Bad vibrations

Discussion in 'Motorized Bicycle General Discussion' started by Flounder, Jul 20, 2010.

  1. Flounder

    Flounder New Member

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    Hey people.. Time to scratch your heads for me. I could use some help here..

    I was breaking in a new motor and when I was half way through my second tank it developed a nasty vibration. It occurs mid rpm range.. I have checked everything I could think off. Such as carb , head gasket & bolts , gas/ oil mix , mounting brackets/bolts and so on.. My hunch here is it could of just been a lemon from the get go.. It seem to be coming directly from the motor. It acts like a burnt valve but not seized up ..

    I'm going to wait a few days to see if anyone can help me trouble shoot this before I tear the motor down... Thanks in advanced!
     
  2. captainrichhill

    captainrichhill New Member

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    Well no valves in these motors. Could your engine be too rich and it's "four stroking"? Check your sprockets (both). Maybe you threw a tooth. I wouldn't run it though. If you can't find the offender, then you're gonna have to look inside. you could have a loose connecting rod or something.

    Let us know what ya find.

    Rich
    (south Jax Beach)
     
  3. Flounder

    Flounder New Member

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    Captain, in my post i was actual thinking burnt rings not valves, sorry. It very well could be a connecting rod..Great observation! thx.

    the c-clip is 1 down from the top.
     
  4. wezwheels

    wezwheels New Member

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    did you use the factory motor mounts? if so, you may want to do a little work on cupping them out in the direction of the frame tubes. some times the motor mounts don`t sit as flush to the frame as you may need. check your chain for any binding or links sticking. make sure your sprockets are lined up they may cause a wobble or a vibration if not in line. the muffler will vibrate if its free hanging with out extra support. just try anything out of the norm. after all, these are not your normal engines. next is the motor, there is a break in period. its going to take more than a tank or two to break in the motor. start bye making small or short runs,or just warming up the motor for 5-10 mins. then shut it down and let it cool. these are not sleeved cylinders. there junk metal and you have to cure the cylinder a little at a time to avoid issues later. your probably getting the vibration at around 23-25 mph would be my guess? that`s what is the norm until full break in. don`t push it to high in the rpm range at first. give the motor time to cure in. if your set on pulling it apart, make sure you have an extra gasket for the bottom of the jug. they tend to rip. just take the head off and check for anything out of the norm or anything that don`t look right. slide the jug up a little, but not past the rings. try to oil the crank end of the connecting rod. just a little should do it. there is going to be some slop of the connecting rod. after all this is not a real high quality motor to begin with. check for any connecting rod bearings possibly floating around. their junk and they tend to come apart early in the running. just to make sure the bearings are still solid. after you put it back together. start looking for other crazy type things that may cause the vibe. there is nothing to crazy to look for, the smallest thing will throw a motor to the wind. have a good one and wait to ride hard on that new motor. wezwheels.
     
  5. Flounder

    Flounder New Member

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    Thx Wiz for all your input.. I'll keep everyone posted on what I find.. Peace!
     
  6. Flounder

    Flounder New Member

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    Guys, I havnt took the motor apart yet, but I gotta tell ya .. It sound good at idle. Its when I advance the throttle that this vibration get bad im mean BAD.. I took the engine off and shook it around.. I dont hear anything busted or loose... Who knows... As soon as I find the clutch tool I'll bust it open for more obvious causes..
     
  7. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Hmmmmm.... this one should be interesting.

    Is it still running right, but just suddenly developed a vibration?
     
  8. Flounder

    Flounder New Member

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    Hey Joe, yeah, it runs good and sounds sweet. I've been running 20-1 gas oil mix, and Ive broke in a few engines before.. you can tell when these motors are broke in.. They turn into a real beast. This thing has me stumped..
     

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