Where is the freewheel on Jackshaft kits? Recommendations?

Discussion in 'Motorized Bicycle General Discussion' started by Nehmo, Sep 20, 2017.

  1. Nehmo

    Nehmo Member

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    I assembled an m-bike with a 44-tooth rag joint rear sprocket. I thought I did a meticulous job installing the sprocket. (I did choose dish inward instead of dish outward. I went with a recommendation, but I believe I shouldn't have now.) The tensioner (attaching as a cantilever to the chainstay) is poorly engineered too, but I used it.
    After just a few miles, the machine threw the drive chain. I wasn't on the bike, but the report is that it occurred during breaking, which makes sense.
    Enough background. I don't like the existing drivetrain arrangement. For improvement, I could get a hub clamp rear sprocket holder, a better tensioner, or I could use a jackshaft kit.

    I like the concept of a jackshaft with a freewheel from the chain to the peddle cranks. Is that how these jackshaft kits are configured?
    Which jackshaft kit is considered good? (The reviews seem to say they are all terrible.)
    Where is a good description of one of these kits? (The places that offer them don't know how to write, apparently.)
    [​IMG]
     
  2. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    The answer to the question in your title is.....

    The freewheel in the picture is
    the bronze-colored round contraption with
    5 mounting holes and a large hole in the center.

    Since you did not mention how
    you intend to ride your bike,
    this is how I'd gear my bike:

    17t on the left-side jackshaft;
    10t on the right-side jackshaft;
    45t on the outer chainring;
    24t on the inner chainring.

    34t-14t on the rear cassette.
    Final drive will be equivalent to
    a 35t rear wheel sprocket.

    This is SBP's shift kit:
    http://sickbikeparts.com/2-stroke-hd-or-uhd-shifter-kit/
     
  3. Nehmo

    Nehmo Member

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    $240. USD, wow! Where is the $ in that pile of parts? I bought a new TaoTao 50cc scooter for $550 including shipping a couple of years ago to give a comparison. Anyway, I suppose that's the way it is. If I don't like the price, I should put one together myself. And I don't know how to do that.

    I'm using a 4-stroke 49cc. You linked to a shift kit that seems to be for a 2-stroke. I'm not sure if there is a difference. Is there?

    I want a low gear ratio. The original 44-tooth rear sprocket probably gives a ratio that I would like to duplicate. I don't have enough experience with the bike to know what ratio is appropriate, but I'm not a speed demon.

    I already have the pedal cranks that suit the engine. That's already assembled. Is there some reason these shift kids come with cranks?

    Is there some way to get a cheaper kit that doesn't include cranks?

    Did you buy and install the Sick Bike Parts shift kit?
     
  4. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

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    Scroll down on that link to see the 4-stroke kit for $190.
    You're right. It's expensive.
    I was lucky.
    I have a different engine. I didn't need the whole kit, only the pedal arms, 3-piece bottom bracket, freewheel, 3 sprockets & extra chain.
    The wider bottom bracket is to space out the outer chainring. This is so that the chainring aligns with the jackshaft sprocket.
     
  5. Pablo

    Pablo Master Bike Builder & Forum Sponsor

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    First of all, that pile of parts above in the picture is not a Sick Bike Parts kit. It's a cheap Chinese thing. Plenty of problems. We do have a much higher quality equivalent and it's under $150.

    http://sickbikeparts.com/standard-2-stroke-shifter-kit/

    The link in the above post, to answer your question, the cost driver is the Heavy Duty front freewheel itself.

    But you need a 4 Stroke kit: http://sickbikeparts.com/4-stroke-shift-kit/

    As for no cranks, the freewheel threads on the right crank for the 2 stroke kit - BUT on the 4 stroke kit you won't need threaded cranks, because we use a machined adapter, so we could leave them out - and take some cost out. Contact us if interested.

    Thanks!
     
    #5 Pablo, Sep 24, 2017
    Last edited: Sep 24, 2017
  6. KCvale

    KCvale Active Member

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    Yes, it allows your pedal chain rings to spin independent of the pedals.
    The key component is the freewheel bearing itself.

    You can't pedal up and start your bike, you have to start it with just your pedals.

    If you have a high compression 2-stroke you will want the HD bearing.
    For a 4 stroke with a pull start, the least expensive will work fine as it has it's own way to start.

    Sick Bike Parts kits hands down.
    http://sickbikeparts.com/shift-kit-and-all-drive-products/

    I've built over 50 shifters using their kits and they know their stuff.
    http://kcsbikes.com/KCsBuilds.asp?motor=All&shifter=Yes

    Gears change everything ;-}
     
  7. Nehmo

    Nehmo Member

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    That's a strong endorsement. And you've convinced me. It now seems like the only way to go. I have to get a jackshaft kit, and I also need to get gears at the rear hub. I could do that with a common derailer arrangement, or I could use a 3-speed hub, which (I think) I would prefer.

