tav gear ratios

[manco12]

Hi,
It's been a while but I started riding the mini bike again ...

I was wondering the biggest tav sprocket I could reasonably put on my Puma would be. With 19" rear tire, 50 tooth rear sprocket, and 8 tooth tav sprocket @ 3600rpm that puts me at a 6.25:1 gear ratio... about 32 mph. Would an 11 tooth tav sprocket be even worth trying or would I not be able to get going, that would put me around 45 mph. And this is just for straight rides on pavement. All other times I'd switch the sprocket out.

I'm just wondering if I should get an 11 tooth or 10 tooth. I had a 9 tooth and it worked okay...
Thanks

 

[Stangrcr1]

The TAV low ratio on takeoff should be able to pull an 11 tooth sprocket, unless the secondary is already trying to go into overdrive early.

Check and see what hole the spring is in on the secondary. Put it in #3 if you go to the 11 tooth sprocket. That should keep in out of overdrive until you are moving.

 

[manco12]

The TAV low ratio on takeoff should be able to pull an 11 tooth sprocket, unless the secondary is already trying to go into overdrive early.

Check and see what hole the spring is in on the secondary. Put it in #3 if you go to the 11 tooth sprocket. That should keep in out of overdrive until you are moving.

Thanks, I'll order an 11 tooth sprocket and see what happens then. Will do with putting the spring in hole 3, you think I should also try a yellow spring while I'm at it or should the green be fine?

Thanks!

 

[Stangrcr1]

For the first test after getting the 11 installed, run the TAV without the cover, if you can. Watch the TAV and see how long it takes under acceleration before it "shifts". If it is still shifting early, then get the yellow spring.

 

[manco12]

For the first test after getting the 11 installed, run the TAV without the cover, if you can. Watch the TAV and see how long it takes under acceleration before it "shifts". If it is still shifting early, then get the yellow spring.

Will do, Thank You :smile:

And while I'm here I have an off topic question. Do you think I'd be able to run a TAV Driven with the sprocket on the outside? Like how you can flip a clutch around I guess... I would use one with a backplate and get a longer shaft. (which would likely add to much stress with a longer shaft unsupported?) Or would that be a bad idea? This is for a different low cost project go-kart. I'd like the engine as centered as possible because of my crappy absolute cheap as possible fun project type design :laugh:

Thanks!

 

[jeep2003]

yea i think that would put too much stress on the backing plate unless you put another bearing for support out there

 

[manco12]

yea i think that would put too much stress on the backing plate unless you put another bearing for support out there

The backing plate I got used is reinforced with some wels but I agree I still don't think it'd be smart.

Anyways, back to the mini bike for a minute. I tried the new sprocket with an old belt. It seemed to accelerate okay enough at first. The top speed wasn't any better though, I think it may have been largely because the old belt. When I can I'll try with the new belt.

But, will this gearing cause the belt to wear excessively?

Thanks

 

[Dartman ABQ]

The backing plate I got used is reinforced with some wels but I agree I still don't think it'd be smart.

Anyways, back to the mini bike for a minute. I tried the new sprocket with an old belt. It seemed to accelerate okay enough at first. The top speed wasn't any better though, I think it may have been largely because the old belt. When I can I'll try with the new belt.

But, will this gearing cause the belt to wear excessively?

Thanks

Ump this. How did the sprocket swap go?

 

[SCooke123]

was 7 years ago...........................................

 

[Dartman ABQ]

Yeah can’t find anything current.

 

[SAS289]

Yeah can’t find anything current.

11/50 gearing with a TAV and a 19inch tire is not a good idea. Once the belt shifts you would be running a 4/1 ratio. Not good.

 

[Dartman ABQ]

So what about a 11/60
Or a 8/60

 

[SAS289]

So what about a 11/60
Or a 8/60

11/60 would work ok but it would be better to save your money and get a 9 tooth to go with the 50 tooth and get near the same ratio as the 11/60. I used a 9/50 while waiting for my 60 tooth and it wasn't enough for me. I like the 9/60 gearing.

