CVT Help

[JCurtis]

Hi,

I'm relatively new to the world of go karts, but I'm looking to build one of my own. My goal is something I can take off road and get up to some nice speeds. For the transmission, I would prefer not to have to shift or have to manually engage a clutch. That led me to CVTs, and as I'm gathering parts for my build I found that there are not many inexpensive ones that can handle high HP. Here are about the only two I found:
First choice
Probably a bad idea
My engine will be a Predator 212 (governor removed) will some additional pieces of kit to increase performance. I am anticipating about 12 HP at around 6-7k RPM. Will the "First choice" CVT work or will I need a different one? If so, what do you suggest?

Thanks!

 

[Denny]

Your links ain’t working. A CVT is an excellent choice for what you want.

 

[JCurtis]

Your links ain’t working. A CVT is an excellent choice for what you want.

Whoops! Here you go!
First Choice
Probably a bad idea

 

[bob58o]

I used a cheap 30 series kit on a minibike using a mildly built 212 with black mamba jr camshaft and gx390 carb. It turned around 7500 RPM at 50 mph and did wheelies when I cracked the throttle. I think it had about 18” tires. I don’t remember the gear ratio I used. But probably about 7.5 : 1 sprocket ratio

 

[JCurtis]

I used a cheap 30 series kit on a minibike using a mildly built 212 with black mamba jr camshaft and gx390 carb. It turned around 7500 RPM at 50 mph and did wheelies when I cracked the throttle.

Thanks for the tip! I'd like to really rip around with this build. Do you think the CVT I have found wouldn't be the right choice for this go kart? I might need to use a sprocket to lower the gear ratio further.

 

[bob58o]

Thanks for the tip! I'd like to really rip around with this build. Do you think the CVT I have found wouldn't be the right choice for this go kart? I might need to use a sprocket to lower the gear ratio further.

Well I think the cheap TAV kit will handle 12 HP and 7000K rpm. You’ll need to use a gear ratio that helps with the off road hills, top speed will be an afterthought.

Something like 16” tires for an off-road buggy with a 212cc, 30 series TAV kit, genuine comet belt, 8T front sprocket, 60T rear sprocket.

6000 Engine RPM would be about 42 mph.

If using larger than 16” tires, I would probably want to use a 7” driven unit.

 

[bob58o]

This was my buggy with cheap 30 series TAV, 16” tires, 7.5 :1 sprocket ratio. Skip to like 40 seconds.

 

[bob58o]

the minibike I guess I had 13.5” tires and 6.75:1 sprocket ratio. 8T on front, 54T in back.

Skip to 2:15 for top speed run slightly uphill.


Black Mamba Jr Cam,
26 lb valve springs,
SS valves,
Billet Retainers and keepers,
ARC +0.020" Billet Connecting Rod,
gx390 carb,
NR zero degree adapter,
0.026 (or 0.028" ?) idle Jet,
0.042" Main Jet,
11.1:1 CR,
Head milled 0.037",
0.027" Head Gasket,
Ported and Polished,
30 series TC,
54T:8T,
13.5" Tires,
32 degrees BTDC ignition timing,
air filter adapter and performance air filter,
wienee pipe exhaust

 

[JCurtis]

Thank you so much for the replies, they're all very helpful! I'd like to get into modding the engine eventually so that I can get more HP out of it, at what point do you think the TAV will not be good anymore?

 

[bob58o]

Thank you so much for the replies, they're all very helpful! I'd like to get into modding the engine eventually so that I can get more HP out of it, at what point do you think the TAV will not be good anymore?

I dunno. I used a cheap 30 series with 7” driven on my highest HP, highest RPM engine. It turned about 8500 RPM and probably made more than 15 HP. I did swap out the weights and springs in the driver unit.


