Jackshaft Shift Kit Questions for anyone thats allready installed one

Discussion in 'Transmission / Drivetrain' started by sactownie, Aug 2, 2013.

  1. sactownie

    sactownie Member

    Hi people. Doing my 1st install and have some questions maybe someone knows the answers?

    1. What size chain do you run on the engine to jackshaft sprocket?
    I'm trying to use 415 from the engine kit, It looks like its going to rub the jackshaft plate. The engine sprocket wont accept 410 bmx chain, my guess the sprocket to wide? if using 415 do you use extra washers to space the jackshaft sprocket further to the outside?

    2. Can you use a 1/2 link on the engine to jackshaft that has a tiny cotter pin without that link failing?

    3. What size sprocket do you have on the engine output? Mine has 10 teeth, my engine to jackshaft chain wouldn't fit with any combo of the included shims. After days scratching my head I milled the spacer down from 1/2 to about 3/8, took me about 3 hours last night with a piece of glass and sandpaper and now I have no problems fitting it, has anyone else had to do that?

    This is where I am at in my install as of tonight. I am taking my time trying to get it right the first time. This is my first motor bike too so the engine is brand new also.
     
    Last edited: Aug 5, 2013

  2. Fabian

    Fabian Well-Known Member

    You do not mill the spacer down.
    You file the part of the engine case where the spacer sits onto. This part of the engine is typically not flat, so it needs to filed down about 3mm to get it perfectly flat and square to the inner face of the clutch housing.

    Use the 415 chain supplied with the shift kit. It will not rub on the shift kit plate if the 17 tooth sprocket is lined up with the 10 tooth engine output shaft sprocket. The shims are included to give you the ability to get the alignment perfect.

    The 10 tooth engine output shaft sprocket is the only one that seems to be available.

    A good tip is to use glue (i used super glue) to attach a piece of 4mm (hard) rubber to the (standing from behind the bike) left hand side of the inner jackshaft plate, thereby allowing the plate to transfer twisting force directly to the seat post tube.
    If you do not make this small modification the twisting motion (especially if you are using the SickBikeParts optional high torque gearing) will pull the engine and jackshaft in a downwards arc which will cause chain alignment problems; either derailing the chain or punching out chain side plates.

    Do a Google search for:


    "Additional stability for the Sick Bike Parts shift kit"


    and


    "Chain Tensioner for 2-stroke engine and SickBikeParts (SBP, Sick Bikeparts) shift kit"


    and


    "Chain tensioner for chainwheel side of SickBikeParts (Sick Bike Parts SBP) shift kit"





    and this beneficial modification if you travel on rough surfaces:


    "Chain Stabilisation Device in conjunction with SickBikeParts, SBP, Sick Bike Parts, shift kit"
     
    Last edited: Aug 3, 2013
  3. sactownie

    sactownie Member

    Yea I filed the motor mount pad on the actual motor casing. It was already pretty flat to begin with. I cant see filing that down 3mm with the file I had, It would have been really uneven so I just milled the spacer. The SBP install manual shows a 11 or possible 12 tooth engine output sprocket on there install example. Thats why I thought maybe I have an uncommon sprocket that cause me not to be able to fit 15 links correctly.
    The shift kit comes with a 410 chain for the jackshaft to crank. I tried to fit that to the engine to jackshaft, the engine sprocket doesn't like it.
    I email the tech guy at sbp all these questions but didn't really get any answers.
    I'm not new to any of this tech stuff, Maybe a little rusty.
    There must be differences in the 80cc (66cc) engine kit I got from engines online shop why I had to modify this thing to fit. I just worry about that chain being to wide, I don't want it rubbing the jackshaft plate. If I could fit the 410 thinner chain it would be great but I guess I have to change that engine sprocket?
     
  4. Fabian

    Fabian Well-Known Member

    If the shift kit comes with a 410 chain, then fit the 410 chain.

    All of the Chinese Bicycle Engines are different, even from the same manufacturer - some of them can have seriously different (external) dimensional measurements.
    I have had to file down every one of my engine cases to get the mounting area flat and true.
    With a steady hand and a small (engineers) hand square and attention to accuracy you can get the engine to jackshaft mounting surface perfectly flat and true. On one occasion i spent 3 hours getting it perfect in all dimensions and for proper chain fit and a heck of a lot of material had to be filed away.

    The SickBikeParts sprockets (and optional sprockets) are "exclusively" for the right hand side of the Jackshaft kit, except for the 17 tooth left hand side sprocket.
     
  5. Ghost0

    Ghost0 New Member

    Fabian, thanks for all your help getting this customer good information. Just to clear up a point. All Chinese 2 strokes come with 10 tooth output sprockets and so that is what is shown in our instructions. As the instructions state we recommend using the chain that came with your engine kit for the left side chain and the 410 chain that came with the shift kit for the right side chain.

