4 stroke jack shaft with 7 speed cassette

Discussion in '4-Stroke Engines' started by skychair, Oct 22, 2015.

  1. skychair

    skychair New Member

    I thought I posted this earlier but evidently I did some thing wrong?????
    Anyhow Its been a while since I have posted ..probably 2013 when I built my 2 stroke.
    409327582.jpg

    I now want to upgrade to a 79cc Predator with a jack shaft running a 7 speed cassette.
    I have found very little info on what if any transmission to use for this setup.

    I have a 35t sprocket that I'm thinking of running on the left side off a 10t clutch.
    Anyone have any comments concerning this approach or am I going in the wrong direction????

    Just getting started so I'm open to suggestions.
    Good to be working on my bike again.
    Thanks in advance for any assist, Ron
     

  2. skychair

    skychair New Member

    some progress

    Hi all.....
    I did receive a response concerning my use of the following gear set, but not from here.
    It appears I need to find an additional 3:1 somewhere in the drive line??
    I'm still going ahead with the 35t sprocket for now, here is what I'm using:
    @ 6000 rpm with 10t clutch to a 35t sprocket on the left jack shaft (SBP 4 stroke kit), and
    a 10t sprocket on the right jack shaft to a 48t at the crank mated to a 30t that runs to a 7 speed cassette.
    with 12,14,16,18,21,26,32 tooth sprockets would it produce the following?? (ball park)

    12t 9.57:1 @ 48.46 mph
    14t 11.4:1 @ 40.62 mph
    16t 13.6:1 @ 34.10 mph
    18t 16.8:1 @ 27.62 mph
    21t 20.8:1 @ 22.28 mph
    26t 24.8:1 @ 18.76 mph
    32t 29.2:1 @ 15.88 mph 1st gear
    I really don't know if this will work but it seems as though it should......that was my question.
    Is this approach reasonable enough to accelerate from a standing start in 1st gear with out choking down, and allow advancing thru the gears to a sustainable 25+ mph.
    Just asking for opinions, if I'm all wet that's OK, I just don't wish to spend $150-$300 on a gear reduction 'transmission' when I have a gear that may(might) do the trick

    I tore down the bike and have completed painting a have the initial re-assemby done.
    Have parts coming in ....
    Had to use steel wool on the handle bar and goose neck to clean them up.
    Put on the dual brake lever and front brake disk 160mm.
    I slipped on a new twist shifter and determined that the throttle and kill switch when installed will prevent it's use, so I'm getting the thumb shifter, hope it works better.
    Have new rims, strips, and tubes, rims are Sta Tru with disk brake hubs on both, and a new 7 speed cassette.
    Here are a couple of pictures.... DSC00009.jpg
    DSC00011.jpg
    DSC00012.jpg 59367[/ATTACH] DSC00014.jpg
     

    Attached Files:

  3. skychair

    skychair New Member

    79cc Predator kill switch

    xDSC00015.jpg xDSC10023.jpg

    Thanks for looking
     
  4. SunkyWorks

    SunkyWorks Member

    This diagram allows 2 working switches. (someone posted this for the 212cc motor).
    Yours would require both switches to be engaged to kill the motor.

    I would flip the muffler clamp 180 degrees, but this will take more room.
     

    Attached Files:

    Last edited: Nov 3, 2015
  5. The_Aleman

    The_Aleman Active Member

    First, your motormount should _not_ be set up like that! It won't be stable! You need to flip the whole u-bolt around! Make sure the rears are right, too!

    Second, you will definitely need some kind of other reduction. The way you're thinking will just overspeed the heck out of your whole drivetrain.
    Engine to pedal crank reduction is only 16.8:1 That's about 60 pedal per 1K engine. Engine idles at 2K RPM rollin, your pedal drivetrain is moving at 120RPM(!)
    This means that when you're rolling with the engine idling at 2000 in a gear, the pedal drivetrain will be moving about as fast as you can possibly pedal.

    Your ratio numbers seem off, too. This is what I get from (10T+35T+10T+48T) and your 30T crank to 7-speed set:

    1) 32T-----17.92:1====8.6 @ 2000, 15.5 @ 3600, 25.9 @ 6000
    2) 26T-----15.56:1
    3) 21T-----11.76:1
    4) 18T-----10.08:1====15.3 @ 2000, 27.6 @ 3600, 46.0 @ 6000
    5) 16T-----8.96:1
    6) 14T-----7.84:1
    7) 12T-----6.72:1====23.4 @ 2000, 41.4 @ 3600, 69.1 @ 6000

    Basically a flimsy illegal underpowered motorcycle that won't really be pedal-able with the engine running. It might work until your derailleur grenades or it all eats a gear.
    I dunno how you think you can get engine PTO to SBP input with only 2 gears, either. It's gonna stick out a lot.

    I recommend a PMR jackshft, run your 35T #35 on that with the 10T clutch.

