I am having an issue with a 26 inch Beach Cruiser.

Everything was put together by a bike shop however one of the chains slipped off the sprocket during transport home. When I went to put it back on, which should have been easy (flip the bike on its handle bars and reattach the chain by taking off the back wheel and pulling it backward further into the rear dropouts to apply tension to the chain).

As a precaution I test pedaled it while it was still upside down the chain still slipped off.

I'm pretty sure the bike kit came with a second chain tensioner and for some reason I don't have it, probably due to bike shop error. If anyone can confirm that these kits come with two, I'd appreciate it. I hate to think I'm missing a part when I'm actually not.

Side note: The bike is also motorized, I don't know if that was a needed piece of information or not.

My question is, how do I get the chain to stay on when I pedal?

  • Motorized is quite important -- regular bicycles only have one chain. Can you get a manual or something for the kit?
    – Batman
    May 26, 2016 at 20:26
  • What kind of motor ? Petrol ones tend not to run backwards very well unless there's a freewheel mechanism. Is it the motor chain or the pedal chain ?
    – Criggie
    May 26, 2016 at 22:59
  • 1
    The design of such bikes varies all over the place. You need to provide a picture, at the very least. May 27, 2016 at 1:45
  • Batman, I have a manual. For both the bike and the motor. Essentially what it was was an ebay purchase from a Bike shop in AZ that consisted of a walmart-type bike and a motor, carborator etc. May 27, 2016 at 6:28
  • Criggie, Not sure, the box the motor came in had plenty of asian-style newspaper in it. May 27, 2016 at 6:28

2 Answers 2


Figured out the issue. The cotter pin behind the sprocket needed to be removed and the sprocket moved backwards.

Edit: that did not fix the issue. I'm still working on it.

  • It's good that you figured it out, and great that you posted your own answer. It would help others more if you add a picture or more explanation, to make it clearer what you mean by and the sprocket moved backwards.
    – andy256
    May 28, 2016 at 6:10

Check every link in the chain for stiff links, these can easily cause it to jump sprockets, if you find any use a chain splitting tool to slacken off the tight pin/pins.

If it's not stiff links, the chain/sprockets could be either loose, badly stretched or out of alignment. A worn stretched chain or sprockets will cause such issues.. If a new chain or sprocket are replaced separately they will not mesh together properly, both chain and sprockets must be replaced together to avoid jumping issues.

Also.. Look along the length of the affected chain to check that it looks in-line with the sprockets, it should be in-line an not skewed. Also make sure that when tension is applied through the chain via either motor or pedaling force, nothing is moving and forcing the chain to be out of line. Loose bearings, motor, crank etc

  • Good first answer - welcome to the site. Motorised bicycles are on topic as far as bicycle bits go, so your answer does address exactly that. +1
    – Criggie
    May 27, 2016 at 7:23

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