Drive sprocket too large?

Discussion in 'General Questions' started by frostic, Feb 21, 2016.

  1. frostic

    frostic New Member

    Hello, I recently got an 80cc engine kit and put it on my cruiser bike.
    when i tryed to put the chain on i noticed that the drive sprocket DON'T fit the chain. it is a 415 chain and works on another motorized bike without issues. do i have to buy a new drive sprocket? why don't the chain fit? i can measure the tooth spacing with a measuring tape if someone needs to know the spacing and size of the teeth if needed. it seems like the 4th tooth the chain goes on it causes the 5th one to fall about 2mm shy and goes up over the sprocket and causes the chain to get stuck and jammed in the drive sprocket housing. any help would be appreciated.

  2. crassius

    crassius Well-Known Member

    often the drive sprocket is one that was stamped out flat rather than machined with pointy teeth - with a 415H chain, the rollers are a bit wider than regular 415 chain so one needs to file or grind the tips of the teeth a bit

    I've seen folks get away with putting chain on REALLY tight and riding carefully until the chain stretches some, but I always grind the teeth when I get one of those sprockets.
  3. frostic

    frostic New Member

    Thankyou for the reply Crassius. yea i started hand fileing the sprocket. this takes forever but its almost accepting the chain now. i took a break to reply lolol
  4. bigkev81

    bigkev81 Member

    I seem to be having the same issue. A 415 bike chain, purchased from my local motorized bike dealer.

    I have a dremel and can grind the teeth down.

    Do I grind them flat so it's shorter. Or at an angle to make it pointy.

    And do I grind all teeth. Or just the one I'm having problems with?

    Also how can I get the sprocket out so I can work on it?

  5. frostic

    frostic New Member

    i wouldnt make them shorter... and dont grind into a point. just follow the shape that is already there on the inside between the teeth. worked for me...
  6. frostic

    frostic New Member

    the red in this image is where you will want to dremel out all the way to the tip. you wont take off but a very small amount then all chain links will fit. just work slow till you can run the whole chain around on the sprocket
    this is the tip i used.

    Last edited: Aug 11, 2016
  7. agrmodz

    agrmodz Member

    If you can get it on, pedal it for a bit and it will wear-in, Happend to my santa fe 66cc motor..
  8. frostic

    frostic New Member

    you should have a sprocket puller in your engine kit. its black and there are tutorials but i dont suggest it. i did it with the sprocket still attached.
  9. frostic

    frostic New Member

    if you like breaking chains yes. however mine was really bad and needed alot of grinding down. if it is just a small bit sure but i wouldn't make the bike force the chain on as you can 1 break a chain, and 2 you can cause your sprocket to go out of alignment when it jams up the chain inside. i had both happen on seperate bike builds. he should dremel out the teeth to be safe...
  10. agrmodz

    agrmodz Member

    Your probably right, but i couldn't be stuffed with my build it was about as bad as the chain in that picture... I just stuck it on and went for a pedal.. lol about about 300m it was alot better, it still clicked on and off for the next few km but it did work out in the end..
  11. bigkev81

    bigkev81 Member

    Thanks for the info guys! I didn't get a sprocket puller as I bought my bike assembled already. But after seeing a youtube video by bikeberry, I did it with the sproket still attached.
    Now I got a new problem. The chain goes on the sprocket fine now, but the chain is TOO SHORT!!! WTF?

    I've removed the tensioner, but its still too short. If I have both ends sitting on wheel sprocket, it is short by 2 teeth. 1 tooth if I count the master link.

    What do I do? Do I need a longer chain? Or can I just add links from my old chain?
    I've tried removing some links from my old chain, but the cheap chain tool I bought from ebay is crap, and the pin never pushes the rivet through, as the chain seems to move on tightening. :(

    I'm starting to get really frustrated with this bike, lol, a new issue at every step.
  12. crassius

    crassius Well-Known Member

    don't usually see short chains - is it 110 links?, is motor bolted to seat stay with spacers at front mount for longer frames?

    one can grind or file pins down till a nail will push them thru to add links
  13. bigkev81

    bigkev81 Member

    Thats what I thought, the chain should be long enough.
    I don't know how many links the chain is. Heres a photo of how its mounted.

