gearing question

[Cart Man]

My kart has 12 hp, tav2 torque converter, 10 tooth clutch sprocket,
72 tooth drive sprocket, 420 chain. Going to replace drive sprocket. What size would give me good torque with decent speed approx. 40 mph. Thinking of going to 54 tooth drive sprocket. Any input would be appreciated.

 

[chancer]

Try this:
http://www.diygokarts.com/speed-calculator.html

 

[tazmannusa]

What is your tire diameter ?

 

[Cart Man]

22 turfs in back.

 

[OzFab]

My kart has 12 hp, tav2 torque converter, 10 tooth clutch sprocket,
72 tooth drive sprocket, 420 chain. Going to replace drive sprocket. What size would give me good torque with decent speed approx. 40 mph. Thinking of going to 54 tooth drive sprocket. Any input would be appreciated.

22 turfs in back.

Hang on, something's not right there, a TAV2 on a 12hp engine? Is that even possible?

As for the gearing, the 22s make all the difference; if you fit a 54t sprocket, you may reach your desired 40mph but you'll probably destroy the belt in the process...

I say you may reach 40mph because, with the high gearing, the TAV may not fully engage so, you will never reach the potential top speed.

You'd be best to stick with the 72t which, without the TAVs 0.9:1 overdrive, will reach mid 30s

 

[Cart Man]

Here is picture of the converter. Someone said it looked like tav 2

 

[tazmannusa]

Yep thats a 30 series rating about 8 hp max . With 22" tires I would leave the gearing where it's at, you could try an 11 tooth but I think you would just burn the belt up

 

[OzFab]

Yep thats a 30 series rating about 8 hp max .

It sure does; I want to know how it fits on a 12hp engine shaft, they're usually 1"... or are you estimating the output of a smaller engine with mods?

 

[Cart Man]

Engine tecumseh model # OHSK120 22024F

 

[colestreasures]

It sure does; I want to know how it fits on a 12hp engine shaft, they're usually 1"... or are you estimating the output of a smaller engine with mods?

I think the shaft must step down from 1 inch to 3/4 inch.
Cole

 

[tazmannusa]

They do make that setup with a 1" bore driver, I have one myself

 

[itsid]

Yes, 1" driver isn't exactly hard to find..
but the series 30 is rated up to 15hp... most forget about that, because the TAV2 Kit is NOT
(that's indeed rated to only 8hp... the reason is yet unknown but likely because of the back plate)

That picture does NOT show the original TAV2 backplate.. soooo
15hp should be possible with an original comet series 30.

'sid

PS Assuming a weight of no more than 150kg (~330 lbs)
a 54T rear sprocket might actually just work with a 12hp engine,
It'll still shred the belt sooner than necessary, but the TC should be able to kick into overdrive on a flat straight road.
personally.. I'd say a 6:1 should be your best bet for picking the "fastest" yet still durable gear ratio.

 

[tazmannusa]

Yes, 1" driver isn't exactly hard to find..
but the series 30 is rated up to 15hp... most forget about that, because the TAV2 Kit is NOT
(that's indeed rated to only 8hp... the reason is yet unknown but likely because of the back plate)

That picture does NOT show the original TAV2 backplate.. soooo
15hp should be possible with an original comet series 30.

'sid

PS Assuming a weight of no more than 150kg (~330 lbs)
a 54T rear sprocket might actually just work with a 12hp engine,
It'll still shred the belt sooner than necessary, but the TC should be able to kick into overdrive on a flat straight road.
personally.. I'd say a 6:1 should be your best bet for picking the "fastest" yet still durable gear ratio.

Where are you getting 15 HP rating for the 30 series ?

 

[itsid]

Where are you getting 15 HP rating for the 30 series ?

I always get what I want

JK..
from Hoffco / Comet themselves

Model 30 Series (Asymmetrical)
The model 30 uses a 3/4" top width belt. The belt mass in No. 30 is desirable in applications requiring extra rugged driving ability, such as dune buggies, go-karts, mini bikes, ATV's
.....

