Home Forums Tech Talk Gear Ratio Dilema

This topic contains 10 replies, has 5 voices, and was last updated by  TJ Koyen 10 months, 3 weeks ago.

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  • #59551

    Tom Turner
    Participant

    Last Fall I took a road trip to Road America Kart track in Wisconsin. It was the first time I had been to that track, so not only did I not know the lay of the track or seat time for usable breaking points, which was not a big deal, because I was so happy to just be there and racing a very fun group of competitive people.  I Loved my time there alot!! I entered the 360# Yamaha Heavy Can class.  I  ran a set-up of #35 chain and 9 teeth on the clutch side and 70 teeth on the axle side.  Needless to say, I was way off the pase!  Both from track experiance and incorrect gear choice.  Can I ask what I should have ran as far as a Gear Ratio to at least be in the Ballpark?   Most in the field were running 219 chain and of coarse, were regulars there.  I would love to go back and at least be a bit more competitive.  Any advice you have for me will be very appreciated!

    Tom Turner

    #59568

    tony zambos
    Participant

    Tom,
    I sure some one will post up a gear ratio for your class. But having run the weekend at the track, you should be able to come up with a reasonable guess at the right ratio. Were you over revving the engine at the fastest part of the track or turning too few rpm’s in the corners? What was the clutch stall speed set to?
    What’s going to be more important is your chassis setup. Nothing is going to kill your lap times more than a poor handling. My advice is to take to gear ratio that someone will graciously provide, and maybe add two teeth on the axle. Then work on the chassis until you can run with everyone else and knock off the extra teeth.
    Good luck.

    LAD Specialties / tony kart / rotax / kt100

    #59571

    Tom Turner
    Participant

    Yes Tony, I was <span style=”color: #444444; font-family: Arial, Helvetica, serif; font-size: 12px; line-height: 21px;”>over revving the engine at the fastest part of the track.  The stall speed was about 11,000.  </span>I was only there for the evening race that day, so I only had a couple test sessions that evening, before the races started.  I should have asked some questions that nigt of other racers but I did not.  Hindsite is 20/20.

    Thanks for your Ideas.

    TOM

     

    I

    #59583

    TJ Koyen
    Participant

    Tom,

    Your stall speed is pretty high. Last year at 360, we ran around 8900 for stall speed on an L&T clutch. That’s about what we ran on our old Horstman clutches too.

    What was your max RPM?

    And why are you using #35 chain instead of #219?

    Team Driver - Innovative Performance/Tony Kart // Owner - Oktane Visual Custom Helmet Paint and Graphic Design

    #59584

    Tom Turner
    Participant

    Tony,

    That stall rpm is an estimate.  I’m not totaly sure what it really is.   And I believe I saw 12,000+ as a max RPM.  It made me a little nervous.  I thought it to be TOO HIGH!  As far as the #35 chain vs #219   … the #35 chain  is what I’ve always run in the past, I can switch over to 219 but I would need all new gears. What would be the advantage in switching to 219?

    Tom

     

    #59587

    Gary Lawson
    Participant

    Yamaha can should be around 14000 as a starting point. You need to know for sure what rpm you are going. It’s the first thing you should have changed after your first session on track of it was too high. Ask questions next time. Most would be happy to help.

    #59633

    TJ Koyen
    Participant

    To expand on Gary’s post, 14,000 RPM+ should be the maximum RPM you should be shooting for, not clutch stall. Clutch stall should be between 8500-9000 depending on your engine’s powerband. We’ve run 4-hole can Yamahas up to 15k for years with no issues.

    No one I know runs #35 chain in 2-stroke karting. So by switching to 219 you’ll be comparing gearing ratios in apples-to-apples terms. Here’s a good little write up on 219 vs 35: http://www.tsracing.com/Techtips/TSchain.html

    You really need a MyChron or RPM gauge of some kind to make any meaningful adjustments to gearing or clutch stall.

    I’ve been to the kart track many times there but can’t remember the gearing. Also they usually run several different configurations depending on what series is running that day. So I would email the guys at the club to ask them what they are running. Or post in their Facebook, there seems to be a pretty good following there: https://www.facebook.com/groups/347111190778/

    Team Driver - Innovative Performance/Tony Kart // Owner - Oktane Visual Custom Helmet Paint and Graphic Design

    #59650

    jt colegrove
    Participant

    Hey Tom,

    I have a used MyChron 4 with GPS05 unit I’m getting rid of.  It logs things like your engine RPM, temperature, GPS speed, lateral and longitudinal acceleration, and creates track maps.

    If you had one, it would be really easy for you to give us lots of information to troubleshoot your problems and get you going in the right direction.

    A MyChron 4 costs 350 new, and the GPS is 300.  I’ll sell them both shipped to your door for $340.

    #59674

    Tom Turner
    Participant

    TJ,

    I do have and used a tach. / temp.  gauge  a “Didgitron”  One thing is that there seems to be no simple way to varify a stall speed ?  is there?

    The information on 219 vs 35 was very helpful

    So Thanks for your input. I appreciate it!

    Tom

    #59681

    tony zambos
    Participant

    Tom,
    First off, listen to TJ and Gary.

    Second, this is a good time of year for you to look at maintaining your engine and clutch. If you have no idea how much run time is on the engine, get it looked at. Could prevent you from having a short weekend at the track. Since the stall speed was over the norm, check the clutch for being worn or warped.

    Last, consider upgrading to a MyChron 4(4 or 4-2t), a Data Key plus a GPS module. Time at the track gets hectic. With the MyChron and Race Studio on a pc you can go back over your data at a quieter time. AiM does have seminars on Race Studio and they’re cheap. Only issue is that the closest one to you is a little west of Milwaukee.

    LAD Specialties / tony kart / rotax / kt100

    #59697

    TJ Koyen
    Participant

    Tom,

    A Digitron will do. Checking stall speed is actually pretty simple. From a dead stop, mash the gas and watch the gauge. It should level off for a bit while the clutch stalls. That’s your stall speed.

    Here’s a video of me starting a race. About 2 seconds in, you can hear the engine level off and stay at a consistent RPM for a few seconds. That’s where the clutch is stalling.

    Team Driver - Innovative Performance/Tony Kart // Owner - Oktane Visual Custom Helmet Paint and Graphic Design

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