Suggestions for bike engine for kart build - what engine?

[m1tch]

Hi all,

I am just about to start on a bike engined kart project, due to the high cost of kart engines - due to the specific regs for each of the classes - im going to be using a bike engine instead as they are compact and have a gearbox attached.

I am basically needing help on what is the best/most commonly supported/modded engine you can currently get that won't break the bank. I am going to be going with the engine in the original position next to the seat on the right, however in future I do plan to extend the frame and fit a larger engine!

The kart will be drag raced at Santapod for a bit of fun, I might also take it on some other tracks as well, but need to find a decent engine to use, the 250cc superkarts use full sized circuits

My criteria are:

Lowish cost
Ease of spares
Well supported with regards to guides/knowledge
250cc or above
Manual box (will have a shifter in the kart to change gears)
Carbed - easier is better
Single cylinder - needs to fit in OEM position at the moment
Prefer 2 stroke as they make more power per size

I have seen that a Yamaha yz250 seems pretty popular, but I know that quite a few dirt bike engines are now going 4 stroke with a reduction in power and increase in weight.

As some people on here maybe aware, people seem to like putting rather powerful bike engines into karts, examples include this 600cc 'Gixxerkart'

https://www.youtube.com/watch?v=_nQW0jsqv4Y

And a 1000cc nitrous drag kart:

https://www.youtube.com/watch?v=G7Q8t7XJ5hY

[P.]

Funny you shoudl post this, I have a CBR125 engine on ebay and if it doesnt sell we are going to shove that in a little kart

[m1tch]

[HD]

Its probably putting out no more than 15bhp mate

If you are gonna go 125, get one out of a crosser that is around double that!
____________________
Rusty '02 Vito Camper + CBR600F3

[m1tch]

[HD]

Guess you could try that but then you have to buy a new topend.

It appears that 125 may be enough https://www.youtube.com/watch?v=NG3MxRAHvy4&feature=related

Although that does sound like a highly strung 2 stroke crosser engine by the way it stays in the powerband haha!
____________________
Rusty '02 Vito Camper + CBR600F3

[m1tch]

[HD]

Fuck that for a laugh!

And would have thought most of the motocross engines would be putting out that. Suzuki Rm, Yamaha Yz, Honda Cr, Kawasaki Kx, Tm and Ktm Sx. Although Tm are a smaller company and some say KTM's are less reliable.
____________________
Rusty '02 Vito Camper + CBR600F3

[m1tch]

[Blackrandomap...]

Kx250 motorcross engine, Did it a few years ago! Very fast. . . Maybe a little too fast
____________________
1x 2001 Yamaha R6 1x 2000 Yamaha R6 !For Sale! £2500 1x 2003 Cbr600rr Racebike 1x 2004 Wr450 Sumo 1x 2001 Ktm520 Sumo

[m1tch]

[kestrel]

[m1tch]

[mr jamez]

In before Paulington reminds us all that he used to race go karts.
____________________
NSR 125F > BROS 400 > NC30 > BROS 400 > Trumpet S4 > '97 VFR 750

[m1tch]

[HD]

[m1tch]

Looking around at engines it seems that the Honda CR125 engine puts out around 40bhp? It looks like there are quite a few mods and tweeks people know of on the CR125 engine so it might be worth me saving up a bit for one of those?

Looks like basic upgrades like a better pipe, reeds and a bit of porting/cleaning/flowing and it seems to react well

https://twostrokemotocross.com/2009/05/budget-racer-2001-honda-cr125/

Ive just found a CR250 complete bike up for £400, needs a top end rebuild, but at least I know there will be complete bikes for sale for not a crazy amount of cash and I can then use the cooling system and sell on the frame etc and parts to recoup some cash.

[Kickstart]

Hi

Do you want to race this in a kart race series? If so you will probably quite severely limited on the engines you can use. If not then you can probably pick up an ex kart engine that is either no longer allowed or no longer competitive for reasonable money.

Any 2 stroke engine not normally used on a kart might make it harder to get an engine.

The 250cc 2 stroke will be around 50hp, way short of the 2 stroke twin super karts.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[m1tch]

[Kickstart]

Hi

The Rotax 257 engine is a 2 stroke single used in some of the cheaper 250cc race karts, and also used in some enduro bikes (none common in the country unfortunately). Kart version has a closer ratio gearbox and no power valve.

But a CR250 engine is probably cheaper and easier though. Or a CR500 engine to be really silly.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[m1tch]

[Pete.]

I fitted a KH100 engine into a fun kart years ago for my stepson when he was a lad. Originally it had a Briggs & Stratton engine that was just awful. I cut the frame out of the bike with the engine still in it and welded some angle iron across the bottom rails then mounted that onto the cart with Mini gearbox extension rubbers for flexible mounts. The front was just packed up with long bolts and stacks of washers to tension the chain.
Throttle pedal and cable came out of a skoda rapid at the breakers and a cortina bonnet stay was the gearchange remote. I cut the bike's rear brake pedal off including the mount and shortened it by cutting just at the crook and hammered a rubber bar grip onto it to make a gear lever welded to the frame alongside the driver's thigh, connecting the bonnet stay via a home-made clevis onto the hole for the brake light spring.
I cut off the silencer and welded a cap on the front end, then cut a hole in the side and welded some mini exhaust pipe to it that connected to the stock downpipe, the silencer was mounted across the rear of the frame.
Fuel tank was the 2-stroke oil reservoir mounted on the back of the seat stay/roll bar.

The KH was ideal as it had the airfilter in a pod on the negine casing so there was no airbox. It wasn't terrifically powerful but then the lad was only 11. It had 2 main problems:

Overheating - the engine was behind the seat and not much fin area on a roadbike engine anyway
The gearing was way too low - first was useless, second was lower than first. Didn't have any gears to swap so it was limited to 4 gears and topped out at about 40mph.

20 years ago now and I can still remember the fun I had making it and the laffs he had driving it. Cops would come and shoo off the crossers but the gokart was so quiet they left him alone.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[m1tch]

[Pete.]

People dragrace all manner of crazy things. I once saw a guy race an Aeriel 3 fitted with a CBR600 engine. It threw him off badly and broke his arm I think.

Just remember the crossers have a vicious power delivery, and that will tend to break things between the engine and the wheels.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[m1tch]