Torque converter Question

[zbillz]

Been reading here for the last week or so.

Just picked up an old offset kart with a Briggs 5hp motor. It has 11 tall inch slicks, 15 tooth clutch and a 71 tooth sprocket.
It takes a little bit to get going but my son had it clocked from his phone at around 21mph. Seems like there is a little more left but do not have enough room in front of the house to try.

Been looking at the Comet torque converters to get more acceleration but it looks like the driven sprocket that comes with the Comet is a 10 tooth. According to the speed calculators this would really kill the top speed.

Can the driven sprocket on the Comet torque converter be replaced with a 15 tooth or do I just get a smaller diameter rear sprocket?
Thanks

 

[c-gar]

high there. if you just want the answer, yes, you can get a 15 tooth gear for the TC. i did.
https://www.ombwarehouse.com/torque-converter-sprocket-35-15t-5-8-bore.html
note that mine wasn't a perfect fit and had to be filed a little to fit over the shaft key.

I've been working with my gear selection also so here is my experience if it can help you in any way.

http://www.diygokarts.com/vb/showthread.php?t=40242

http://www.diygokarts.com/vb/showthread.php?t=40291

summary of the experience so far is that the TC would spin up over 5000 rpm with the 12 tooth so i was worried about burning it up. after installing the 15 tooth it still feels snappy and will climb a hill. on a flat it will get up to about 4500 rpm. i haven't been out on a long ride with my gps to see exactly what speed it's capable of, but it feels fast enough for me. i'm hoping that having it limited by taller gearing makes for a happier TC than if it was over-revved but i'm not sure.

 

[zbillz]

Great work on your kart! Hoping mine will fit without much modification.
Did you buy a clone or the Comet?

 

[landuse]

Use a smaller sprocket. You will have a bit more acceleration that way. You won't take as long to get the kart moving as it does now. Top speed will be less though

 

[bob58o]

I’m guessing you are set up for #35 chain. The 10T sprocket included is for #41/#420 chain.
The 12T sprocket included with most of those kits is for #35 chain. You usually can get both included. But like previously mentioned, you can buy replacement sprockets.

 

[itsid]

yes, either #35 or 219 (which I think is a likely scenario)

Since #40 would be 11.7" in diameter with 71T and
thus would cause a minor issue with just 11" wheels

Now: just also change the axle sprocket

it doesn't matter if you change chain pitch with it.

it'd only upset the current chain ratio a tiny bit:
for a 10T #40 TC for example just go with a 47T axle sprocket
and you changed the ratio from 4.73:1 to 4.7:1
or with a 12T #35 TC sprocket just get a 57T axle sprocket
and you changed the sprocket ratio from 4.73:1 to 4.75:1

No big deal either way.

Even if you do not change the axle sprocket and it's indeed a #35 and no 219
you still end up with more than 21mph top speed

With the ratio your son's currently running at I doubt there is much left in terms of top speed tbh..
The engine just doesn't have the torque to accelerate much further I'd say.

'sid

PS if you have a 219 setup you will have a very hard time finding a 219 C-Type sprocket (that's what the TCs need)

 

[zbillz]

Thanks for the input guys! It is a #35 chain. Going to buy the TC from Go Power Sports. Will also use a 55t and the included 12t TC sprocket. Looks like it may be a tight fit? Hoping the Briggs 5hp will do OK with that gearing.

 

[landuse]

Thanks for the input guys! It is a #35 chain. Going to buy the TC from Go Power Sports. Will also use a 55t and the included 12t TC sprocket. Looks like it may be a tight fit? Hoping the Briggs 5hp will do OK with that gearing.

Just keep in mind that the gear ratio might be a bit high (4.5:1). It should hopefully work with 11" tyres though. Just don't ever get bigger tyres without re-gearing

 

[c-gar]

Did you buy a clone or the Comet?

I got the unbranded clone from OMB warehouse with the extra comet belt / bushing and mix of metric/standard hardware. I still had to get a longer bolt to go into the shaft on the engine because of the width of the TC clutch setup.
I had the original clone bushing break off quickly and needed the replacement. I also have changed the belt out to the comet after the first one showed me I had some pulley alignment adjustments to do.

 

[zbillz]

The torque converter worked out perfect. Had to raise the motor a bit and grind a little on the frame for the rear sprocket to clear. The seat had to get moved also.
The converter kit had all the correct hardware included.
Acceleration is night and day compared to the clutch. Well worth the effort.