    As was noted not all engines are the same which is why we give some direction in the manual and shimming options with the kit. Typically what works is the 1/4 inch spacer with the two holes and the two 1/8 shims but sometimes a little material removal from the back of the engine is required and as Fabian said recommended to get proper mating and alignment. If you have any more questions feel free to contact me directly through our website.
     
  6. KCvale

    KCvale Motorized Bicycle Vendor

    Just wait a day or so, maybe even a week as it so much, for pics and tips.
    I have built a couple dozen JS builds 2 and 4 stroke and just doing another 2-stroke now and taking pics and notes for a new assembly guide for my shop.

    It is an art bud, no ****, about 30 steps and each progressive step requires that each previous one was done right and in order or you will find yourself just wandering in circles or with a precision raw power transfer assembly that fails in short order because of improper assembly.

    I post this same warning in every JS related topic.
    'Jackshafting is not for the faint of heart or mechanically challenged'.
    It can however be done well with the SBP parts supplied and gears change everything ;-}
     
  7. Fabian

    Fabian Well-Known Member

    One of the best tools to have in your tool collection is a digital vernier caliper. With some basic maths you can measure up dimensions then add or subtract numbers to find out if things will fit or if they will not fit when installed.

    It saves on having to use the method of an ever larger hammer to make things fit together.
    A digital vernier caliper can be purchased for as little as $20.
     
  8. sactownie

    sactownie Member

    Has anyone ever used aluminum pie tins or cans cut out for shims? Im sure I could have got it to fit if I had some different sized shims.
     
  9. sactownie

    sactownie Member

    Also no one has replied about my chain thickness. Right now the sprocket is dead inline with the engine sprocket but the chain is so wide its really close to the jackshaft plate.Is it ok to put a washer/spacer there or will I have problems? How close is your chain? pictures? I just dont trust that being so close.
     
  10. Fabian

    Fabian Well-Known Member

    Use the 415 chain supplied with the SickBikeParts shift kit.

    My assembly required the use of 2 large washers and one thin washer to get perfect alignment with the 10 tooth sprocket, so i guess there must be 3 or 4mm between the chain and the jackshaft plate.


    2013-023.jpg


    sickbi10.jpg


    sickbi13.jpg


    sickbi16.jpg
     
    Last edited: Aug 4, 2013
    bluegoatwoods likes this.
  11. KCvale

    KCvale Motorized Bicycle Vendor

    The JS kit comes with all 410 sprockets and new chain.
    I looked on SBP's web site for a 415 gear to match your 415 system but they don't have one.
    gasbike has a replacement 410 motor sprocket for $5.
    http://www.gasbike.net/bike-motor-part-small-chain-sprocket.html

    415 chain will run on a 410 sprocket but it will wander and wear odd and frankly 415 is a pain in the butt to work with, I'll take HD 410 any day for anything like this. Just swap the sprocket and be done with it as the kit comes with enough new 410 to do both JS sides.

    The kit has a block spacer and a variety of drop in shims to get your left chain tight.

    [​IMG]

    File the flat spot on the motor where the case seam is to get it all flat and level.

    Check that your bearings fit easily into the JS housing, file if needed and always needed if you paint it like my example.
    Also verify your shaft slides easily into the bearings, if not try filing the edge off the shaft ends.

    Put the main block on the bolts and get them started.

    [​IMG]

    Put your left sprocket on the shaft leaving a little nub as shown.
    To make things easy 'butter' your 2 keyways, in short this means rub them against a file so all sharp edges are softened so the keyway looks like a stick of warm butter.

    Then tighten the set screw that is not over the keyway, take it in and out a couple of times then remove the sprocket.
    File a flat spot on the shaft where the set screw mark is so the screw will sit on the flat spot when tightened.

    Remove both sprocket set screws, put the sprocket on with a black and 2 brass washers, then locktight the set screws in as this sprocket will no have to removed from the shaft again.

    [​IMG]

    Now just drop in shims until you get your chain tight and of course make sure all the bolts are tight. You should never need a 1/2 link here!

    If everything turns fine take the shaft with sprocket back out and mount your engine to the seat post.
    Start as low as low as you can go with the pedal crank on and put the sprocket/shaft back in. Note I don't have a front mount on yet, the support shaft and 2 U bolts are holding the motor to the bike.

    [​IMG]

    To make it easier on the right side just leave the motor chain off for now.

    (continued below)
     
    Fabian likes this.
  12. KCvale

    KCvale Motorized Bicycle Vendor

    (continued)

    Once the engine is back in don't bother with the engine chain, it will be easier to work the other side with it off.

    [​IMG]

    Now you start playing with getting the right JS sprocket lined up with the chain to the outer BB sprocket.

