Why am I breaking my chain?

Discussion in 'Frame Mounted Engines' started by TheMightyGoat, Apr 8, 2011.

  1. TheMightyGoat

    TheMightyGoat New Member

    Just got my first build together last night. It was time to test it for the first time, so I decided to do a pedal start. I got up to speed, dumped the clutch, and *chugchugchugchug* was the only sound of the compression in the engine as the wheel turned - no start. I was preparing to try again, when a new sound was added - *ping* - as the chain broke.

    I got it back home and saw the master link had come apart (as well as lost a roller in the chain). I replaced the roller with one from a scrap link of chain and put my spare master link in. I thought perhaps the chain broke because it was too tight, as I did get it pretty snug on the roller, so I let some tension off and decided to try again with the bike jacked up and the rear wheel off the floor in my garage.

    It still wouldn't start, but that was a different issue. Some failed kicks and fiddling with the carburetor later, I kicked the pedal and the engine came into life for the first time. The rear wheel spun, suspended off the ground. I was beginning to fiddle with the choke when a more horrible crunching and sapping noise occurred and the engine stalled. This time, the chain had come off the sprocket on the engine side. I took the cover off and began to feed the chain back through (surprisingly the master link stayed in place this time), which was when I noticed that one of the links was sheared completely in half on one side. I decided to stop fiddling with it for the night.

    So, why is my chain breaking? Is it related to tension on the chain? Or is it more likely that it is due to alignment from the hub sprocket? I put one of my rubber pieces on the outside of the spokes and one on the inside, in spite of the included directions instructing me to put both of them on the inside, because the chain seemed to line up better with the engine this way.

    Also, should I replace this new break with another master link, or should I go buy a new chain?

  2. bobprobert

    bobprobert New Member

    it's possible you have the master link on backwards. make sure the open end of the clip is facing the rear tire while on the top of the chain loop
  3. bobprobert

    bobprobert New Member

    also you need to put both rubber pieces on the inside of the spokes
  4. TheMightyGoat

    TheMightyGoat New Member

    Why is that? I can change it, it just didn't seem to line up as well that way.
  5. FylingScot

    FylingScot New Member

    What engine do you have? 49cc or 60cc
    What chain are you using? I understand that there is the standard 410 chain and a heavy duty 415 chain.

    I am doing my first build but I have the Sick Bike Parts jack shaft connection to my rear gears and a 66cc Grubee GT5 Super Rat engine. I have broken the short chain from my engine to the jack shaft twice in a week. No sheared links so I assume I just pulled an outer link apart with too much torque. I have the standard 410 chain and I figure I need the 415.

    BTW - is there a chance of you having a flimsy frame such that the chainstays bend under load causing increased misalignment? When you pedal a bicycle hard out of the saddle you can causing the rear wheel to move closer to the left chain stay so I would imagine an engine could cause considerable flexion of the frame.
  6. sounds like there is some serious allighnment issues.

    have the bike off the ground and pedal in high gear. see if wheel is straight. i found that the wheel may look straight on its own but when that gear for the engine goes on it looks really out.

    by the way you say the chain is snapping it sounds like its pushing against one side of the sproket. try putting the rubber spacers on as its been said before and try the process again. even s slight change is enough. if its not working the way you are doing it then maybe your eyes are out and the chain is not. have had a 410 chain on mine and its fine. not a single sighn of wear on the chain and its done some off roading when testing.

    have noticed that 2 strokes are really tight to start and ive been sent into the tank a few times.
  7. HeadSmess

    HeadSmess Well-Known Member

    hmmmm, bent tooth on the sprocket?

    chain too loose?

    wheel skewed in the frame?

    sprocket not concentric?

    its a doozy :)

    the chains are usually fairly tolerant of a little mis alignment... but then again, not always. place a straight edge on the sprocket and check it... the engines not so critical, and theres not much you can do about it... so concentrate on the wheel...

    umskies...so. um. well, youll be getting a new chain... it might have just been POS? and then, finally...

    make sure the tensioners in line too...
  8. DingoGoneWild

    DingoGoneWild New Member

    Chain Breaking

    I have had my bike for a year and a half now. lol... Hasnt even gone 3 blocks because the chain keeps breaking. Thanks for the pointers, Ill make sure the master link is on the right way and try to get her aligned good.

    At first I thought the chain broke because the clutch would not go into neutral... would a clutch problem cause the chain to break?

    If my chain breaks a third time im going to run the pos over with my monster truck. haha jk
  9. DingoGoneWild

    DingoGoneWild New Member

    Chain Breaking

    So I built a second motorized bike. 1974 Coast King Cruiser w/ banana seat and 66cc flying horse. Chain broke once on first 30 feet of ride. Messed with the alignment and made sure the masterlink was on right. Drove a block and broke again. Havent touched the bike in a year. Sitting in the garage. Need to try to get it running properly.

    Would the clutch have anything to do with the chain breaking? Maybe if it was locking up? Also, how does one adjust the clutch? i.e. and I dont mean adjusting the clutch cable.

    Any help would be much appreciated! Thanks!
  10. butre

    butre Well-Known Member

    If you're breaking chains more than once every couple hundred miles, your alignment is bad, your chain is too loose, or your chain is too tight.