chain falls off on fat tire bicycle

Discussion in '4-Stroke Engines' started by Jerry SantaMaria, Jun 13, 2016.

  1. Jerry SantaMaria

    Jerry SantaMaria New Member

    This is my second 4 stroke kit install. Both were purchased by spooky tooth cycles. For some reason I cannot get the chain to stay on this time. I purchased a fat tire mountain bike but no matter what I do I cannot keep the chain on the bike. I hope someone out there has experience with fat tire bikes and can help. I can get pics if needed.

    Jerry
     

  2. Jburr36

    Jburr36 Guest

    Does this mountain bike have rear suspension? If so it will cause oscillation like slack and tightness in the chain which was causing my sprocket to warp and flex. And when it did that the chain easily derailed off of it.

    The way I fixed this is to replace the chain tensioner like this: http://www.niagaracycle.com/categories/eclypse-single-guy-bicycle-chain-tensioner-mt-95c to absorb the oscillation. I mounted it as close to the sprocket as I could. Keep note that the 415 chain is heavier than the normal bike chain so it might be necessary to use another mid way between the sprocket and the engine due to the weight of the chain.
     
  3. bakaneko

    bakaneko Active Member

    I think it is due to your drive sprocket and rear wheel sprocket alignment due to the fat tire bike. I have a similar issue my bike is small so I have an imperfect tilt to the motor at about 5-10 degrees. What it does is make the chain twist slightly and want to jump off the drive sprocket. For irregular builds, we have to juggle possible alignment to two sprockets versus one (rear). I have a chain tensioner both at the drive sprocket and rear sprocket to compensate the imperfect tilt. It works great but ideally you would want to check your alignment and try to fix it and not use two tensioners to fix the imperfection. The top chain has tension and usually is fine, its the bottom chain right at the rear sprocket where most of the problem comes from. If you cannot get the imperfection hammered out and the chain is jumping from the rear sprocket, then place the chain tensioner as close to the rear sprocket as possible and the roller as low as possible. This will provide the best guide to the sprocket. again, ideally you fix the imperfection but u can always brute force it with two tensioners. see pic

    ** that nice brutalization of English...
     

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    Last edited: Jun 13, 2016
    Tom from Rubicon likes this.
  4. Jerry SantaMaria

    Jerry SantaMaria New Member

    The bike does not have rear suspension. I do want to say thank to all that did reply with advice and very helpful information. I will try 1 and then 2 chain tensioners if needed. Just to be correct the rear needs the tensioner on the bottom right?
     
  5. bakaneko

    bakaneko Active Member

    I also wanted to add that it does depend on your bike bar width. Some bikes have a very narrow bar closer to the axle. So, if there is not enough of a bar to properly grip the bar then move it further away from the axle. If you move it further away, I actually like to put the roller on top of the chain and then move the tensioner along the bar to provide tension. Finally, lining up the chain so that the links fall in the middle of the teeth of the rear sprocket when the bike is up right (not resting on a kick stand).

    Try one tensioner on the back and then finding an isolated road and slowly picking up speed and looking at the drive train. If it falls off again, you want to know where the problem is either the drive sprocket or rear sprocket. Hope that helps.
     

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  6. Jerry SantaMaria

    Jerry SantaMaria New Member

    This helps greatly.
     
  7. Legwon

    Legwon New Member

    being a fat tire bike, you will need to put the chain out with a jackshaft type system, to clear the tire. otherwise the chain will be on an angle and will fall off, no matter HOW many tensioners you have on it.
     
    Tom from Rubicon likes this.
  8. bakaneko

    bakaneko Active Member

    I am assuming that his setup does not have the chain rubbing against the tire because not only will you have chain alignment issues but the tire is going to have a flat soon. Depending on the angle, you can prevent the chain from falling off using chain tensioners. I have an imperfect 5-10 degree tilt and my chain does not fall off due to tensioners.
     
    Tom from Rubicon likes this.
  9. fattirejack

    fattirejack Member

    Legwon likes this.
  10. Frankfort MB's

    Frankfort MB's Well-Known Member

    Cool looking bike btw:D
     
  11. Frankenstein

    Frankenstein Active Member

  12. fattirejack

    fattirejack Member

    Yes it is. pipefitter, and millwright by trade.
     
  13. Frankenstein

    Frankenstein Active Member

    Nice, is that a stock Stingray frame modified, and where did the fork come. From?
     
  14. fattirejack

    fattirejack Member

    Mongoose Beast frame, modified. Front fork was built by me.
     
  15. Frankenstein

    Frankenstein Active Member

    You tilted the stem back? What welding method do you use?
     
  16. fattirejack

    fattirejack Member

    Mostly TIG, some MIG
     
  17. KCvale

    KCvale Motorized Bicycle Vendor

    Yes Jerry, pics would really help.

    The trick to motorizing a fat tire is to mount the engine where it fits best, and jackshaft the output to the right and into the bikes own pedal system, it is already designed to clear the fat tire, and you can use it's gears.

    Here are a 4-stroke, Electric and 2-stroke example of moving the power to the right side and using the pedal chain.

    [​IMG]

    [​IMG]

    [​IMG]

    Hope that helps ;-}
     
  18. bakaneko

    bakaneko Active Member

    You know the original poster seems to be fine. I am not sure why this thread is still going with comments... LOL :D
     
    Frankfort MB's likes this.
  19. KCvale

    KCvale Motorized Bicycle Vendor

    For me I was looking at recent posts and as usual if I have some insight I post a reply.
    It may not be needed by the OP now, but it should certainly help someone trying to motorize a fat tire bike in the future.
     
  20. Frankenstein

    Frankenstein Active Member

    Same, I've found useful information in threads as old as 1997 on the internet. Beyond a doubt people will eventually come back to this thread for information they need when they need it, it's not even a matter of if.
     
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