El Lobo Kit
from MiniChoppersSoCal.com
Banner Blue Powder Coat
6” Wheels
13” Tires
54T Rear Sprocket
Hydraulic Rear Disc Brake
Custom 18” Seat
1/2 Gal Spun Aluminum Gas Tank
Fold up Pegs with Custom Extension Mount
Tethered / Push Button Kill Switch
Tachometer
Oil Catch Can
8” Kickstand

30 Series Torque Converter
30C Driver Unit
Aluminum Die Cast Weight Pack Comet 202931A
White Garter Springs Comet 011190
(Upgrading to Yellow Springs Comet 216111)
7” Driven Pulley (Comet 31D7)
Comet 293591A Belt
10T #41/#420 5/8" Bore C Type Sprocket

212cc Hemi Predator
24mm FlatSlide Carb
Mesh Screen Air Filter / K&N Dry Flow PreCharger
NR Racing Hemi Head
Milled 0.040”
Ported
Spring Pockets Cut
28.5mm/25mm SS Valves with 3 Angle Valve Job
Automotive Style Keepers/Retainers
37lb Valve Springs
CrMo Pushrods 5.44”
NR285-0211 Camshaft
0.285” Lift
250 Duration
102 ICL
111 LSA
ARC +0.020” Con Rod
Ambush Racing 34 degree Hemi
Flattop Piston with Valve Pocket
Flywheel (set at 32 BTDC now)
0.027” Head Gasket
Autolite AR3910x Spark Plug
Head and Side-cover Stud Kits
ARC Top Plate

 

[bob58o]

Thank you so much for the replies, they're all very helpful! I'd like to get into modding the engine eventually so that I can get more HP out of it, at what point do you think the TAV will not be good anymore?

The better answer is when you realize 212cc is small for an off-road buggy and want to upgrade to a 420 and need a 1” 40 series TAV. That’s when hobbies started with $99 harbor freight engines turn into $1000 projects. lol

 

[JCurtis]

The better answer is when you realize 212cc is small for an off-road buggy and want to upgrade to a 420 and need a 1” 40 series TAV. That’s when hobbies started with $99 harbor freight engines turn into $1000 projects. lol

Haha, I can't wait, but my wallet sure can!

 

[panchothedog]

Hello JCurtis. Welcome to the forum. The torque converter that you list as " first choice " will work absolutely fine for any 212cc engine you will ever build. Even though many are advertised as 3 to 8 horse power ( or something that that ) they can handle MUCH MORE. The engine listed by bob58o in post # 10 is down rite hot. I think he is being very conservative when he guesstamates it at 15 horsepower. There is also additional power and speed to be had in tweaking or modifying the driver ( changing springs and weights ). Most any 30 series torque converter with the mounting plate will serve your purpose. I currently have 4 vehicles using them (all with modified ungoverned engines.) Other than wearing out a belt every once in a while, they are very dependable, and can take one
h##l of a beating.

 

[Denny]

The only thing is I would throw away the belt that came with the kit and get a GENUINE COMET BELT!!!!

 

[JCurtis]

Where might I find an authentic belt? I'm not sure the one on Go Power Sports will fit this transmission, but I could be wrong. Side note, where can I find wheels and tires? Everywhere seems unreasonably priced :/

 

[panchothedog]

Go Power Sports sells probably every size of torque converter belt made. They also have a chart that shows the different sizes, and how to measure it. Their own generic brand is decent ( better than the ones you find on Amazon ), they also sell Comet brand belts ( the best ). They also sell wheels and tires, along with practically every part needed to build a kart. It is far cheaper to buy and refurbish a used kart than to build one from scratch. Piece by piece ( new ) is a very expensive way to do it. If you can't afford wheels and tires, wait till its time to buy seat, axle, bearings, sprocket, steering wheel, steering shaft, spindles, brakes, and the list goes on and on. You'll have $1500 to $2000 tied up before you know it. Do yourself a favor and find a tired neglected kart of the style that appeals to you. With some elbow grease and fresh paint, you can have a new looking kart for half of what it will cost you to build a new one. Craigslist, Facebook Market place, and Offer Up are good places to find them. I have 4 and 3 of them were purchased as beaters. The other I bought new in a crate.