Thing to do / know before getting a Jack Shaft

Discussion in 'Motorized Bicycle General Discussion' started by geoldr, Jul 18, 2011.

  1. geoldr

    geoldr New Member

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    Hey guys, so I've been working on my bike for a few weeks now, and when it works its great :D Now I would like to move on, and make the next big step. I would like to purchase the jack shaft kit from SBP.

    What are the things I should know before buying it?

    It says on the site to have a good derailur (spelling), and I'm not sure if mine is good. Also, will I have to replace the rear cassette gearing, or is the one I have default OK? I can take pictures, its a bike from about 10 years ago, its a MOTIV. I think that company is non existent now. I also have a 66/80 CC china HT engine.
     
  2. Al.Fisherman

    Al.Fisherman New Member

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    Have you seen this????
    These are the things that I do, I see that others such as the seals (which I've never had one go bad) mentioned. All these mods or replacements are most likely less then $50.00. Choose what works for you, ignore the rest, but here you have them.

    1. Unpack engine
    2. Check for any missing parts
    3. Remove head
    4. Mill head (flat glass and 230 (or finer) grit sand paper. Rub gasket surface to insure it is flat. Check the cylinder also.
    5. Tap cylinder stud holes to insure they are taped to the bottom.
    6. Discard all studs and nuts.
    7. Replace studs with Metric 8.8 (US Grade 5) Replace nuts with locking nuts. 8mm studs are either 1.0 or 1.25 thread, 6mm studs are 1.0 thread. 8mmX1.0 is not common, but I have 1 engine with them.
    8. Replace spark plug with a NGK or the like.

    9. Replace spark plug wire and boot (check with lawnmower supply) or rob from old lawnmower. Use wire core lead.
    10. Mount the engine properly, no gaps between the bike tubes and engine mounts.
    Engine Mounting pictures by Ron-Becker - Photobucket
    11. Torque 8mm to 150 to 200 INCH POUNDS
    12. Torque 6mm to 60-70 INCH POUNDS
    13. I install cylinder studs with lock tite, and let set overnight
    14. I coat the head gasket with Copper Kote
    15. May need to bend exhaust pipe for crank or frame clearance. Recommend using heat.
    16. Remove or cap magneto white wire off.
    17. Re solder blue wire on magneto.
    18. Make sure all wires have a good connection and use tape or better yet heat shrink.
    19. Hook up kill wires AFTER you get engine running.
    20. Try not to drill holes in the bike frame.
    21. Do away with the clutch cable routing; there are a number of options.
    Homemade Mods pictures by Ron-Becker - Photobucket
    If you want to make yourself, PM me and I’ll give you a material list.
    22. On my kit the rag joint had gauge (Metric) 8.8 bolts, If not replace them. I replaced the nuts with lock nuts.
    23. I sealed the wires coming from the magneto out of the engine with RTV.
    24. Place a “O” ring in the carburetor throat.
    25. Some say replace the axle with a better one. Never had a axle bend on me.
    26. For coaster brakes…Some say trim the cap, but I don't like it. ‪Bearing cap mod‬‏ - YouTube or a file of sorts can be used.
     
  3. Pycngryn

    Pycngryn New Member

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    My experience had been very troubled. After fixing "touching chain" issues with 3 spacer washers on the chainring posts and a washer on the Jack Shaft . 3 miles later the freewheel blows apart causing the chain to warp the small chainring, ruin the Jump Stop and the chain itself. The tool I ordered to remove the destroyed freewheel did not work and so I had to get new crank arms. 10 days and $140.00 later I am hoping to rebuild with extra plastic chain guards sandwiched on both sides of chain rings to prevent deraillments. Anybody else having these problems?
     
  4. donutguy

    donutguy New Member

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    I guess you have to look at the overall quality and type of bike. Wally World bikes typically use plastic as much as possible in their derailleurs, bottom brackets and rear hubs/freewheel.

    After all- they are designed for 1/2 horsepower max (human power) and most engines are putting out around 3 horsepower.....that's 6 times what is designed for, even good bike components won't take that abuse forever.
     
