Crank too narrow!

Discussion in 'Bicycle Repair' started by Poby, Aug 20, 2008.

  1. Poby

    Poby New Member

    I just got my first motor, chinese 2-stroke, and I test fitted everything on my bike (a '68 schwinn racer single speed) and everything fits flawlessly. Everything, except the motor :-/

    The pedal crank is too narrow. The crank hits the sides of the motor, so it can't pedal at all. Is there anything that can be done? I just replaced the crank in question about a month ago when the old original broke while i was riding it. Since it's old, it was kinda hard to find the right crank for it, so I'm not sure if I can just go out and ask for a wider one, and I don't even really want to replace the part I just replaced.

    Anyways, any suggestions?
     

  2. meatwad

    meatwad Member

    Well it gets tricky. All the schwinn cranks I've come across are narrow. Could be that some of the fatter tire or stingray cranks are wide enough.

    The problem is that Schwinn uses 26 threads per inch on the crank vs the more common 24 , one less bearing and cups with a different outside diameter.

    I have found cups that will fit but you have to have a large pile of junk to find them.

    Your best bet is to google a set of cranks that are 26 thread per inch.

    Hopefully their width ( q factor) will be enough.

    Either that or get a 24 threads per inch assembly and a hammer and do naugty things to your frames bottom bracket tube.

    Whatever you do don't apply heat to the crank and fix it that way (cause I know someone is going to suggest that)
     
  3. Try this:

    [​IMG][​IMG]

    cutting the pedal, then welding a 45 degree bit onto it :)
     

    Attached Files:

  4. V 35

    V 35 Member

    That's one wild solution to a vexing problem, looks cool too,
    thanks for sharing your idea
     
  5. motorpsycho

    motorpsycho Active Member

    here's an option that may work.
    If you don't mind what kind of cranks the bike ends up with, you can buy these cheap and they come with EVERYTHING except a sprocket.
    yes, they are bmx, 3 peice cranks, but the point is that they MIGHT end up being wider than the cranks you have now. these come with cups, bearings, the spindle, and all necessary bolts. I put a set on my bmx bike to replace the steel one peice cranks that were on it, and these are MUCH nicer than the stock ones.
    the cool thing about these cranks is that a standard one peice crank sprocket will fit on them, and the kit comes with adapters for sprockets that have different size center holes.
    what i'm thinking is that maybe your stock cranks are narrower than these, and maybe the spindle on these is wider, which will set the crank arms out further?
    http://www.danscomp.com/products-PARTS-CRANKS/451053/Poverty_Carmi_Cranks.html

    the other option is the off set cranks sold on e-bay.
    these cranks for example are wider on both sides, but they are 3 peice cranks. I also think that the price is for ONE crank arm, not a set. it doesn;t actually say that, but if you read the description, it cleverly says "wider crank ARM" (not arms).
    http://www.ebay.com/itm/bicycle-Mot...Cycling_Parts_Accessories&hash=item27bac246a1

    these are one peice cranks, but i think only the left side crank arm is wider (to clear a pull starter).
    http://www.ebay.com/itm/bicycle-Mot...847?pt=LH_DefaultDomain_0&hash=item256c0e8cdf
     
    Last edited: Mar 25, 2012
  6. V 35

    V 35 Member

    Photos can be misleading, the ' wider ' crank looks like too big
    a sprocket for motorbike use, the lower the engine, the better the handling. The ' wide crank ' kit looks offset, that's so pedal sprocket lines up with coaster brake sprocket. In some cases, the engine could be offset left, to clear right crank arm. Most times this setup solves both problems, the BMX crank looks
    like a winner, the arms could be cut, drilled, tapped, for a short throw crank = more ground clearance . Thanks for the ideas.
     
  7. Big Red

    Big Red Active Member

    Pull Start

    Yeah V, The pull start has always been a problem with standard cranks on these. I haven't had to deal with one yet, Thank God. With the pull assembly and the wide crank ya gotta buy it also adds another $60 or $80 to your cost. It's a good idea if you have the extra money. These bikes are too easy to peddle start for me to spend the money. When I win the lotto I'll put pull starts on all my bikes.
    Big Red.
     
  8. WisdomWarlord

    WisdomWarlord New Member

    I am going to need a similar solution when I install my Honda GX110,, with pull start, on my bike. How has your bottom bracket held up? Has anything bent or wore out prematurely because of the extra bending forces caused by widening it like that?

    Thanks
    Jabez
     
  9. Haymaker21

    Haymaker21 New Member

    Oh man! This is exactly what i want to do for my bike! Does it matter what kind of metal my cranks are?
     
  10. V 35

    V 35 Member

    Yes, some mild steel parts weld beautifully, exotic alloy parts will defy welding, filler metal must be same as part being welded.

    The Motorbike philosophy is low end parts bend, high end parts break.
     
Loading...