    Once you have the distance right screw the set screw that is not on the keyway down a couple of times to mark the spot, pull the shaft and file it like the other side and reassemble with locktight.

    [​IMG]

    Be sure to get your spacer washers between the clutch case and JS frame and tighten that 3rd anchor point.

    If you have forward cranks like this Macargi you may find your chain wants to hit the bottom of the motor like this.

    [​IMG]

    With a little more motor height and sometimes you can just grind the that cover plate down to the recessed bolt and it fits under fine like this.

    [​IMG]

    Note all of this was done with no front mount concerns as it is pretty easy to build a good front with right parts.

    Front continued below
     
    Fabian likes this.
  13. KCvale

    KCvale Motorized Bicycle Vendor

    (continued)

    Once the motor was where it needed for everything to function I had a pretty big gap from front of motor the front bar si I just use an left over shift kit block and a couple of those lame 'drill the frame' front mount plates to attach the SBP front mount to get close.

    [​IMG]

    The kits spacers and muffler clamp and we are secure up front.

    [​IMG]

    [​IMG]

    That black cable is my replacement CDI wiring by the way.

    You will no doubt need to raise your motor for the right side chain in short order but even 2 miles pretty much gets everything broke in, the trick is getting everything to that last JS sprocket perfect, from there it is all easy.
     
    Fabian likes this.
  14. sactownie

    sactownie Member

    KCvale excellent tutorial, thanks for posting!
     
  15. Fabian

    Fabian Well-Known Member

    Well presented photos KC

    I have never tried converting the engine output shaft sprocket from 415 to 410, but i do know that 415 specification heavy duty chain doesn't stretch as fast as 415 light duty chain.

    Never have i had a reason to down spec from 415 to 410 chain.
     
  16. Fabian

    Fabian Well-Known Member

    @ KC
    I have noticed that you are not running the clutch cable with a roller wheel system?

    Why?
     
  17. Fabian

    Fabian Well-Known Member

    I find that statement to be partially true because the dimensional difference between engine manufacturers is not consistent and even dimensional differences between engines of the same manufacturer can be surprisingly inconsistent.

    Most of my engines required 1mm to be removed from the rear engine mount to achieve a perfectly flat mating surface but i had one engine where the mounting face tab was significantly taller and required 3mm to be removed, thereby allowing the jackshaft frame to be placed in somewhere near an acceptable (centre to centre) engine output shaft to jackshaft measurement.

    Every engine is different; some can have wildly different external dimensions which is why some people complain that they can't fit the left hand side chain without a half link, and others say they have too much slack in the chain; requiring spacer shims to bring the chain to reasonable limits of unloaded tension.

    Another point needs to be brought into the equation: the Chinese (10 tooth) output shaft sprocket is frequently machined acentric, which is why the chain can be tight as a drum at one point in the sprocket revolution and looser than the front door of a lady of the night at another point in the sprocket revolution.
    For this reason you need a left hand side chain tensioner because it significantly dampens chain vibration, not to mention that you don't have to worry about chain stretch and can let it run it's own course till it reaches 100% stretch.
     
  18. sactownie

    sactownie Member

    Well I'm still trying to use the stock 415 chain with it. I have the chain tight and 1 thin and 3 thick washers and the chain has 1mm if even that of clearance from the jackshaft plate.
    The sprockets don't quite line up with 3 thick washers (1 thin and 1 thick and it is perfect alignment) and I don't believe this is going to be enough clearance.
    I don't know if I am trying to get this too perfect or if I am just SOL with all this.
    I don't have any money left to buy a new engine sprocket let alone other stuff I should have got.
    I know I need to use the thinner 410 chain that came with the shift kit for the engine output.
    I saw other threads where they ground down there engine sprocket to fit a 410 chain. I have a dremel, I guess Ill go look up a tutorial for that.
     
  19. sactownie

    sactownie Member

    Tried to remove sprocket to grind and now the cheap chinese gear puller tool is stripped! I cant get the gear off so now I guess I need to find a "real" gear puller. Jeezzuss!
     
  20. Ghost0

    Ghost0 New Member

    Ladies and Gentlemen, please STOP! As the designer of the Shift Kit and one who has dealt with both Fabian and KC extensively some of what is being throw out here is opinion. There is no need to run a 410 chain on the left side. I have never run a 410 chain on the left side. I did fit one up once and noticed that some engine output sprockets will accept them and some won't. Please follow the instructions. Use the chain that came with your engine for the left side chain no matter what size it is. Our 17 tooth sprocket is designed to work adequately with both. Second if you are having issue with getting the correct chain tension let me help. Send me your engine, chains, sprockets etc and let me fit them. Once this is done I would encourage you to report back to this group exactly what I did to resolve your issue. I will even pay to ship it back if you get it here. Send me a PM or email me on our website if you are interested.
     
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