Specifications
Diameter: Internal 4"; External 3.69" - 5.31"
Housing: Cast Iron
Bore: 3/4" 7/8", 1"
HP: up to 15
...

'sid

 

[tazmannusa]

I always get what I want

JK..
from Hoffco / Comet themselves



'sid

LOL

I think that might be a typo on the web page, The PDF manuals state 8 hp 2 or 4 cycle and I can say from experience I ran a 30 series on a GX390 for a little bit 7.5:1 ratio with 18" tires and it would slip the belt if you poured the coals to it at slow speed . It will work but I wouldn't expect it to last long

 

[itsid]

LOL

I think that might be a typo on the web page, The PDF manuals state 8 hp 2 or 4 cycle and I can say from experience I ran a 30 series on a GX390 for a little bit 7.5:1 ratio with 18" tires and it would slip the belt if you poured the coals to it at slow speed . It will work but I wouldn't expect it to last long

*shrugs*

I never paid attention to that part of any of the pdf manuals obviously...

you're right, the series30 manual states a max of 8HP just like the TaV2 manual *shrugs*

one must be a typo (maybe a "revisional difference")
*shrugs*

I can't tell wich one;
but since you'd rather be safe than sorry I tend to agree that it's safer to stay below 8hp.

If in doubt
(Or I had the personal NEED to actually run a series 30 on more than 8hp..)
I'd call hoffcocomet and ask wich one's the typo

Maybe one of you could do that, since you're much closer geographically than I am
just to be sure, once and for all ...

On the other hand.. a lot of "modified" predators run a Tav2 kit successfully, and what appears to me as in a durable manner.
Smaller wheels, yes.. but still easily crack the 10hp limit.
I'd even say one or two are easily in the 12hp region...

Again, I can't tell for sure;
but I assume, that you can either run a gentle gear ratio and a bit of additional power, or you're stretching the gear ratio a bit and apply no more than the rated max power,
but not both at the same time.
*shrugs*

One day we will know

'sid

 

[tazmannusa]

*shrugs*

I never paid attention to that part of any of the pdf manuals obviously...

you're right, the series30 manual states a max of 8HP just like the TaV2 manual *shrugs*

one must be a typo (maybe a "revisional difference")
*shrugs*

I can't tell wich one;
but since you'd rather be safe than sorry I tend to agree that it's safer to stay below 8hp.

If in doubt
(Or I had the personal NEED to actually run a series 30 on more than 8hp..)
I'd call hoffcocomet and ask wich one's the typo

Maybe one of you could do that, since you're much closer geographically than I am
just to be sure, once and for all ...

On the other hand.. a lot of "modified" predators run a Tav2 kit successfully, and what appears to me as in a durable manner.
Smaller wheels, yes.. but still easily crack the 10hp limit.
I'd even say one or two are easily in the 12hp region...

Again, I can't tell for sure;
but I assume, that you can either run a gentle gear ratio and a bit of additional power, or you're stretching the gear ratio a bit and apply no more than the rated max power,
but not both at the same time.
*shrugs*

One day we will know

'sid

For sure best bet would be to call them and hope whom ever is on the end of the line knows what there talking about !
I don't think I would be to concerned running a modified 212 with the 30 series unless you really went wild with it, a 212 with 10 or 12 hp still wont have the low end torque that the 390 will have

 

[itsid]

yeah well. no it will not have the low end torque of a gx390..
but the max torque will likely be somewhat comparable.

So I still go with "there's some margin" left for additional abuse,
it's just much more difficult to find the sweet spot without breaking belts every other day,
when you're getting closer to the "real limitation"

Ryan mounted a series 30 TAV2 kit (a clone) to a predator 420 IIRC...
and he claimed, that for the short times he's actually running it, it works fine.
(can't seem to find the thread ATM)

'sid