Some help needed.

Discussion in 'Performance Mods' started by 32motleycrue, Nov 28, 2007.

  1. 32motleycrue

    32motleycrue Guest

    I picked up a 4hp Robin 2 Stroke Engine. Its made for a cement mixer so its got the 6:1 Gear box on it.

    How would I go about running it since now the axle spins 6 times slower than before?

    This is what I thought and I want to know if it works.

    Putting a 40t sprocket on the axle, running it to a 10t jackshaft, then back to a 40t rear wheel.
    In my head this works, but i'm a better frame builder than engine guy.

    Also, I would have to post a picture for this, but when I took the engine apart to clean it up I took off the throttle bit w/ governor and now im not that sure how it goes back on. If there are any diagrams out there, that would be sweet.

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  2. gone_fishin

    gone_fishin Guest

    that's a pretty neat double-tensioner idea...i moved this into "wild in the streets" because, well, it's wild :shock:

    i'm not much help with gearing, but you may count on a crazy or two coming along and helping out :)
    "....Get a bicycle. You will not regret it. If you live." - Mark Twain
    Last edited by a moderator: Dec 15, 2015
  3. 32motleycrue

    32motleycrue Guest

    Here is the bike its going on. No pedals. How would I go about making it just idle and not take off once I start the engine?
    The motor has the internal gear w/ clutch I think, but I know poop about motors.

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  4. mickey

    mickey Guest

    If you're going from 40 x 10 x 40, isn't that the same as 40 x 40? or 10 x 10? You'll just end up with 6:1 reduction. Is the jackstaff just to move power to the other side?
  5. gone_fishin

    gone_fishin Guest

    we need pics (or links) of the engine, too, before we can get to work :)

    i believe the jackshaft also serves to offset the power around the engine and back into center for transfer to the rear wheel.
  6. 32motleycrue

    32motleycrue Guest

    I'll put up pictures later tonight of the engine. Im at work all day so i'll just surf this site and look at cool bikes for now.
  7. Ghost0

    Ghost0 Guest

    The way your picture shows it would be 1:1. You are going 1:4 then back to 4:1 making it 1:1, effectively no change in ratio.

    If your engine has a clutch on it already you shouldn't have a problem with it sitting and idling after start up.
  8. 32motleycrue

    32motleycrue Guest

    Well currently its 6:1, how would I go about adjusting it so I can power the rear wheel and go about 40mph max? (20" rear)
  9. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:I'm a "crazy", and proud OF it.

    Tell me at what rpm your maximum hp and torque is realized. Then I can predict which gears you need to reach 40mph.

  10. Bean Oil

    Bean Oil Guest

    ^ MyRHONE (Myron) is the man... LOL... although if the op may not have those torque/rpm specs they might be published somewhere.

    I used to do gear-inch charts for friends when I rode mountain bikes, but I've forgotten all that stuff now. *sigh* With 7-speed clusters and three chainwheels there was a lot of cross-shifting involved if one wanted the very next possible ratio up or down... but I digress.

    Carry on. :)~
    Last edited by a moderator: Nov 28, 2007
  11. Dockspa1

    Dockspa1 Guest

    Ain't nobody like 5-7 to set you on the correct path when it comes to ratios.
    Your an asset to this villiage, 5-7! Thanks!
  12. jpilot

    jpilot Guest

  13. 32motleycrue

    32motleycrue Guest

    How would I find that out?
    I know its a 4 HP, but how can I find max torque?
  14. gone_fishin

    gone_fishin Guest

    when you get home, find anything anywhere (numbers, etc) on the engine. along with that and the pics you're gonna give us, someone will be able to help figure things out...kind of an impasse until tonite, but as you can tell people are waiting to help :)

    if you want, MBc can give you a note for the boss so you can leave early ;)
    "....Get a bicycle. You will not regret it. If you live." — Mark Twain
  15. 32motleycrue

    32motleycrue Guest

    2 more questions

    Ive built many chopper pedal bikes. I'm good with fabrication, but im terrible with engines and know little about them, so maybe you guys can help?

    Why do alot of your bikes have both an engine and pedals/cranks? Is it for legal purposes or how would that start the engine?

    What would you need to drop an engine into a frame and get it to go. How does it not just take off when you start the engine?

  16. ibdennyak

    ibdennyak Guest

  17. gone_fishin

    gone_fishin Guest

    because, "officially", a MotoredBike is a fully functioning bicycle with engine- or motor-assist on it. there is a legal classification (see "laws & legislation" forum) for this type of vehicle, tho the specifics vary from state to state.

    with a 6hp engine, there really isn't a legal issue, whether it pedals or not.

    if there's a centifugal clutch anywhere in the drive-train, you can forget about pop-starts.
  18. Alaskavan

    Alaskavan Guest

    Dug3x3 is a Robin dealer. He can probly find the rpm hp/torque info.
  19. 32motleycrue

    32motleycrue Guest

    Well I got about another 2 and a half hours before I get home. Once I do that i'm going to fab a motor mount, build up my springer fork, put the engine on the frame and take a lot of pics. So expect a bunch by like 9 pm EST.
  20. 32motleycrue

    32motleycrue Guest

    Well these are the pics. There werent any markings on it except for a sticker that said robin and then E then a 1. It was beat up so thats all I saw, then another small beat up one that said 4 HP/5200 I think.

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