    10-> 35 -> 9T output to 17T SBP input, 9T SBP output to 48T outer crank = 35.26:1 engine to pedal crank reduction. This is 28.3 pedal cadence per 1K engine. Still kinda high.
    Add the 30T inner crank to your 7-speed set:

    1) 32T-----37.61:1====4.1 @ 2000, 7.4 @ 3600, 12.3 @ 6000
    2) 26T-----30.56:1
    3) 21T-----24.68:1
    4) 18T-----21.16:1====7.3 @ 2000, 13.2 @ 3600, 22.0 @ 6000
    5) 16T-----18.81:1
    6) 14T-----16.45:1
    7) 12T-----14.10:1====11.0 @ 2000, 19.7 @ 3600, 33.0 @ 6000

    Change all 9T to 10T instead: (35 pedal cadence per 1K engine)
    1) 32T-----30.46:1====5.1 @ 2000, 9.1 @ 3600, 15.2 @ 6000
    7) 12T-----11.42:1====13.5 @ 2000, 24.4 @ 3600, 40.6 @ 6000

    11T output (to 48 outer crank)
    7) 12T-----10.38:1=====15.0 @ 2000, 26.8 @ 3600, 44.7 @ 6000

    Also keep in mind that derailleur chains run at angles in certain gears. With your motor, this means some gears may not be usable.

    Check your chain angle in each gear so that you know which gears are safe before gearing.
     
  6. KCvale

    KCvale Motorized Bicycle Vendor

    You need a 4 to 5:1 gear reduction between the engine output and the jackshaft input.
    Your clutch doesn't even fuelly engage until ~3500 rpm.

    Not many transfer case choices for a Pred, Q-matic has one, ~$300, and it's big.

    [​IMG]

    It's just wide and too long to use with a SBP JS kit directly.

    The thing is, you don't really need gears with a 79cc, especially not 7-speed carousel gears.
    Just running a 79 direct drive to to 44T will get you going in a hurry and top 40 mph.

    But, I suppose if you could fit a ~55T sprocket on the left side of the jackshaft you might be able to pull it off without a transfer case.

    Otherwise you are looking at either going direct drive and wasting the shift kit, or just changing engines to the smaller 4-stroker and transfer case the shift kit is deigned for.

    Other Notes:

    You don't need a dual pull brake lever, you have no clutch, it's better to make them independent.

    As brute mentioned, you have your front muffler clamp on backwards, the U in the u-bolt goes around the frame tube in front, the flat metal of the base attaches between the flat clamp piece and it's nuts.

    Best make sure the 2 back ones are right as well.
     
  7. skychair

    skychair New Member

    Responses are in bold
    The_ALEman wrote in part

    First, your motormount should _not_ be set up like that! It won't be stable! You need to flip the whole u-bolt around! Make sure the rears are right, too!
    I do understand how the front mount is supposed to install, but I anticipated the need for more room to make chain adjustments, ...any how.....I now see that I can flip it around, rears are good to go, Thanks.

    Your ratio numbers seem off, too. This is what I get from (10T+35T+10T+48T) and your 30T crank to 7-speed set:
    Oh these are not my calculations I use the TZI ratio calculator, I dont have enough sense to figger ratios thru a cassette.
    The initial intent is to replicate the output reduction found on the 2 stroke (5:1??)...right?


    Basically a flimsy illegal underpowered motorcycle that won't really be pedal-able with the engine running. It might work until your derailleur grenades or it all eats a gear.
    Sorry I just dont understand....why do I want to pedal with a running engine???
    I dunno how you think you can get engine PTO to SBP input with only 2 gears, either. It's gonna stick out a lot.
    Well thats why I'm here asking questions, like... whats going to stick out a lot?????

    I recommend a PMR jackshft, run your 35T #35 on that with the 10T clutch.
    I'm liking the idea of the PMR setup....Would this work:
    10t off the clutch to my 35t on the PMR should get me 3.5:1
    10t off the PMR to 17t on SBP jackshaft should get me 1.7:1 for a total of 5.95:1
    From here a 10t off the SBP jackshaft to:
    1) the 48t at the crank and 30t back to the cassette.
    Or
    2) a 44t at the rear wheel, my sprockets wont allow the passage of the 2 piece hub clamp, so a 44t rear sprocket will need to be mounted to the disk brake hub. Im guessing a 44t...base on the above info should I go higher or lower???
    I'd like to keep the shifting abilities, but perhaps I cant
    .

    Do you have a measurement on the PMR from front hole center to center of rear shaft? Anybody???

    This is a good suggestion, thanks a bunch ALEman, I appreciate it. Ron

    Also keep in mind that derailleur chains run at angles in certain gears. With your motor, this means some gears may not be usable.

