Big problem, engine locked back wheel wont move

Discussion in 'Frame Mounted Engines' started by elwood, Apr 16, 2007.

  1. elwood

    elwood Guest

    was pushing the bike round to my grandmas house about 3 streets away was rolling it on the clutch, then let out the clutch to here its sound, (i had done a pedal test before with no problems )I had no spark plug in as the bikes not complete but it rolled about 3 yards then froze up, there is some movement in the piston as you can here it pop about 1mm each way but no more, the clutch arm moves but the front sprocket will still not turn.
    any ideas?


  2. gone_fishin

    gone_fishin Guest

    remove the clutch-arm cover & check to see if the chain is bound up on the drive sprocket, it's a common problem with a new build.

    when adjusting the drive chain for the first time, roll the bike back and forth while pushing up on the chain-tensioner, it'll find it's place where everything's just right, then tighten the tensioner. then, roll the bike w/o the spark plug to double-check before applying power or you just might break your chain or worse.
  3. elwood

    elwood Guest

    thankyou, it was locked up around the sprocket, I think the tensioner came loose! thanx for your help :) i will check before making further posts.
  4. azbill

    azbill Active Member

    good call augi
    you beat me to the punch
    8) 8)
  5. gone_fishin

    gone_fishin Guest

    "chain locked on sprocket" syndrome is an easy one, whoever got here first woulda fixed it for him :p
  6. Jon Kimball

    Jon Kimball Member

    I think i may have same problem. My front sprocket moves but then gets stiff and hard to move but then it goes back to normal but this happens every revolution. Im thinking about losing a few links and flipping the rear sprocket so that the teeth are as far from the wheel as possible to line up better with the engine. Does anyone have any input as far as the direction im taking with this? Could it be a different problem? Any suggestions and advice would be appreciated.


    EDIT: I cant get the chain out of the front sprocket either even when i take the clutch cover off
    Last edited: Jul 6, 2008
  7. KilroyCD

    KilroyCD Active Member

    It's been a few years since I've built my two-stroke bikes, but back then the engine kits came with two drive sprockets. One is for normal gauge bicycle chain, the other (thicker one) for heavier 415 (or similar) chain. Check to see which sprocket you have installed. It might be that you've got a standard gauge chain on the heavier drive sprocket. Also, another thing that I saw a few years ago was that sometimes the sprocket wasn't finished properly and the teeth were too long, causing the chain to bind. They needed to be ground down a bit. I'm not going to mention which vendor's engines I heard this being a problem with, but they are still actively selling engines.
  8. Jon Kimball

    Jon Kimball Member

    Thanks. I have put about 50 miles on it though already and this just happened today so Im still stumped