Engine and drive train

[rovert21]

I want to build a 2 seater off road go kart in the future. I'm still trying to decide whether to go with a 420cc predator engine or some sort of ATV/snowmobile setup with reverse. I would like to find an ATV/snowmobile setup, but I'm not finding any reasonably priced ones on my local craigslist. I was wondering what cc ATV/snowmobile engine would be of equal power to the 420cc engine?Also If i got the 420cc engine and did some power mods to it would a comet fnr box and comet 40 series still hold up to a kart of this style or should I really try to find an ATV/snowmobile motor? Or let me no if there are any other options I was looking around and there does not seem to be many heavy duty fnr boxes or cvts on the market for a reasonable price. So let me know what you think?

 

[OzFab]

Let's assume by "420cc engine" you're referring to a Honda or clone:

Apples & oranges. A 420cc Predator has a max hp rating of 14hp. Yes, you can modify to increase that but, for example, a 150cc chinese pitbike engine puts out around 11hp so, I would say a 200cc ATV engine would be around 15-18hp; a 250cc would be up in the 20s.

For what you'd spend on a 420 predator, a fnr gearbox & a CVT, you could probably buy a new chinese atv

 

[Doc Sprocket]

I'll second the above.

 

[jamyers]

Yup, look for a Chinese arc or scooter with a GY6 engine/cvt, and use its power train. And shocks, brakes, etc


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[poordad]

I hate to disagree but I have a 150cc Gy6 a 250cc CF250 and a 420cc HF Predator motor on three different buggy's and the clone is about a quarter more on power than the 250 and the 150 isn't even in the same range. on hills the 250 only has a chance against the 420 in a low gear.

I would say if your cart/buggy is 250 - 400 lbs a 150 could be ok, between 400 - 600 lbs a 250 would be fine provided it has a low gear and at 400 - 700 lbs a 420 would work fine.

the HP ratings on these motors has very little to do with real math and mostly marketing the 150 and 250 are labeled high to make people by them and the 420 is marked low to pass industrial safety rules.

a polaris box works well with the 420 and if you set up using the clutches, changing up to an atv / snowmobile motor later will be easier.

 

[smgs92]

^Listen to him he helped me out on another forum.

 

[jamyers]

^^ good points, the smaller-displacement engines make their hp through rpm, while the larger predator already has the displacement to make it at lower rpm - with more room to grow.

Still, a CVT like on a gy6 is a great thing, although a Comet 40-series on a big predator would be better (if more expensive)...


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[smgs92]

If he is planning to mod the 420 I'd go with a snomo clutch it's cheaper and will hold up as he adjusts power.
I don't see the benefit in suggesting a lower grade CVT for a higher price.

 

[spyder1968]

if i had it to do over.....i would prob go with a snowmobile clutch myself. and reverse would be a HUGE plus for an offroad kart !

 

[rovert21]

Thanks everybody, some very useful information. I think a polaris/ snowmobile clutch would be pretty similar, is one easier to adapt to a 420 predator? Is there a certain model polaris/ snowmobile I should look for or a specific part number?

 

[exenos]

The only sled clutch you can use on a regular industrial engine without a machined shaft is a 1" 94c duster from comet. The other sled clutches use a taper to hold the clutch on.

 

[smgs92]

The only sled clutch you can use on a regular industrial engine without a machined shaft is a 1" 94c duster from comet. The other sled clutches use a taper to hold the clutch on.

No you can buy an adapter for snomo clutch to 1in shaft.

Any of the clutches will work and you can mix and match yamaha, polaris, artic cat whatever. Just pick up some decent looking ones for cheap. I wouldn't pay more than $15 for the secondary. You don't need one with springs or weights because you'll have to change them out anyway.

 

[poordad]

something to look for depending on where you live is an older polaris ATV as this will get you a set of clutches set for about 450lbs and a transmission. Alot of times the motor is no good and people just want them out of the yard, keep an eye out