    Check your chain angle in each gear so that you know which gears are safe before gearing.
    Yes...I am aware that all gears might not be usable, Thanks again... ALEman


    KCvale wrote in part

    You need a 4 to 5:1 gear reduction between the engine output and the jackshaft input.
    Your clutch doesn't even fuelly engage until ~3500 rpm.
    I think as suggested above that I could get 5.95:1 using the PMR and SBP set up


    Not many transfer case choices for a Pred, Q-matic has one, ~$300, and it's big.
    It's just wide and too long to use with a SBP JS kit directly.
    Without ever handling one, I came to the same conclusion, not being able to readily connect from the Q-matic to the SBP, and the cost .
    The thing is, you don't really need gears with a 79cc, especially not 7-speed carousel gears.
    Just running a 79 direct drive to to 44T will get you going in a hurry and top 40 mph.
    I dont understand......Can I just run off the clutch 10t to a rear 44t with an idler to keep things tight?

    But, I suppose if you could fit a ~55T sprocket on the left side of the jackshaft you might be able to pull it off without a transfer case. See above...I'm looking at a 35t and a 17t running off the PMR setup....

    Otherwise you are looking at either going direct drive and wasting the shift kit, or just changing engines to the smaller 4-stroker and transfer case the shift kit is deigned for. Can you explain 'direct drive'
    Again KCvale, Thanks for the suggestions, I appreciate it all. Ron

    Other Notes:

    You don't need a dual pull brake lever, you have no clutch, it's better to make them independent.

    As brute mentioned, you have your front muffler clamp on backwards, the U in the u-bolt goes around the frame tube in front, the flat metal of the base attaches between the flat clamp piece and it's nuts.

    Best make sure the 2 back ones are right as well. KC's Krusiers Builds and NEW Parts Store
     
  8. KCvale

    KCvale Motorized Bicycle Vendor

    Direct Drive in my world is a left side drive to the back wheel with an independent chain.
    A Shifter is a drive that shares with the pedal system on the right side chain.

    Sure, if you run like a 13" wheel with 10" tall sprocket, wizzers do this with a belt and huge pulley on the back wheel.

    [​IMG]

    And even that can only run a 24" wheel for direct from engine drive.


    I think what is messing you up is the difference between a 2-stoke engine output and a 4-stroke output.

    The 2-stroke engines have a ~3.26:1 (I don't recall the exact number) internal reduction right in the engine on the right hand side where the clutch is (those 2 gears), 4-strokes don't, that's why you need an external clutch and gear reduction.
     
  9. darwin

    darwin Well-Known Member

    You 2 Einsteins will co-operate and get along, nuff said!
     
  10. skychair

    skychair New Member

    I dont get it.................
     
  11. The_Aleman

    The_Aleman Active Member

    Why _wouldn't_ you? Chevrolegs make more torque than any of these small engines. Direct-mounted clutches aren't the smoothest at low speed with that engine class, either.

    20T -> 82T for a reduction of 4.1:1 :rolleyes7:

    Probably aint gonna happen. I don't suffer fools very well; it's a nasty character flaw, I know.

    I'm not getting it, either. :whistling:
     
  12. skychair

    skychair New Member

     
  13. skychair

    skychair New Member

    Well I ran the bike set up with (10->35 / 10->48 / 30-> 32......12 cassette)
    Take off was strong and top end good @35mph, but I separated the derailleur chain to many times.
    So I reconsidered the shifting approach and decide to revert back to the way my 2 stroke was set up with 44T rear sprocket. I'll set aside the gearing for now, and revisit it in the future, always nice have to have an upgrade in the wings.:)
    The 2 stroke was 20->82 .... 11->44 with FDR @16.40:1
    The 4 stroke is 10->35 .... 9->44 with FDR @ 17.11:1
    This puts me as close to the 2 stroke FDR as I can get with the 35t sprocket, I'm off .71

    I installed a 44T sprocket with the 6 bolt mount to the rear disk brake hub, an used the 9T that came with the SBP 4 stroke kit.

    I modified (and poorly I might add) the SBP motor mount to accept the HF engine, and all's well so far.
    After my first test run with the clutch 10t to 35t on the SBP jack shaft, and 9t off the jack shaft to 44t @ the rear wheel.
    Take off is strong, bike wants to go, you can feel it.
    nice 13-14 mph @ 2800->3000 rpm
    29-30.4 mph as read from cateye Velo 7 at wot 6250-6500 rpm
    This is good enough for me right now.

    I still dont comprehend the need for 'transmissions' to build a 4 stroke????
    The SBP jack shaft is simple, changeable, and relatively inexpensive, least thats the way I see it.
    I added 2 chain tensioners to the left side to hopefully reduce adjustment while testing.
    Yes I'm going to run a 10mm self taper in the rear tensioner.
    Finalized my exhaust system, I think.
    Pictures included, thanks for looking, comments good or bad appreciated.
    Ron
    OH...MERRY CHRISTMAS everybody:p
     

    Attached Files:

  14. KCvale

    KCvale Motorized Bicycle Vendor

    A 2-stoke engine has a built in gear reduction and clutch.
    A 4-stroke has neither, so it has to be external.
    I call them a 'transfer case', it has the clutch and a simple gear reduction but has no shifting gears.

    Sure, you can do that with a jackshaft to use your bikes gears to do a shifting gear range, it just has to be one hell of a reduction without an initial transfer case reduction to start from like a 2-stoke has to start with is all.
     
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