  5. geoldr

    geoldr New Member

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    I got my bike from Costco a while back. I'm not exactly sure what to ask, but it seems that I have mostly everything in check for install.

    Is it difficult to get the jack shaft installed?
     
  6. homejones

    homejones New Member

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    I haven't doe an install myself, but would really like to at some point. So I read through the install directions a few times on the SPB site. I highly recommend it. Seems like there are A LOT of steps involved. Would really love to do this in the future, but since I spent $60 on a custom hub adapter and sprocket set from manic mechanic, will probably hang onto my current setup for a while. Good luck.
     
  7. geoldr

    geoldr New Member

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    Yeah I also read the instructions. I think id be able to do it though.

    To anyone who has the jack shift kit from SBP, the gears only shift in the back?
    I found this on their site:
    Sick Bike Parts

    Would that fit my wheel? How do I know if I have a free body hub wheel?

    Also it says on the site

    "have a chromoly or quick release rear axle, standard steel axles will bend"

    What does that mean?
     
    #7 geoldr, Jul 19, 2011
    Last edited: Jul 19, 2011
  8. turbojoe

    turbojoe New Member

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    It means that you will have have to replace your standard steel axle on your rear to either a chromoly axle or a quick release axle that comes with most
    high end mountain bikes (not the ones from wally world). Otherwise, you will
    bend an axle and will have to replace your rear wheel. I put a SBP shiftkit on a Micargi Panther. I used the stock wheels and ended up bending the axle and hub. I had to replace the wheel and the guy I bought it from said that that axle would be fine but I ended up bending that one too. So I bought a chromoly axle and put that on the wheel.

    Another thing to consider is that your chain is aligned right and your derailleur is adjusted properly. The chain on my bike derailed and it destroyed my derailleur. I personally had a lot problems with the shift kit but I think that had a lot to do with the lack of quality of the bike that I put it on.

    [​IMG]
     
    #8 turbojoe, Jul 19, 2011
    Last edited: Jul 19, 2011
  9. geoldr

    geoldr New Member

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  10. turbojoe

    turbojoe New Member

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    The axle is the rod that goes through the center (the hub) of the wheel and rotates around. The part where you bolt the wheel to the frame.

    Here is the chromoly axle that I bought for my bike:
    Pyramid Rear Hub Axle 3/8x185mm 26 Thread Solid Chromoly | BikepartsUSA
     
  11. geoldr

    geoldr New Member

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    Oh ok. Do those fit on regular 26 inch wheels and is it hard to install? I never have taken apart my wheels before
     
  12. turbojoe

    turbojoe New Member

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    You will need a cone wrench in order to remove the cone bearings and a special tool to remove the freewheel/cassette. Remove the old axle being careful not to lose the bearings. Wipe off the old grease and apply new grease. put everything back together. Probably the easy way to do it is to take your wheel and new axle to your local bike shop and have them swap it out. Actually, you may want to check with your local bike shop to see if they carry chromoly axles. If they don't have them, then they can tell you what size you will need. A 26 inch wheel normally takes 3/8" diameter and whatever length depending on the freewheel/cassette size. I have a 7 speed so I got the 185mm but I probably could have used a 175mm axle.
     
  13. geoldr

    geoldr New Member

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  14. Pycngryn

    Pycngryn New Member

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    Update: During the front chainring and crank rebuild I discovered that I had intalled the Jump Stop Backwards. Most likley causing the catastrophic deraillments. Stupid Me! Using longer bolts and more spacers, adding another plastic chain guard to the inside of the large chain ring my SBP shift kit now works like a dream! That, in addition to adding a RT Performance carb from ThatDax, my bike is tearin' it up, up here at 8,000+ ft. dnut
     
  15. kevinkrg6

    kevinkrg6 New Member

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    Something tells me you should get a stronger chain that will still fit.

    If 415's are streching after use, your bike chain is definitely going to stretch.

    A jack shaft uses the original bike chain.
     

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