8/60 is great if you are doing slow speed trail riding with a TAV as long as you are careful with the throttle. With this gearing the bike will want to wheelie too easy if you hammer the throttle from a stop or at a very slow speed. I have to be careful with my 9/60. With this gearing (and 19 inch tire) you should not lose a lot of top speed if your engine is set up to turn at least 5200 RPM or so under load. I have an 8 tooth. It shouldn't happen but if my 9 tooth broke or goes bad I would run the 8 tooth with the 60. I will say the 8 tooth worked pretty good with a 50 tooth.

 

[MJL]

11/50 gearing with a TAV and a 19inch tire is not a good idea. Once the belt shifts you would be running a 4/1 ratio. Not good.

*Wonder how it would do with a Juggernaut? I can say with certainty that the Jugernaut shifts slower and has a lower final drive than the (stock) comet style driver. But, quantifying exactly how much is difficult. Maybe with a pair of calipers and a tachometer? And then there are lightweight flyweights, Tighter garter springs, stiffer secondary springs(and mounting holes), shift limit bushings to play with the Comet as well. I ran out of the desire to spend more money on the Comet driver before I exhausted all the combinations, but I think I could make 11/50 work if I had to.

*Just for conversation purposes. I know the thread is old, and even if it wasn't the OP might not be interested in "advanced" TAV tuning, I just find it interesting.

 

[SAS289]

*Wonder how it would do with a Juggernaut? I can say with certainty that the Jugernaut shifts slower and has a lower final drive than the (stock) comet style driver. But, quantifying exactly how much is difficult. Maybe with a pair of calipers and a tachometer? And then there are lightweight flyweights, Tighter garter springs, stiffer secondary springs(and mounting holes), shift limit bushings to play with the Comet as well. I ran out of the desire to spend more money on the Comet driver before I exhausted all the combinations, but I think I could make 11/50 work if I had to.

*Just for conversation purposes. I know the thread is old, and even if it wasn't the OP might not be interested in "advanced" TAV tuning, I just find it interesting.

I also find it interesting. Gearing is just as important to those of us that have near stock engines as it is to those with monster 8000 RPM engines.

The juggernaut I don't understand. If I wanted to run a big power high RPM engine on a Coleman I would put the best quality bearings in the jackshaft and run it. Then just tweek the gearing from there if needed.

 

[MJL]

I also find it interesting. Gearing is just as important to those of us that have near stock engines as it is to those with monster 8000 RPM engines.

The juggernaut I don't understand. If I wanted to run a big power high RPM engine on a Coleman I would put the best quality bearings in the jackshaft and run it. Then just tweek the gearing from there if needed.

The Juggernaut fixed all of my Comet driver problems instantly. No tuning, no messing around. I have 25+ hours on mine with zero issues. I could barely ride an hour before the Comet (genuine) would start to stick and needed cleaning and lube. The Juggernaut is quiet, with only a light clicking sound when it downshifts to idle vs the clang clang sound of the comet. The juggernaut also stays cool to the touch, vs the Comet which would blister you after a short ride. Undoubtedly better for the belt.

I haven't tried a higher quality cluch such as a Hilliard, but I find the engagement (even cleaned/abraded well) of the stock style clutches to be rough. You also get a lot of noise/vibration from the small jackshaft chain whipping around at 5000+RPMs. The belt in a TAV is much smoother. I'd take a TAV set up as a clutch, but not shift (by using a shift limiting bushing) over the stock Coleman/Baja setup any day.

With proper gearing and belt alignment, we have yet to shred a TAV belt (common complaint) despite over a hundred hours of use.

 

[SAS289]

Interesting... The stock drive pulley does run very hot.

I'm happy with 9/60 gearing and a yellow spring in the driven. More than likely this is as far as I will go. I don't really need more than that.

 

[Dartman ABQ]

So my Coleman CT200U has Mikuni 22mm carb. Stage one exhaust. It now has the go power sports Coleman 30seried. 60th rear sprocket. Not sure what the go pier sports came with for the small sprocket. If you not paying attention it will dump you. It’s a log puller. It does feel week at the top end. When to the trails today. Lots of low end needs did great. I think it’s perfect for trail riding. Stopped on a huge steep sandy hill in New Mexico. It pulled up the hill like nothing. Now it needs front forks they are on the way!