170bhp go kart

[blown_vr6]

I'd recommend looking at fujimoto or rotax snowmobile engine's for a really fast kart.
We used to use a 400cc fujimoto engine for thrust in my old F2 hovercraft.
Never had it on a dyno but both types of engine are piece of cake to convert to direct drive and we used to run them in race spec with a redline of about
17-19,000rpm!!!! they're fairly reliable too you get about 6 hours use out of the engine at that spec, but you can do a re-build in about an hour once you've done one or two

Plus in a kart your not going to be running 19,000rpm direct drive, unless your going for landspeed records
Your biggest problem is always going to be putting the power down, even if you work on 200kg for kart and driver (you'll probably come out less than that if your using a normal kart chassis) 150bhp would give you 750bhp per ton

Just into perspective an RS6 is just over 200bhp per ton a Ferrari enzo is approx 400bhp per ton and F1 cars only make about 1000bhp per ton and look at the traction control systems they have to employ.

I'm not trying to put you off I'd be first in line for a go
just remember to weld on those wheelie bars and get the stickiest rubber you can.
Best of luck with the project though mate

Most of the karts that ive seen with bike engines are 6 speed.
Im sure you could alter the final drive to bring gearing into line with a bike.
Also the weight thing - i dont beleive a kart will be that much lighter than the equivalent bike that your robbing the lump out of, after all the share pretty much all the same bits and pieces and i dont believe the frame on a kart is that much lighter if at all than an equivalent bike.....
Im not saying it wont be slightly lighter but lets not forget pretty much 35% of a bike's weight is its rider.
As for the traction aspect - with the engine/box and driver right over the rear wheels id say it would have equal if not better traction than the equivalent bike especially when you consider the contact patch would be double on the rear axle.
Yes its going to have about 800 odd bhp per tonne with rider but there are cars out there that are not far off this sort of power.
Good luck with it - stick the Busa lump in

Pete.

[bazookachicken]

I see some of your point Pete,
the gearing etc could be modified fairly easily, but if you take the gixxerkart at the top of the thread they recon this weighs in at 135kg.
The wet weight of a gsx-r 1100 is 227kg so the bike is nearly 100kg heavier to start with.
I'm 15 stone or about 95kg so I'm no lightweight but if I was in the gixxerkart I'd have approx the same power to weight as the bike with no rider which makes a big difference the bikes going to be nearly 50% heavier by the time you've got a rider on it!
Thats why the weight transfer makes such a difference to the traction on a bike factor in things like the sag on the rear suspension when you open the throttle as well.
The kart granted has the weight of the engine over the back of it plus the driver but that weight over the axle stays pretty constant cause you've got no suspension.
Plus your centre of gravity is much lower in the kart so it doesn't constantly try and flip over on itself to the extent of the bike when you open the throttle, that natural turning force all adds to the bikes advantages in getting the power down in a usable manner.
Rich

[T2Andy]

You cant ride a bike with the throttle on the stop from the word go ,you have to be
progressive, on a cart you might do and just get wheel spin ,a super bike would spin and flip then crash.