    I am pulling it as tight as I can but cannot pull it tight enough to close the chain. Even though there seems to be plenty of slack on the bottom when i have both ends resting on the wheel sprocket.
    Is there a trick to pulling the chain tighter?

    If I can tighten the chain by one more tooth, I can close it with my master link.

    I had a friend who used to do my work for me, and he has successfully used this exact chain before (ordered from the same place).

    If I can't figure it out, I will go to the bike store to buy a quality chain breaker so I can add links and close them onto my chain. I'd rather avoid spending the extra $ though as I am already way over budget on my project.
    Last edited: Aug 11, 2016
  14. frostic

    frostic New Member

    I had the chain length issue too. im dealing with it today actually LOL but its ok what seems to happen is some chains sent by a company from ebay seem to send short chains. what i suggest is getting a NEW chain because the ones that come with an engine kit are what i call a butter chain. they are thin and very bad. but you can look up KMC industrial chains. these are the highest quality. i order mine from a lady lynn. her site is

    KMC UNDUSTRIAL 415 SPEED CHAIN,upgraded but not as thick as the thick kit chains. Great when there are tire clearance issues. Pin Length 10.70mm,Link Height 9.83mm, 1/2 X 3/16. Works well on Maniac Mechanic Sprocket adapters.$14.00

    KMC 415

    Pitch - P 0.5 in

    Pin Length 0.421in 10.73mm

    Pin Diameter - D 0.143in 3.65mm

    Roller Width - W 0.191in 4.89mm

    Roller Diameter - R 0.304in 7.71mm

    Plate Height - H 0.387in 9.86mm

    Plate Thickness - T 0.044in 1.07mm

    Overall Width - F 0.209in

    Overall Width - G 0.213in

    Average Weight Per Foot 0.19lb

    Average Ultimate Strength 2,000lb

    Finish Carbon Steel

    NOTE: she is really sweet TALKATIVE woman. she has helped me with alot of issues i come by. she also sells alot better chain tentioners. like the spring loaded an arc tentioners. i know it might be pricy but that is what google is for. (search prices) :p
  15. bigkev81

    bigkev81 Member

    Thanks for the tip frostic.

    Unfortunately I can't find any dealers in Australia where I live and I want to get this bike up and running asap. (I planned to have it running Monday just past lol)
    I will order the KMC chain, but in the meantime will find some other solution.

    Anyways, I am gonna see if I can move my rear wheel forward a little bit to make the current chain fit. Not sure its doable on my bike but will give it a go.
  16. agrmodz

    agrmodz Member

    Thats an easy fix, you can....
    - move the back of the motor down more
    - move the back wheel of the bike in closer
    - get a smaller back sprocket
    - get a longer chain
    All should work if its only one link you need.
    bigkev81 likes this.
  17. frostic

    frostic New Member

    but remember 1 thing. dont try to run it without a chain tentioner. or the chain will pop off if the sprocket is not perfectly aligned so make sure you use a chain tentioner.
    it is not only to tention it but to align the chain also :)
  18. Frankfort MB's

    Frankfort MB's Well-Known Member

    Have to disagree here.
    It's better to NOT use tensioner because most tensioners don't work well, plus it's another thing to slow down the chain.....

    I recommend them if you have vertical dropouts because then you don't have a way to tighten the chain:)
  19. frostic

    frostic New Member

    Well i use the arch tensioner and weld it to the frame. and you should weld any tensioner on if you can get access to a welder. that makes it permanant and with the arch tentioner you can still adjust it. it has 2 contact points not like the others.
    [​IMG] 10" arch tensioner and the maniac mechanic sprocket seen here is the best setup i have found. the sprocket mounts to the HUB not the spokes. it is pricy but worth it... all my bike builds have this^^
  20. pghewins

    pghewins Member

    415 chain is a generic for the pitch 415 comes in 3 widths 415s the one you need a slim chain same as on aprillia and yamaha 50 cc or 415 or 415 h you have been sold a heavy duty wider chain which is fouling the casing do not ever ever ever file or grind your sprockets if the chain doesnt fit you have been sold a rolling chain ie industrial these engines dont need one and want fit file your sprocket it will last about 100 miles as you have taken all of the case hardening off it