misconception. There is NO timing adjustment on "STOCK" magnetos, Although the magnet can go in backwards. To solve this problem with one already installed is place a mark on the side facing you, pull the magnet. BUT, although I have never had the occasion or inspecting the rod bearing, I doubt they are the same. Also feel (could be wrong) that the two halves of the crank are pressed together, without a press if the crankshaft bearings are bad, I think a new one would be the most cost effective.

    Installing the magnet on a HT
    Magnetto pictures by Ron-Becker - Photobucket

    Also other things could be wrong beside the engine noise to make it die.
    https://docs.google.com/document/d/1aBeJuoS--VQWwXysc07rpscTUbPzgc93xjiQBgsyFjc/edit
     
    #10 Al.Fisherman, Jan 15, 2012
    Last edited: Jan 15, 2012

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