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Thread: New guy needing some gearing help

  1. #1
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    Jun 2018
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    New guy needing some gearing help

    Hello all I have been searching the forums for some answers but am coming up short.
    I am putting together a 250 UAS kart and need some advice on ratios and where to get the parts I need.
    I have a 2014 Ultramax chassis and just bought a Taft cased kx250 that was advertised on here and Facebook from another member.
    I have a basic understanding of the jack shaft gearing and how to figure out the ratios
    I知 a little confused by what was on the jack shaft for gearing when I purchased it and what I need to get me in the ballpark for rpms on the track I intend to run
    It has a 30/60 pulley on the crank side, a 18 sprocket on the jack shaft and was told around 62 on the axle. If my math is right that would put the final drive ratio at 6.89
    That seems very steep to me.
    The primary track I intend to run now is stateline speedway
    3/16 MILE DIRT TRACK WITH SLIGHTLY BANKED CORNERS
    300 FT. STRAIGHT A WAY 40 FT. WIDE from their website.
    The people I知 talking to are saying 4.80 -5.50 is where I want to be.
    The clutch will be set to ingage at 6200-6500 it is a burkey wet clutch
    I have a Taft pipe I assume good to somewhere around 10,500ish?
    I知 thinking I need to be around 24 tooth on the jack shaft sprocket to get the full range of gearing I may need at different tracks with the rear sprockets available.
    I also have a jack shaft tuff hub and am not sure where or if I can get a 24t sprocket for it.

    I need to know if this will put me in the ball park in your opinion.
    Any recommendations would be very much appreciated.
    And any sources for that tuff hub sprocket it is 35t

    I intend to go to stateline speedway maybe eriez and AMS occasionally

    Thanks Tim

  2. #2
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    Oct 2013
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    iowa
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    Math appears correct.
    Realizing 6500 stall equals 13,000 rpm
    At the engine.
    This thread had some info. Some one here will be able to help better then I.
    https://karting.4cycle.com/showthrea...ckshaft-ratios

  3. #3
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    Oct 2013
    Location
    Frisco, TX / Sardinia, OH
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    Quote Originally Posted by Nocero View Post
    Hello all I have been searching the forums for some answers but am coming up short.
    I am putting together a 250 UAS kart and need some advice on ratios and where to get the parts I need.
    I have a 2014 Ultramax chassis and just bought a Taft cased kx250 that was advertised on here and Facebook from another member.
    I have a basic understanding of the jack shaft gearing and how to figure out the ratios
    I知 a little confused by what was on the jack shaft for gearing when I purchased it and what I need to get me in the ballpark for rpms on the track I intend to run
    It has a 30/60 pulley on the crank side, a 18 sprocket on the jack shaft and was told around 62 on the axle. If my math is right that would put the final drive ratio at 6.89
    That seems very steep to me.
    The primary track I intend to run now is stateline speedway
    3/16 MILE DIRT TRACK WITH SLIGHTLY BANKED CORNERS
    300 FT. STRAIGHT A WAY 40 FT. WIDE from their website.
    The people I知 talking to are saying 4.80 -5.50 is where I want to be.
    The clutch will be set to ingage at 6200-6500 it is a burkey wet clutch
    I have a Taft pipe I assume good to somewhere around 10,500ish?
    I知 thinking I need to be around 24 tooth on the jack shaft sprocket to get the full range of gearing I may need at different tracks with the rear sprockets available.
    I also have a jack shaft tuff hub and am not sure where or if I can get a 24t sprocket for it.

    I need to know if this will put me in the ball park in your opinion.
    Any recommendations would be very much appreciated.
    And any sources for that tuff hub sprocket it is 35t

    I intend to go to stateline speedway maybe eriez and AMS occasionally

    Thanks Tim
    Where is your clutch located ? On the primary ratio or secondary ratio side ?

  4. #4
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    Jun 2018
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    25
    Quote Originally Posted by Chris Cooper View Post
    Where is your clutch located ? On the primary ratio or secondary ratio side ?


    On the primary side

  5. #5
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    Jun 2018
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    Quote Originally Posted by flattop1 View Post
    Math appears correct.
    Realizing 6500 stall equals 13,000 rpm
    At the engine.
    This thread had some info. Some one here will be able to help better then I.
    https://karting.4cycle.com/showthrea...ckshaft-ratios
    Thanks for the reply I actually have read that thread. I知 very new to this and it really just raises more questions for me. As far as the 6200 rpm engagement that is what im being told from the previous owner. I assume that would be engine rpm? Not jackshaft?

  6. #6
    Join Date
    Oct 2013
    Location
    Frisco, TX / Sardinia, OH
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    I would start with the following:

    - find the needed clutch engagement speed and max usable range for the pipe (if the clutch engagement for the pipe needs to be 10,500, your clutch needs to come in at 5250 engine rpm if you keep the 30/60 ratio).
    - change the driver on the jack-shaft to get your spread for the track.

    I ran into similar issues with our set-up. I bought a few different jack-shaft drivers and then changed the gearing on the axle to get close. We only have to make very small incremental clutch adjustments.

  7. #7
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    Jun 2018
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    I知 very unfamiliar with the power band of two strokes is 5250 engine rpm I assume?
    I知 finding the terminology when talking to people most confusing. Does this seem normal? How do I figure the needed clutch engagement?
    I know this combo ran good I致e talked to people who saw the kart run and said it was real fast so I壇 like to leave the 30/60 if it痴 usable? I just don稚 see how a 18t jack shaft sprocket worked from what I知 hearing that I need for a final drive.

