A Different Mod....

Discussion in 'Transmission / Drivetrain' started by Lee Shelton, Dec 19, 2016.

  1. Lee Shelton

    Lee Shelton New Member

    Hi guys. I've been building my motorized build from the ground up...so to speak. I slapped a 79cc Predator on a 21-speed. I removed the crank, using the bottom bracket to build a jackshaft ( 5/8" shaft 9"L 5/8" presicion bearings [OD 1- 3/8"] meshed int the original ballbearings). NO PEDALING ALLOWED. All was going well until the last two steps - mounting the drive sprockets and drivetrain! Temporarily I wanted to power a gear mounted on the leftside rear wheel. Ultimately, I want to drive the bike gears. My problem is broken down into both short term and long term. The short term problem: The leftside 9 hole - 32 teeth, dished sprocket takes #415H chain but I can't find a 5/8" bore keyed sprocket to mount on the jackshaft.
    The long term problem: I can't find any sprocket to mount on the right side that fits the multi-speed bike chain. I need help!

  2. Street Ryderz

    Street Ryderz Well-Known Member

    Stanton inc. has all the gears you need for 5/8''keyed shaft both chain sizes!
  3. Lee Shelton

    Lee Shelton New Member

    Hey! Thanx!
  4. Street Ryderz

    Street Ryderz Well-Known Member

    glad to help! good luck!like to see it when done!
  5. FurryOnTheInside

    FurryOnTheInside Well-Known Member

  6. Frankenstein

    Frankenstein Well-Known Member

    Also you can turn down a gear on a keyed shaft to fit thinner chains, done it twice. Put the gear on a drive shaft of the right size and make it spin under motor power. Then run an angle grinder along the teeth and body of the gear untill the chain fits well. Take it very slow at first and lightly feel out the danger zone with the angles of contact you can make, some work nicely and others try to rip the grinder from your hand. That being said wear your damn goggles!
  7. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    I've heard of this technique in relation to the #415 engine output sprocket, but I think I also read an opinion that it will ruin the hardening and the sprocket will wear quickly.. what have you experienced?
  8. Frankenstein

    Frankenstein Well-Known Member

    No problems since I don't put the grinder in the teeth and ruin the hardness where the chain actually pulls. Just take it easy and don't burn the metal, took almost an hour last time to slowly run down and fit the chain we were using.
    FurryOnTheInside likes this.
  9. Frankenstein

    Frankenstein Well-Known Member

    Also had to use a belt sander on a sprocket to fit my nuvinci, was too thick a sprocket, if the metal doesn't get so hot you can't grab it for a moment then you aren't getting anywhere hot enough to destroy the temperament, it's like filing but slightly faster.
    FurryOnTheInside likes this.
  10. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    Yes I understand that you're only grinding the side, but heat spreads. I have just read this objection and not actually sure if I've read an actual account the experience, so I am just looking for real confirmation that it works well in practice. Have you put many miles on the thinned sprocket?
  11. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    Okay, you've convinced me. :)
  12. Frankenstein

    Frankenstein Well-Known Member

    Well we turned it over in the hot summer and now it's almost Christmas, his large sprocket is not even on the radar and the tension looked good last I saw a week ago when we were prepping to turn a THIRD sprocket over and I even happen to suggest it today because he was mentioning changing his gearing a little for more top end.

    I'm confident I could install it in my bike if I wanted and I'd have no problems, in fact I might need to since after 8 months mines beginning to look a bit more worn, could use a swap in a few months depending on how hard I use it. Lasting longer than the original did anyways so...
    FurryOnTheInside likes this.
  13. skyash

    skyash Active Member

    All my sprockets are turned down . And work fine .we heat hardened every thing at my work and the hard ness seems to penetrate at least 1 cm to even an inch into the steel .sometimes making it a real pain to cut a key way or drill set screw holes .all the ones in pic are turned down

    Attached Files:

  14. Frankenstein

    Frankenstein Well-Known Member

    Yeah that's perfect, I find that if you have a larger supply of fat bites you can turn them all down to what you eventually need chain wise.

    They last as long as any other, or as above if you can re treat the metal then you have a great option. Remember we are not looking for lighter bicycles exactly. We are trying to make something reliable, and the extra weight is certainly worth it in this area.
  15. 5-7HEAVEN

    5-7HEAVEN Active Member

    This 9-tooth sprocket will fit and be 4:1 gear ratio:

    Combined with a 48t rear sprocket, that'd be 5.33:1 ratio.

    If you want to drive the bike's gears, use these parts:



    This will chain to the rear cassette.
    You won't need a freewheel, 'cause you don't intend to pedal.

    For the left side, try this:

    and this:

    also this:

    Sadly, for either left or right-side chain drive,
    the gear ratios will still be numerically low.

    Methinks you'll need a torque converter along with
    the gears and sprockets to make this work.

    On this forum, there have been many ways how
    other members have done their install.

    Good luck.
    Last edited: Aug 20, 2017
  16. Frankenstein

    Frankenstein Well-Known Member

  17. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    I think the OP wanted to remove the pedals entirely. He must have a pull start.
    What's with all the zombie thread resurrection lately anyway? :p
    Incidentally I did have a go at making a kit 10t fit a #410 chain the other day and it went well I think. I will have no hesitation grinding it down even narrower to fit multi speed chain. :)
  18. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    I did it a similar but different way. I have a bench grinder and a small dremel-ish rotary tool, and I knocked the 10t engine sprocket onto a bamboo cane so I could rotate it easily and steadily, and not burn my fingers when using the bench grinder or chop them off when using the cutting disc on the rotary tool. :)