Building a 250 Superkart

[pts106]

As promised here are some pics of the kart I built to complete the final two race meetings of the local 250 Superkart Championship. (This is after crashing my PVP)

Bare Chassis (1)
Bare Chassis (2)

The chassis is known as a "Stealth". Made in South Africa, very similar to pre '06 PVP, but seamless cold rolled steel. Good for one, maybe two seasons max if you stay out of trouble. I had it powder-coated battleship grey.

Subframe, spindles, steering rack and brakes (1)
Subframe, spindles, steering rack and brakes (2)
Subframe, spindles, steering rack and brakes (3)

In these pics you can see the front subframe, spindles, stub-axles and brake system installed. To save a lot of work later, it's crucial to get the setup as close to exact as possible at this stage. The spindles need to be sloping 18 degrees to get the kingpin inclination and weight distribution right for cornering with a solid rear axle. Camber in front is set at zero or one degree positive.

Brake callipers are four pod Kellgates in front, 1 x sixpod on the rear axle. All three discs are full floating. I used zip ties and peel & stick foam strips to hold the braided lines in place. Bias is adjustable on the master cylinder mounted in the centre of the front subframe. Steering rack is also Kelgate.

Engine (1)
Engine (2)

I have two Rotax twins, a race engine and a spare. Opted to install the spare engine in this kart.

Undertray, fuel tank & radiator (1)
Undertray, fuel tank & radiator (2)

I kinda like the 'battleship' look. Undertray with integrated diffuser is fibre glass. Tank & radiator are aluminium. The diffuser creates a fair amount of turbulance at high speed. That's good for reducing drag and making things uncomfortable for the guy behind trying to catch your slipstream.

Steering wheel & dash

I was worried the small Sparco steering would be hard to steer, but it turned out okay, pun intended

Revcounter and heat guage are old school. I still prefer to see needles instead of a digital display. Got the revcounter from Padgetts in the UK, the heat guage is a probe type car one that I modded. This time I mounted a bike style clutch lever directly on the gear lever. It's easier (than a foot clutch) to keep the engine going in the event of a spin. Gear pattern is 1st away from you, 2nd to 6th towards you.

Complete, without bodywork (1)
Complete, without bodywork (2)
Complete, without bodywork (3)

Setup worked out fine. First time on the scales the corner weights turned out perfect - 48kg/49kg in front, 63kg/63kg rear, with me in the kart (not suited up). Once I had everything together something came over me and I decided to buff some bling into the radiator, heat transfer pipes and exhaust canisters.

Complete, with bodywork (1)
Complete, with bodywork (2)
Complete, with bodywork (3)
Complete, with bodywork (4)

The build took six weeks in total and I'm quite happy with the way it turned out, considering it was the first time I tried my hand at building and setting up a 250 kart. BTW - the sticker on the nose is a ripoff of the Porsche crest and it reads "Shopping Trolley" instead of Porsche / Stuttgart, cause that's what I call the little things - Modified Shopping Trolleys. He-he. Anyway, I was on pace the first time out at Kyalami, although the day didn't turn out so good. Race report from Kyalami

And believe it or not, I crashed this kart at the last race meet of the season. Thankfully it's fixable. Race report from Wesbank I'm fixing this kart and putting up for sale. I'm now building a brand new PVP for 2007.

Phew! Took a while to construct this post. Hopefully you find it entertaining.

Cheers,
Pierre.

[Gilles lives!]

Hi Pierre,

Can I congratulate you on your informative post, this will come in very handy for anyone looking into starting racing in superkarts.

What tyres do you run, are they controlled and how long do they last. I know when I was involved there was no limit on how many tyres you used in superkarts.

Paul.

[pts106]

Originally Posted by Gilles lives!

Hi Pierre,

What tyres do you run, are they controlled and how long do they last. I know when I was involved there was no limit on how many tyres you used in superkarts.

Paul.

We're on controlled Dunlops. You can practice on whatever rubber you want, but for quali and two 10-lap heats you're only allowed one new set, plus one front and one rear spare.

[Jonas]

Hi Pierre,

once again you have a very clean and tidy machine. I notice you´re running mechanical hand clutch. How hard is it to pull, really? I will run hand clutch for next year and also considering a hydraulic one.

I notice that you run a single radiator, no problem with overheating?

Best regards
Jonas

[pts106]

Hi Jonas.

Thanks for the compliment.

The cable clutch is not hard to pull at all. I've found the bike lever on the gear lever somewhat lighter than the PVP setup I've had before. Can't comment on a hydraulic setup. I've never had one, but I'll be testing a friend's brand new PVP with hydraulic clutch in the next few weeks. I'll let you know how that feels compared to my setup.

As for the single radiator, it's a two-core unit and the side tanks have the spoon type internal deflectors you see inside Porsche 928 / 944 radiators. I understand that slows the flow down inside the radiator cores for better cooling. It ran at 75 degrees under race conditions with ambient temps close to 30 degrees over here, so no problems yet, even when I jetted slightly rich. If you look at the pics you'll see I have an extra air intake on the righthand side pod feeding cooler air to the carbs and engine. I think that helps a bit with cooling also.

Hope this helps.

Cheers,
Pierre.