Go Kart Drive train advice Predator 301/212

[Tomslick]

Hello,
I'm new to the site. I have searched around and found some of the information I'm looking for but nothing exactly like the setup i just bought. I purchased a Donkang Kart from a lady to build for my grandson and I to ride together. He is 8 and has autism, hoping he will drive it one day but will have to see. I have 5 acres in North Carolina. Lots of rolling hills and pasture. We are not going for high performance more on the dependability side.

I'm posting pics of everything I see folks asking about hoping that will save questions being asked of me. The Kart has a new 301 Predator on it, the lady I bought it from had just put a standard clutch on it which burned out in five minutes. Nothing shocking there. She also gave me a torque converter, its a TAV 30 with a 1" shaft diameter. She told me she installed the Centifrugal clutch because the kart went through a pack of belts in a hour. I believe this type kart had a GY6 style engine setup orignally but I'm hoping not to have to put that style back on it. I also have a good running Predator 212 I acquired during the beginning of this go-kart build. Kart has 22" atv tires right now. 31 tooth rear sprocket.

I am hoping someone could help me with ideas about the best way to set up this Kart. I am fine to install the smaller engine, or get a different torque converter if needed.
thanks

 

[Denny]

Awe, come on I thought this was going to be hard. Easy Peasy!
Step 1. Replace the 31 tooth axle sprocket with a 60 tooth sprocket.
Step 2. Install that 30 series set up and make sure it has a 10 tooth sprocket on it.
Step 3. And this is the most important one. Spend the $40.00 dollars or so and buy a GENUINE COMET belt for it! That 1 Comet belt will outlast about 10 cheap belts.
So to recap. 60 tooth axle sprocket, install the 30 series TAV II CVT with a 10 tooth drive sprocket for a 6:1 gear ratio and a GENUINE COMET belt.
it should work real sweet then. Oh yea, make sure you use sprockets for a #40 series chain. Any smaller may break.
One more thing you will still be able to use the same size tires. Save the smaller engine for another project.

 

[madprofessor]

60 tooth axle sprocket, install the 30 series TAV II CVT with a 10 tooth drive sprocket for a 6:1 gear ratio and a GENUINE COMET belt.

Copied Denny's complete sentence because I completely agree with every word of it. I'll go as far as to call it a minimum, especially with your tall tires. It will make a winning combination on even your tall tires, but if you skip any one of those steps, premature failure will enter your life.
I should add that the #40 chains/sprockets that Denny mentioned are 1/2" chains, where I see folks are most often using #35 chains/sprockets which are only 3/8" on the 30 series CVT's. Using #35 myself, but wishing I'd gone with 1/2" instead.
I'm attaching a link to a chart that shows info on a 3/8" and on (3) different 1/2" chains. Of the (3) chains in 1/2", you'll see that Denny recommended the beefier roller width #40 chain, I'm assuming that makes it a little stronger. Personally, I only care about mismatching a #40 sprocket to a #41 or #420 chain. Folks here have told me that's silly and no concern, it's done all the time with no problems at all, but I've got the OCD, really bad. Reading the chart and seeing the #41 and #420 chains have 1/16" narrower roller width worries me about a #40 sprocket being a little bit of a tight fit between the inner sideplates of the #41 and #420 chains
Again, I repeat, the other folks here say there's no problem with mixing 1/2" numbers. I'm just OCD.
Chain for Go Kart, Mini Bike | GoKarts USA®

 

[Tomslick]

OK, I noticed after looking for Comet belts it appears there is more than one size even for the 30 series. Is there a common size for these torque converters or will i need to figure out a measurement?

 

[Denny]

Oh there is way more than one size. If you’ll wait until tomorrow I’ll dig up the size you need.

 

[madprofessor]

I'm attaching the link for you that I do for everyone about CVT's (TC's), their belts, and how to measure for them, install and tension them, diagnose them, and maintain them. There's charts for various sizes of CVT's, you'll see the one that says "40 and 44 Series" in red, and "Symmetric 7/8" Wide" in dark blue under that. There you pick your driven pulley size, 7.5" or 8.5", and measure your C-C distance.
The important part for you while you wait on an answer from Denny is in the reading of all the text at the beginning of the (quite long) page, and then scroll down to the bottom of the page to read all the text there, about twice as much as on top.
You'll learn a lot about CVT's, and will never regret taking that time.
Comet Torque Converter Belts | Go Kart Drive Belts (gokartsupply.com)

 

[Tomslick]

Much appreciated! Found all the pulley and sprocket I need over at Monster. Belt chart was a gold mine of wisodm. Getting belt sized and ordering some comet spry lube as well. Now to find either master cylinder or complete brake setup and get this thing rolling.

 

[Willie1]

Probably too late to the party to help with your decision, given you ordered parts, but . . .

I'm guessing that the cart will be +/- 400 lbs and will typically be ridden leisurely in an off-road situation on hilly ground.
In my OPINION - I see a couple issues here.

