Is this engine powerful enough?

[andrew k]

Hi i'm building my 1st kart/buggy. I need a few suggestions on what size engine will give me wheel spinning acceleration(on dirt) and about 50+mph top speed. I have a 125cc 4stroke pit bike engine that has 10hp and a 4 speed gearbox. The bikes top speed is around 55mph. I originally planned using it in the buggy but now that I've welded the majority of the framework i don't think its up to the job. The frame is made mainly from 25x25x2.5mm square tube and its pretty heavy. All the rest of the steel i'm using has 2.5mm thick walls aswell. I'd say it'll weigh about 120+kg without me in it when its done. The alternative is to sell my pit bike and get a 250/400cc road bike engine off a breakers. The second option is probably 150euro on top of the money i'll get from selling the bike. Is the 125cc 4 speed enough??
(i'll try upload some photos...)

 

[blackparis]

sounds like a weak 125 to me.. Mine has 33hp stock.. and I got a reed kit, and nice aftermarket pipe..

I picked up a wrecked bike (kawasaki kx125) for 500$ and alraedy sold 200$ of salvaged parts.. pretty much all i have left is the motor/trans

 

[Kenny_McCormic]

A 400+ cc bike engine will do what you want.

 

[andrew k]

sounds like a weak 125 to me.. Mine has 33hp stock.. and I got a reed kit, and nice aftermarket pipe..

I picked up a wrecked bike (kawasaki kx125) for 500$ and alraedy sold 200$ of salvaged parts.. pretty much all i have left is the motor/trans

big difference between 125 2 stroke and 4 stroke.....

 

[motor_head]

i vote for a goldwing motor (1500cc) hehehe

 

[anderkart]

Ahaaa... why screw around here, how about a V-12 Allison.

 

[anderkart]

You havent said how much you weigh yet, but if you like lots of power I think you'll be disappointed with that 125 in a heavy rig. If you can swing the extra cash, I think a realistic goal would be something in the 250 to 500cc range. I'd probably prefer one of those 4-stroke motocross engines for size/weight reasons but most any street bike engine would be cool too.

 

[Rickracer]

120 kg would be about 264 lbs. WOW, that's a pretty heavy kart. Torque and gearing will be more important with that than top end HP, but I'd agree that you'll probably not be all that happy with the power. If you can live without "wheel spinning" take-off, and could settle for about a 50 mph top end, the 125 would work though.

 

[modelengineer]

I don't think it's enough power...

 

[andrew k]

This is the most recent picture I have. I have the steering setup, rear swingarm, and front wheels attached since I took this pic.....

 

[DK shredaaa]

nice it looks a little cramped but i dont know, i highly doubt the motor you described will have tire spining capabilities id go for a yz 250

 

[r_chez_08]

i thought i saw that kart somewhere. is it this with some modifications? if so, it looks like 13hp clones are used on some. apparently it reccomends a 5hp engine, but i think over 10 would be best. that 125 engine should probably be ok as you already have it. hereis a vid of someone with an 18hp motor on, and it looks pretty bad a$$
http://www.youtube.com/watch?v=G4PhbX6hoWk
also, with that steering/ suspension setup, how does the angle of the wheels stay correct to the ackerman theory?

 

[andrew k]

Thanks for the quick replies. I'm wondering am i better off getting an 250cc 4 stroke dirtbike engine rather than an engine from a roadbike. I understand there are a lot of electronics involved in a roadbike (sensors, altenator, starter motor etc.), rather than a dirtbike engine which would be much simpler in design. Are roadbike engines alot more hassle to use..???

 

[andrew k]

i thought i saw that kart somewhere. is it this with some modifications? if so, it looks like 13hp clones are used on some. apparently it reccomends a 5hp engine, but i think over 10 would be best. that 125 engine should probably be ok as you already have it. hereis a vid of someone with an 18hp motor on, and it looks pretty bad a$$
http://www.youtube.com/watch?v=G4PhbX6hoWk
also, with that steering/ suspension setup, how does the angle of the wheels stay correct to the ackerman theory?

ya thats the one....I'd say i'd get tired of a 5 hp engine fairly quickly and I kinda want something with a manual clutch and gearbox.....and about the Akermann geometry, I moved the pitman arm closer to the back of the kart so it is not on line with the spindles. when i turn left the tie rod pulls the spindle on the left wheel on a tighter turning circle than the tie rod pushing the right spindle. its hard to describe without a diagram.....

 

[blackparis]

i thought i saw that kart somewhere. is it this with some modifications? if so, it looks like 13hp clones are used on some. apparently it reccomends a 5hp engine, but i think over 10 would be best. that 125 engine should probably be ok as you already have it. hereis a vid of someone with an 18hp motor on, and it looks pretty bad a$$
http://www.youtube.com/watch?v=G4PhbX6hoWk
also, with that steering/ suspension setup, how does the angle of the wheels stay correct to the ackerman theory?

Looks like the weight balance is too far forward.

IDK.. I'd prefer to understeer al little more... Plus I Like to launch my cart long and high distances.. I dont want to nose dive...

 

[r_chez_08]

??? confused. i meant with the suspension surely the wheels go from this (\ /) like they are supposed to be (over exaggerated) to this (l l)

yeah i thought a 5hp engine was pretty low, as it looks like they are only just getting enough fun with 18hp in the vid lol

 

[modelengineer]

Roadbikes aren't really difficult to use. The wiring is MUCH simpler than in a car (well... on my GS-500 it is) and in a road bike you usually get electric start which is a real plus when you have to get out of the 5-point harness and seat to kick start it.

But I agree that a 250 dirt bike engine would be better than a 125cc bike engine/5hp/10hp/18hp industrial engine.