Utilizing the derailleur gear system?

Discussion in 'General Questions' started by 86BG, Sep 21, 2008.

  1. 86BG

    86BG Member

    I've searched the forum -

    I finally got a 49cc engine free from a friend and was wondering if anyone here has ran a drive chain down onto the opposite side of the crank with a sprocket and removed the pedals? with a centrifugal clutch you could simply let off the throttle for a second or two, then shift gear, then apply throttle slowly to let the chain fall into place.

    I don't see why it wouldn't work as the problem would be too much torque to the chain when the chain is falling into the next gear, but that's eliminated with a clutch.

    You can keep your bike in the power band and get much more torque out of these small engines.. I don't see why EVERYONE isn't doing this. It's a free gearbox!

    What is your experiences?

  2. Mountainman

    Mountainman Active Member

    yes -- it should work

    easing up on drive pressure at times of changing gears

    I think that it will be tricky -- not tearing gears ect up

    let us know -- if you take on the project -- and how it works

    Ride That Thing - Mountainman
  3. 86BG

    86BG Member

    Yes I am taking on the project. I just tore the 49cc off the kid's sit down scooter that was messed up at the frame, so I know the engine outlasted the scooter. It's in pretty good condition and has good compresssion.

    The problem I am having now is that this engine was on a scooter with a 12v battery for the turn signals, horn, and headlight, and taillight and there's a terminal on the coil next to the pull start and a 2 terminal connector coming off the spark plug area. I think the connector coming from the spark plug area is for the kill switch and the other terminal on the coil is for charging the little 7AH battery.

    Also, this engine seems to have a sort of wet bath clutch looking housing coming off the shaft. Can anyone confirm this? I know it is a sort of clutch because sprocket doesn't spin when cranking
  4. ZnsaneRyder

    ZnsaneRyder Member

    My brother is making a bike-trailer out of a bike frame, but wants to do similar to what you are. One thing were trying to figure out is if there's enough torque, and if the gear ratio will be low enough on the low gears, so you can take advantage of the higher gears while shifting.
  5. 86BG

    86BG Member

    I fired up the 49cc today and it idles PERFECT and spins up to full RPM very smoothly. Best part - I pulled it from the scooter frame and the twist grip works flawless. I was planning on it not working and cleaning the carb but I guess the leftover gas kept the carb clean the year or more that it was sitting. I can also salvage the blinker relay and switches from the scooter and use them on the bike.

    I have a mountain bike with shocks in my shed that's in flawless condition and I plan on using it. I will work as hard as I can to get this done while I wait for my next check on the 1st to come in and go buy the 250cc twin cylinder 5-speed honda motorcycle engine for my homemade 2 seater full suspensioned buggy.

    ZnsaneRyder -

    For every time you half the gear ratio you get twice the torque from the engine, so lower gears are a good thing. Gear the last gear at the max RPM so that it reaches maybe 50. The lower you gear it the more torque you get. It will easily outdo the kits with a single gear in acceleration and speed. Use a gear ratio calculator at a go kart website to get it all right.

    If you want to alter the gear ratio a great deal you can make a small jackshaft with a go kart jackshaft kit or 2 small pillow blocks and a piece of axle or pipe.

    If anyone has some real experience with this method be sure to let me know how well it works. Also, is it still legal to drive the bike on the roads if I remove the pedals?
    Last edited: Sep 21, 2008
  6. Deraleur transmission

    With a recoil starter, it might work but if you eliminate the peddles, all you have is a MO. Would it still fall into the "with peddles, not over 30 mph" law? Maybe it is different than Oklahoma. Keith (trackfodder)Williams:???: Nutz-misspelled derailleur and can't edit title
    Last edited: Sep 21, 2008
  7. 86BG

    86BG Member

    I live in alabama and a friend said as long as it's under 50cc it doesn't matter, but I think he's wrong.

    It looks like I'm going to have to remove the front casette and replace it with a small sprocket for this to work.
    Last edited: Sep 22, 2008
  8. s_beaudry

    s_beaudry Member

    How are you going to mount it to the frame?

    Any pictures of the project yet?
  9. Ghost0

    Ghost0 Guest

  10. Actually try this for exactly what you're talking about.
  11. HoughMade

    HoughMade Guest

    Only you can keep the pedals- better yet!
  12. 86BG

    86BG Member

    Pictures when I get started.

    I pulled the engine mount plate off the scooter and am going to simply weld a tube under the plate and to the frame but make the mount tube pivot up and down for chain tensioning.

    I don't have any pictures yet but it seems the only way to do it with the gearing I want is with a jackshaft.

    The shaft comes out ont he right side of my engine, so I'm going to run a chain from the right side of the engine to a 48t 35pitch sprocket on the jackshaft, then on the left side of the jackshaft have an 11t 35pitch sprocket running down to the left side bike crank, which will have an 48t 35 pitch sprocket on it, then on the opposite side I'm going to have the smallest possible sized bike sprocket I can find on the right side of the crank in place of the casette.

    Lots of extra BS to do, I know, but it's worth it when first gear 6000 RPM is at 10 MPH, 2nd gear 6000 RPM at 20, and so on
    What are your thoughts?

    Does anyone know if there's a sprocket and chain pitch NUMBER that matches a standard bike chain?
    Last edited: Sep 22, 2008
  13. 86BG

    86BG Member

    second thought, without altering the casette, I could run an 11t from the engine to a 30t on the jackshaft, then on the other end of the jackshaft another 11t, then down to a 30t on the left side of the bicycle crank. my first gear shift should be at 10mph without altering anything on the bike besides removing the pedals.

    I don't see why removing the pedals is such a problem. Does it make the bike illegal?
  14. Mountainman

    Mountainman Active Member

    well - it would not be a motorized bicycle without pedals
    that's for sure...

    not sure if it would be legal or not --
    maybe called a -- motor driven cycle ?

    Ride That Thing - Mountainman
    Last edited: Sep 22, 2008
  15. kerf

    kerf Guest

    You are right, your friend is wrong.
  16. 86BG

    86BG Member

    I don't plan on ever using the pedals, so I can probably come up with a method to make it pedal powered on a seperate crank with a sprocket on the left side of the wheel.

    I just bought 2 30t and 3 11t 35 pitch sprockets and some chain for 30 bucks and I should have it done a few hours after I find a bike to put it on. The 2 I have are swingarm rear with shock/spring in the middle of the frame so unless I make one of them hardtail I'm going to have to find another bike. I could always mount the shock elsewhere, though.

    Now where can I find a tiny catalytic converter?

    Has anyone used electrical conduit for exhaust?

    Since it is categorized as a bicycle, is it legal to drive drunk? :) :)
    Last edited: Sep 22, 2008
  17. JE

    JE Guest

    UH why would you want to drive drunk and potentially hurt somone or you're self. Why not just poney up the $199 and buy exactly what you're talking about building from sickbikeparts.com
  18. 86BG

    86BG Member

    Have you ever ridden a bike drunk? The point IS to get hurt.

    Because 199 bucks is more expensive than 30 bucks and bolting stuff on is not how I like to do things.

    For example -

    Attached Files:

  19. moonlightspecial

    moonlightspecial New Member

  20. 86BG

    86BG Member

    Is this community built on consumerism or ingenuity? I can get the same result for the 30 bucks I spent, and use the money I saved, so can we stop pressing products on me through personal messages and this thread?

    I like to support a good product when I see one, and it is great, but 200$ is way overpriced.
    Last edited: Sep 22, 2008