First - personally, I don't install a 10 tooth drive sprocket on anything that I can avoid doing so, due to what I consider
not enough tooth/chain contact. For a 6.0:1 ratio I go to 12/72 tooth sprockets. And I'm a big fan of using a jackshaft
as a means of getting enough gear ratio while maintaining ground clearance. Yes, I know people run 10T sprockets with
reasonable success. I shoot for bullet-proof. If I am locked into a 10T I try to run an idler to improve tooth contact.
That said - I can't see, given the weight, terrain, tire size, etc. that a 6.0:1 ratio is enough gear reduction. While a
10/72 sprocket set would yield a BETTER ratio at 7.2:1, you are still dealing with a lot of weight and drag along
with a tall tire - not even considering the 10T sprocket debate. Personally, I would want more, not as much
for the performance issue as it is for belt life.
At that point a jackshaft would have to be installed. Using 12/20T for the first chain and 12/60T for the second yields
a 8.3:1 ratio, which should work well with a properly set up 30 series CVT unit. And yes, I realize that installing a jackshaft
may be more than some peoples budget, tools or experience may allow.

Again, just my opinion and why. Not going to get involved in 10 posts defending my views.

Enjoy your project.

 

[Tomslick]

Well I haven't pulled the trigger yet because im diagnosing the brakes and the same company keeps a master cylinder for this cart. Ill research your advice. I ve seen pictures of jackshaft setups but have no experience with them. I like the idea of bulletproof or as close to that as I can get. Thanks for the response.

 

[Tomslick]

Probably too late to the party to help with your decision, given you ordered parts, but . . .

I'm guessing that the cart will be +/- 400 lbs and will typically be ridden leisurely in an off-road situation on hilly ground.
In my OPINION - I see a couple issues here.

First - personally, I don't install a 10 tooth drive sprocket on anything that I can avoid doing so, due to what I consider
not enough tooth/chain contact. For a 6.0:1 ratio I go to 12/72 tooth sprockets. And I'm a big fan of using a jackshaft
as a means of getting enough gear ratio while maintaining ground clearance. Yes, I know people run 10T sprockets with
reasonable success. I shoot for bullet-proof. If I am locked into a 10T I try to run an idler to improve tooth contact.
That said - I can't see, given the weight, terrain, tire size, etc. that a 6.0:1 ratio is enough gear reduction. While a
10/72 sprocket set would yield a BETTER ratio at 7.2:1, you are still dealing with a lot of weight and drag along
with a tall tire - not even considering the 10T sprocket debate. Personally, I would want more, not as much
for the performance issue as it is for belt life.
At that point a jackshaft would have to be installed. Using 12/20T for the first chain and 12/60T for the second yields
a 8.3:1 ratio, which should work well with a properly set up 30 series CVT unit. And yes, I realize that installing a jackshaft
may be more than some peoples budget, tools or experience may allow.

Again, just my opinion and why. Not going to get involved in 10 posts defending my views.

Enjoy your project.

I noticed while researching the jackshaft question 20 toothed 40 series chained sprockets weren't plentiful. You didnt mention size but im guessing you would say stick with 40 series?

 

[madprofessor]

#40, #41, #420 chains are all 1/2", but the #40 is 1/16' wider between the inner plates (roller width), and that's always bugged me that a #40 sprocket might fit a little tight into a #41 or #420 chain, so I avoid #40 outright. Everybody else seems to have no problems with them though, so just chalk it up to my old-man-OCD. Or senility.
Both of the chains/sprockets suppliers below have sold me a lot of things, and both have always been stellar, in price, quality, and service. I noted some 20-tooths for you in 3/4" and 1" shaft sizes..................
#41 sprockets | eBay
41B20H-3/4" Type B Finish Bore Sprocket for #41 Roller Chain 20 Tooth | eBay
41B20H-1" Type B Finish Bore Sprocket for #41 Roller Chain 20 Tooth | eBay

 

[Willie1]

I noticed while researching the jackshaft question 20 toothed 40 series chained sprockets weren't plentiful. You didnt mention size but im guessing you would say stick with 40 series?

Realistically if you are only running a 212-225cc stockish engine a PREMUIM #35 series chain/sprocket drive would be fine, especially if it is being driven by a 30 series CVT. It would probably be the most cost effective setup and the smaller diameter axle sprocket would give better ground clearance than a 40/41/420 series chain. To be honest, a lot of times I used 40 series parts because we had them on the shelf in our maintenance shop at work - not because a 6-7-8hp, 3600rpm engine needed them.
While you can usually shop around on OMB, GPS and other kart websites (or Amazon, Ebay) and find everything you need for all the different chain, sprocket and jackshaft parts, I have had to occasionally hit an industrial supply house like McMaster-Carr for some of the quirky items.
Whatever series chain drive you chose, just like using only COMET CVT belts - don't cheap out on the chain. Cheap, stretched out chains eat sprockets.

 

[Tomslick]

After looking at how the cage is around this engine and the lack of space that provides I decided the jackshaft option would have to wait until i have time to figure out a way to mount it. I got comet belt and gears ordered for now to run torque converter. I appreciate all the wisdom and information shared.