  8. #8
    Join Date
    Oct 2013
    Posts
    555
    He has a Birky clutch guys which is not like a Bully 4 stroke based clutch. Your 30t-60t equals a 2:1 so you take your secondary side which you say is a 18t-62t which is a 3.44:1, multiply that by your primary 2:1 equals a 6.88:1. Yes this sounds a little high for the track you are describing. If your engine is engaging at 6200RPM your clutch is engaging at 3100RPM. As far as clutch engagement and top RPM, it all depends how your engine is built. From my experience I think your clutch engagement is a little high but again it is how your engine is built. Were you shown how to check the oil in the clutch? Do you know how to adjust your clutch measuring your spring height?

  9. #9
    Join Date
    May 2015
    Location
    north central nebraska
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    1,300
    I just Google searched kx250 powerband.

    Should give you some idea of where it kicks in.
    Clutch engagement should be somewhere around peak torque.

    Two stroke power comes on quickly. Falls off on the top end quickly.

    Just some thoughts to get you going.

  10. #10
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    Jun 2018
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    25
    I do have a hand writen setup sheet from birkey and was shown and read online how to check/ fill the clutch. Just not sure where to set it? When I figure it out am I setting it at 1/2 the engine rpm. Peak torque number where I壇 set the engagement ?
    And could use some final drive recommendations.
    I値l include what I know about the engine from the PO. In another post

  11. #11
    Join Date
    Jun 2018
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    25
    Taft converted 2001 kx250. it's a 258cc. 3 races on piston, rings, jug. It's a steel sleeve. Bottom end has maybe 10 nights on it. Electric water pump. the ignition is seletra. Motorworx has redone the mount and jackshaft as well as all the engine work. It has been ported and polished. Will come with everything to race except the pipe (we have a broken Taft pipe) (now fixed) and the battery. Birky clutch Banshee radiator and all the plumbing. It's also got an upgraded Mikuni slide carb pump around on gas with Hilton CF reeds.

  12. #12
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    Location
    north central nebraska
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    On clutch engagement, if the clutch hits and the engine bogs, engagement speed too low.
    If the clutch hits and the engine revs right thru, engagement too high.

    There's some space between for personal preference.
    A couple standing starts will give some idea of what you're looking for.

    For most circle track, once clutch locks, should not unlock at race speeds.
    Sprint racing, low speed corners, there may be an advantage to the clutch slipping.

  13. #13
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    iowa
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    Quote Originally Posted by Nocero View Post
    Thanks for the reply I actually have read that thread. I知 very new to this and it really just raises more questions for me. As far as the 6200 rpm engagement that is what im being told from the previous owner. I assume that would be engine rpm? Not jackshaft?
    Your right . The Birkey on the primary side vs a clutch on secondary side is quite different .
    I was wrong .
    Airtight Garage Est 1982
    Waller Racing
    Phantom Chassis
    Dover Power
    Paid 4 cycle subscriber

  14. #14
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    Jun 2018
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    Can anyone direct me to where I could get a jackshaft sprockets to fit a tuff hub? I致e been googling and can稚 seem to find them.

  15. #15
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    north central nebraska
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    http://www.out2win.com/catalog/bully_clutch.html#tuffy

    Not my favorite, but a start.

    Or better still, the source.

    https://www.buller.net/Category/bully_misc

    I'm sure advertisers on this site can help you out as well.

  16. #16
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    Thanks!

  17. #17
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    Why would you want drive sprockets for a clutch. I go to Martin Industries and buy 3/4'' shaft sprockets, they arehigh quality and very affordable.

    Can Motorworx tell you where peak torque is? It would make setting the clutch much easier.

  18. #18
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    Quote Originally Posted by Brian Montgomery View Post
    Why would you want drive sprockets for a clutch. I go to Martin Industries and buy 3/4'' shaft sprockets, they arehigh quality and very affordable.

    Can Motorworx tell you where peak torque is? It would make setting the clutch much easier.
    Because I知 a newbie and I知 not sure what I知 needing.
    I got a 3/4 tuff hub for the jackshaft with the box of parts. I figured it would be quick and easy if I need to change the sprocket.
    I already ordered the sprockets I need so too late now.

    I plan on calling Motorworx to see if I can get any info.

  19. #19
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    Greenville, SC
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    2,261
    Quote Originally Posted by Nocero View Post
    Because I知 a newbie and I知 not sure what I知 needing.
    I got a 3/4 tuff hub for the jackshaft with the box of parts. I figured it would be quick and easy if I need to change the sprocket.
    I already ordered the sprockets I need so too late now.

    I plan on calling Motorworx to see if I can get any info.
    It is very easy to find them at Motion Industries. I like to buy from karting businesses but if I don't have to place an order I buy sprockets and belts at my local Motion Industries.

  20. #20
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    I meant to say Motion Ind. I get Martin sprockets there. Thanks Rainman

    Do the Tuffy gears have the keyway broached in them?

  21. #21
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    Quote Originally Posted by Brian Montgomery View Post
    I meant to say Motion Ind. I get Martin sprockets there. Thanks Rainman

    Do the Tuffy gears have the keyway broached in them?
    There is no key way the sprocket bolts to the hub which stays on the jackshaft.

    If someone could tell me how to upload pictures from an I phone I値l post pics of what I have for a hub

  22. #22
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    That's right I saw one a couple years ago. The nice thing is you are less likely to have to re-align after a gear change.

  23. #23
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    Let痴 see if I can get a picture to work

  24. #24
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    Well that didn稚 work one more try
    Attached Images Attached Images

  25. #25
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    There we go
    This is the hub

  26. #26
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    Seymour, Indiana
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    Those are made by Buller. You can buy them direct from Buller or other kart shops that sell them.

    22t thru 28t (could be more)

    Brian #89

  27. #27
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    Yep got a couple coming

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