Problem with chain.

Discussion in 'Motorized Bicycle General Discussion' started by psprat496, Mar 17, 2010.

  1. psprat496

    psprat496 New Member

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    Ok well heres the problem. The chain on my bike seems to tighten and get loose when the bike moves. Instead of like a regular bike where the chain stays the same tension it gets really tight and then loose. At first I thought it was the sprocket but it doesn't seem to be that off and is actually pretty centered. I don't know why it does this and it's really annoying because whenever I hit a certain speed the chain starts vibrating like crazy and makes a very loud sound and the bike won't budge any higher from that speed. Anyone know if this is a common problem or if anything else could be causing thing?

    Also the sprocket isn't 100% centered but it is extremely close. Any ideas?
     
  2. exavid

    exavid New Member

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    It takes very little off center on the sprocket to make the chain go slack and tight. On my 2 stroke bike the tension goes from 1/4" slack to almost 3/4" as the wheel turns. There was very little off center when I put the wheel on the bike. I'll take it off eventually and get that sprocket right on the money but right now it's good enough. I think the thing might have shifted a bit in use which isn't impossible since it's only held by a rubber sandwich clamped to the spokes. If you have as much as 1/16" off center on the sprocket it's going to make a fairly large amount of change in chain tension as the sprocket is turned. That's a good argument for an idler pretty close to the sprocket. On my bike there's no idler so I keep a watch on the chain tension. I like running without an idler because it quiets the bike and makes it easier to pedal.
     
  3. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Extremely close may not be enough.

    Sometimes the center hole is drilled off center.

    If your chain is too tight, it will aggravate the problem.
     
  4. psprat496

    psprat496 New Member

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    Never knew that even 1/16 of an inch would distort the chain. Well I guess I'm going to take the wheel off tonight and try to center it up just right because it is very annoying hitting 26 and just have the chain start to scream and feel the bike jerking back and forth. Thanks for the help.
     
  5. exavid

    exavid New Member

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    It's pretty critical to get the sprocket centered. If it goes tight on part of the wheel rotation it's putting a pretty heavy load on the engine mounts and driving sprocket bearing. Effectively it's yanking on the engine each time the wheel turns over.
     
  6. psprat496

    psprat496 New Member

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    Now how do you get around mounting the sprocket? I mean I just spent 2 hours trying to even it all out and it did but not by a lot. The section of the chain leading into the engine still bounces around a lot. I really don't know what to do. I've seen how spooky tooth sells a wheel with the sprocket already mounted on there so I might just have to go for that. Do you know if anyone sells premounted wheels with sprocket already hooked up? I'd actually pay for someone to do this for me it's that frustrating.
     
  7. bairdco

    bairdco a guy who makes cool bikes

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    the chains will "bounce" around on all these engines. they're pretty jerky. it's just a matter of "how much."

    if your sprocket is a little off center, but not too loose as to derail the chain, and not too tight like it's trying to pull the engine off, just go with it.

    pretty much every bicycle chain has hi and low spots in them also. usually because of the force pedaling, it'll elongate the hole in the sprocket the crank sets in (on a one piece crank) or will tweak the actual sprockets with three piece cranksets. or if the sprocket isn't "true" side to side.

    also, when installing the wheel, you need to find the tightest spot in the chain when tightening it down. if you don't, when the wheel rotates to that spot, it's gonna be way too tight.
     
  8. Cabinfever1977

    Cabinfever1977 New Member

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    Ive always had that problem too, but i seem to have gotten it right this time, i spent more time centering my sprocket and its good and needs no adjustment.

    And what Bairdco said is true, when you tighten the chain, first find the part of the chain when its the tightest and tighten it til its too tight then loosen it a little, that way it will never be too tight.
     
  9. psprat496

    psprat496 New Member

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    Ok well after trying to line up the sprocket a bit it seems to have gotten a little better. I'll actually test it tomorrow and also try what you said about finding the tightest spot and tightening it when it's too tight and see how that works out. I was also thinking of a way to center up the sprocket 100%. If I could bring the wheel down to Home Depot and get a metal, or brass pipe that is just the right size as the hole in the sprocket that would ensure me that the entire sprocket is even. Going to try that this weekend. Let you know how it turns out.
     
  10. bairdco

    bairdco a guy who makes cool bikes

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    when i used the kit mounting crap, i'd get the sprocket snug, then put it on the bike and spin the wheel, holding a marker next to it to mark the hi and lo spots. then i'd tap on it with a rubber mallet at the hi spots.

    it's a pian, but it worked.

    now i just use sprocket adapters. it's much less aggravating.
     
  11. K.i.p

    K.i.p New Member

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    bairdco, yep. I used a marker to true my rims and verify the sprocket run out (actually lack of). I use this method quite frequently working with lathe set ups. Very sound advice.
     
  12. dag_29307

    dag_29307 New Member

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    how well did you inspect the chain? I had a similar problem with mine and come to find the chain roller was split in two. Thus causing the chain to catch the top of the tooth on the sprocket. Also check for "stretch in the links you may want to replace the chain.
     
  13. psprat496

    psprat496 New Member

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    Well the chain tensioner is in really good shape and I just replaced the chain. I think I'm going to buy the mounting bracket that I've seen some guy around here sell and probably add a 36t sprocket to it to give me that much more speed.
     
  14. psprat496

    psprat496 New Member

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    And are those the sprocket adapters that are found here?

    http://motorbicycling.com/f3/top-hat-sprocket-adapter-2131.html

    How are they working out for you? Does it solve the problem and keep the chain the same tension all the way around?
     
  15. exavid

    exavid New Member

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    One thing that helps with the tensioner is to put a bit of twist in the mount to align the roller with the chain. Normally the chainstay isn't parallel with the chain which puts the tensioner roller at an angle to the chain. I think the tensioner assembly that uses two straps and four bolts to clamp on the bike instead of the one that uses only two bolts and one strap is less likely to move. The two straps allow the clamps to accomodate themselves better to the shape of the chainstay.
     
  16. Nougat

    Nougat New Member

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    He's not talking about the top hat. That'll get you rear disc brakes along with a sprocket. He's talking about the Manic Mechanic hub adapter, which clamps on around the hub, and then you bolt the sprocket to it, all in place of the rag joint.
     
  17. psprat496

    psprat496 New Member

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    Yep I pm'ed him and got some info on it. Also called up Manic Mechanic and got some more info. I'm going to buy a micrometer this weekend so I could make my measurements and place an order. Gonna get their adapters along with a 36t sprocket. Anyone know what kind of speeds I might be pushing (ball park estimate)? I got the stock 44t on there along with an sbp expansion chamber, and air filter. Topping out at around 34-36 now but after the sprocket swap?
     
  18. Nougat

    Nougat New Member

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    I'm gonna wildly guess 42-45.
     

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