    You have made a business out of your devotion. I hadn't planned to get that involved. It seems motorized bikes are so attention demanding, getting really involved is necessary. And if you get really involved, (unless you are well funded by other means) making the activity a business can support the activity.

    Regarding your numerous builds. You have 3-wheelers, but I didn't see any tadpoles. Don't you like them?
     
  8. KCvale

    KCvale Active Member

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    Never tried one.

    If it's in your budget go with an Internal shifting hub.
    That way you always have a dead straight chain line to the rear wheel sprocket.

    I find a simple low cost 3-speed is fine for most everyone as long as you don't count on the coaster brake, back pedaling just spins.
    You are riding a shifter now, beef up you brakes.

    I can't help post this 53cc 4-stroke to a NuVinice CVT disc brake up.

    [​IMG]

    It don't take much power to both start fast, and go fast, with gears.

    Hope that helps
     
  9. Nehmo

    Nehmo Member

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    It's obvious a multi-ratio transmission of some sort is the solution. The derailer system is ingenious, I grant, but it's not really reliable. Do you recommend a particular 3-speed hub? And from which vendor?
     
  10. KCvale

    KCvale Active Member

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    Most of the low end IG hubs have a coaster brake, this rendered useless by the free cranks so look for one with an alternative rear brake, Shimino has a band brake 3-speed.

    Though I find 3 gears to be enough, so of better hubs have 5 over 8 like this build with an 8-speed Sturmey Archer internally geared rear hub.

    [​IMG]

    This build got an SA 3 speed disc brake hub.

    [​IMG]

    I personally like the SA 5-speed disc hub.
     
  11. joelnotroll

    joelnotroll Member

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    I felt an extreme sense of buyers remorse after getting the HD shift kit.
     
  12. KCvale

    KCvale Active Member

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    Why?
     
  13. joelnotroll

    joelnotroll Member

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    For the price I expected more. I was using it on my GT LTS to solve the issue of rear suspension(I know you know about an LTS and using a shift kit). I bought the Sickbikeparts HD shift kit.

    Its been years since I installed and used it so my memory is a bit fuzzy, but I believe the spacers to space the engine away from the jack shaft bracket didnt space it properly to tighten the chain from the engine to the jack shaft. This was an easy fix, I cut up an aluminum can in the shape of the spacers and put in enough to have it spaced properly.

    The next issue was the clamps included with the kit. They were just exhaust clamps from NAPA auto parts or something. When purchasing the kit I thought I was buying a high quality kit, but these made me think I had just bought something thrown together by some random ebay seller. The exhaust clamps included in this kit are bare steel. I keep my bike inside and they still ended up rusting. Because I was using these on my aluminum frame, tightening them down caused my frame to dent. It would have been a lot nicer if they had been aluminum. It probably wouldn't have been that hard for Sickbikeparts to use some aluminum roll cage clamps for this kit, but it seems like they took the cheap way out. I know it was my fault for tightening(possibly over tightening) the clamps which led to my frame denting. But if the kit was listed as *Not recommended for aluminum frames* I probably wouldn't have bought it and wouldn't have dented my frame.

    By the way, I'm listing the issues as they arose as I installed the kit. After the clamp issue I assembled the crank set up and noticed that it had a wobble to it. I called up Sickbikeparts and they told me "oh yeah, thats just how they are." I was pretty let down by this. It again made me think this was some low quality chinese kit. The crank set up did work fine even though it did have that wobble to it.

    Then was the issue of the chain from the jack shaft to the crank chainring. When I initially set up the kit, the chain was a perfect length. But after my first ride it stretched to the point that it would fall off. With the halflink it was too short,and with the regular link it was too long. At the time Sickbikeparts didn't offer the pedal side tensioner, but now they do. So I was pretty disappointed again in this kit because I saw this as something that should have been included with the kit.

    Overall the kit is a good idea in theory. The thing I did like about it was how it made the bike a lot easier to pedal because of the freewheel. The thing I didn't like about the Sickbikeparts kit specifically was the quality. And if this is the "good" kit, I can only imagine how bad the chinese kits probably are.


    The kit may work well on a non suspension frame, especially if it is steel. But to the OP, you may still have issues with the chain falling off. Now if the kit were cheaper, I would recommend it. But for the price, I think its not worth it. If you have the ability, or know anyone that does, you'll be better off making your own kit.


    Here are some pictures of my bike when I had it set up. It was fun the few times it worked (before the chain stretched)
    [​IMG]
    [​IMG]
     
  14. KCvale

    KCvale Active Member

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    I thought you got a kit and was building now?

    The reason the kits cost so much is this the $80. freewheel

    [​IMG]
    Good parts aren't cheap.
     

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