212 or 420??

[hebert.mike]

Picking up a good sized frame today and building something to play around on with my girls. I want to have good power, but in my looking around I see that it’s basically impossible to get a D-N-R gearbox for the 420, especially with my intention to put performance parts into it.

is the 212 good enough to get up around 45-50 mph with prob 600 lbs of kart and humans?

Here is the cart, it’s leaning against a wall with the underside facing the camera. Needs a rear swing arm, tho I’m planning on doing a solid engine mount so I can have independent suspension on the back. I plan on searching a pick and pull for CV axles to make it work.

 

[madprofessor]

My current build is 520 lbs. without a driver, has a 212 hotrodded up to 15+ hp., and last test run only reached 31 mph. before a circlip fell off and motor quit. Problem is that all that horsepower is way up there in the rpm range, and until enough speed allows for enough rpm, it'll never get to use it. Currently experimenting with gear ratios to try and wind up enough revs to reach that hp. tipping point.
Save yourself the grief, get the 420. You'll already have 13 hp. off the line.

 

[hebert.mike]

Just go without the reverse ability, then?

 

[madprofessor]

Wow, tough dilemma there. Can't always have your cake and smush it in somebody's face too. Check out "gokartsusa.com" for overpriced showroom karts. Just read which ones have reverse, how much motor, etc. Might give you a better view of the range we're dealing with.

 

[hebert.mike]

Do those kinds of karts generally not have a reverse ability?

 

[hebert.mike]

Alright, so here’s the frame. Been told it’s a Hanmerhead Twister 150cc

 

[madprofessor]

The karts listed under "buggys" on above website for the majority do have a CVT (auto. trans. as they call it) with F-N-R gears. They range from about 7 hp. up to 13+ hp., a surprise to me. Thought the higher hp. didn't have reverse.
Note: Most of those are setups with the GY6 engine/CVT combo unit, and require parts only made for the GY6. There's hotrod parts available for them. Personally I don't want any setup where the engine case and the CVT are irrevocably a single unit. Look at pic below of what that looks like.
150cc PARTS (gy6store.com)

 

[Kartorbust]

You'll have to do a lot of searching to find a suitable FNR gearbox. A Predator 420 will give you plenty of power out of the box, especially for that much weight.

For gearboxes, there really isn't much out there anymore, niche market and all. You could find a wrecked gas powered golf cart and rob that gear box, it'll be geared to like 13:1 or there abouts. Another spot would be a Polaris Trail Boss 250 or 350 2wd quad. These use a CVT from the engine to the gearbox. 1:1 high range, 3.5:1 low range, and about a 3.5:1 reverse gear. These have a chain output with a #520 sprocket, usually a 12 or 13 tooth. You'll need to adapt a CVT to run it, but doable.

 

[madprofessor]

Imagine rolling a single-wheel-drive tire up to a round log, like 4" diameter. As you slowly try to climb over it, it keeps rolling backwards. That's how we did reverse when I was a kid.
TrailMaster 300 XRS-E (EFI) Dune Buggy Go Kart, Liquid Cooled, Chain Drive (gokartsusa.com)
If you have $4500 this is how you get a CVT w/reverse with 17.4 hp.
If they can build a tranny to take that, you'll find a way too.

 

[Pinhead]

This thread is a little aged but I don't see a resolution.

I found a heavy-duty FNR gearbox that can take some serious horsepower. Costs an arm and a leg, though: https://rpmgearbox.com/store/