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  1. #1
    Senior Member TheDullCarbide's Avatar
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    TAV2 Driven-6" or 7"?

    I have a TAV2 on my Ty-Rail gokart. It came with a 6" driven. I assume it was chosen because it had a wider shifting ratio than the 7". I had a 7" with belts lying around from my old Yerf Dog. Tried it out, and , the TORQUE. It wasn't just the fact that it was an inch bigger, but the belt just hooked from a dead stop. The old 6" would slip around until 10mph when it decided to give a . This 7", because of the extra surface area, can handle the low end torque.

    In the past, I've tried to gear the 6" way low (like 24mph top end), and I could never get the engine to rev past it's usual 3800rpm at top end. This 7" though, I had it geared to top out at 40mph and it revved! I got 4700rpm holding the governor open (little scary running stock ).

    I guess if you want low-end torque or if you're racing and revving in high gear, the 7" is a no-brainer. The 6" looks good on paper, but in real life it slips. It probably works for lower HP engines, but not my 6.5.

    Disclaimer: This is just my experience. I'm not trying to be right, just sharing.

    Ty

  2. #2
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    What belt did you go with? It looks like the CL distance falls between belt sizes. Did you slot the backing plate?

  3. #3
    Senior Member TheDullCarbide's Avatar
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    Quote Originally Posted by OUTLAWD View Post
    What belt did you go with? It looks like the CL distance falls between belt sizes. Did you slot the backing plate?
    I'm using the -90 belt right now. It's a little tight, but it's still pretty new so maybe it'll stretch. It doesn't seem to take off at idle but I wonder how long the bronze bushing will last. I'm putting off ordering the -91 until I'm done with my other projects. I don't have the original cover for it but I made a sheet metal one that just covers the top. I shimmed it up so I didn't have to slot it.

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  5. #4
    Senior Member super nate's Avatar
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    the six inch pulley has a 9% overdrive in high and most engines cant pull past it. the seven inch pulley has a one to one ratio in high and will let the engine rev. the correct belt for the seven inch tav is 203591. always buy a good belt frombeltpalace.com they are the best belts out there

  6. #5
    delray's Avatar
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    also using a bando(beltpalace.com) belt for a 30 series. not a real big fan of the comet units. they do have there weak spots. but this belt is holding up ....
    this setup is using the 7inch driven and i don't get any slippage even with the flat side belt design.

    beltpalace.com doesn't give this belt away$$ but well worth the money.
    the only other input i would have to say is makesure you have the correct distance from center of crank to the center of the driven. for example if your measurements are between 6 13/16 - 6 7/8 it needs to be there.
    down side on this belt. they dont make it for a 20 series....yet


    https://www.oldminibikes.com/forum/p...er-bolt-5.html

  7. #6
    delray's Avatar
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    TheDullCarbide
    I'm using the -90 belt right now. It's a little tight, but it's still pretty new so maybe it'll stretch. It doesn't seem to take off at idle but I wonder how long the bronze bushing will last. I'm putting off ordering the -91 until I'm done with my other projects. I don't have the original cover for it but I made a sheet metal one that just covers the top. I shimmed it up so I didn't have to slot it.
    i don't think this type of belt is design to stretch very easy. built to hold its tolerances a lot better then a china or even a true comet belt.
    did you every fix your problem. kind of sounds like your center to center distance was off just little.

  8. #7
    Senior Member super nate's Avatar
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    the bando belt from beltpalace is the best you can buy and yes they are not cheap but you do get what you pay for. ive been using them forever and have had no problems they don't slip or stretch. my 390 has a 40 series torque converter with modified driver that launches at 5000 on nitrous and the belt is still hanging in there. cant say as much for the pulley shaft I did bent it but hay its a 20 shot of nitrous on top of a 40horse engine lol

 

 

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