450 superkart

[Alex Granelli]

How do the 450 superkarts compare to their 250 counterpart? I read somewhere that they used the ktm 450 in a UK superkart series.

thanks

[Ian Harrison]

Hi Alex

There was a big push a couple of years back in the UK by a particular individual/company to encourage growth of the 450 4-strokes.

Various makes were tried, but the KTM 450 was found to be best suited to Superkart use (least issues). A stand alone series was proposed with limited tuning, to help reliability and agreed for this year, but although the numbers rose to a total of 6 at best last year, and in spite of the "dangled carrot" they have fell to just 2 this year, the series was never actually instigated and the promoter evapourated from view.

Let me just declare my bias!! I hate 4-sroke karts with a passion.

The straight line performance is fairly comparable with a 250, but the braking zone is longer, the cornering speeds are lower and they tend to have fried the tyres by half race distance. This is due to a combination of engine characteristics and weight positioning (C of G)

Also, if the engine blows, dropped valve, cam chain, rod. The engine is effectively totally destroyed and consigned to the bin. Shortened service intervals for valve train items is vital.

A high quality slipper clutch is an absolute neccessity. Otherwise an enthusiatic downchange destroys the motor.

The main "regular" problem (with the KTM's) appears to be head gasket and cooling related.

Best Regards

Ian
_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

[Chris Reinhardt]

Ian, having personal experience I would respectfully disagree...

The most built 450 is just about as fast as a good 250, but not faster than a great one. It's a not a total write off if they blow up, but it can be very expensive. The biggest issue we have seen was rod failures which will saw the cases in 1/2 if they let go, still not a write off.

Myself and the factory Cobalt ran CRF450's, stock bore and stroke, major ported heads and cams, Falicon cranks and rods. The Falicon crank and rod solved the rod issues, never dropped one. As long as you stay on top of the pistons, and don't lean them out too much, they are very reliable.

The Cobalt won it's class at Laguna, I won many races and set track records with mine, you actual mileage may vary...



CR
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East Coast Super Kart Series
"This is how we roll!"
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CR2 Motorsports
"Home of Cobalt Superkarts"
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[Ian Harrison]

Hi Chris

Luckily I don't have to personally experience a heart attack to know that I don't want one

Just wondered what 450 numbers are like now in the US?

What is a typical grid size in 2012 and what was the typical grid size that you were racing against?

Best Regards

Ian
_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

[paul rees]

I like the Honda CRF450 engine. Runs on Chevron Super pump gas. Change oil every race, every other race change filter. I can buy and replace parts through dealer or buy parts on line all day. Engine weight is 63lb's less pipe and carb. Can be converted to remote start. Easy to mount engine < you can fab your own mount or buy one on line . http://www.youtube.com/watch?v=aEIB4EIxsaE

[Ian Harrison]

Hi Paul

That looks great fun!! and the 450 is probably very well suited to that kind use.

I was of course talking Superkarts and I know that the guys found with the Honda CRF that the high speeds and sustained G forces found in road racing caused oil starvation to the crankshaft, resulting in a big bang.

The other big problem was with destroying transmissions. These engines were designed for dirt, where the wheels would just spin. On a tarmac racetrack with the grip afforded by 2 x 8" wide racing slicks, the transmissions wound up until they burst. This seemed worst with the Yam YZF.

Of course the other attraction with the KTM is that it's just push button start, so if you spin out and stall, it's (in theory) a simple re-start and not a wasted race.

Best Regards

Ian
_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

[alan speyrer]

Shifter karts on dirt? what will they think of next?

[paul rees]

Hi Ian these types of engines are really not set up to run. In high R's for long periods of time . Mostly on off throttle use, lots of piston surface area make for high loads. A Recxluse type of slipper clutch would help the engine .I have this type of clutch, but with zero practice for our race track . I haven't put It on, our events run at a fast pace so swapping out parts is costly for time . On a shorter RR track with short straights it would do ok . I looked at the KTM nice package . There are some guys trying out the lay down Jawa speedway engine, on Alky it makes 70hp. Engine weight is 61lb made for 10 thou rpm's . But it comes down what will live and fit the class and your wallet.

[Ian Harrison]

Hi Paul

Yes. I'd agree with you there. It's the sustained high rpms and G-forces that cause the problems.

As I say your sport looks brilliant fun, but we don't have anything like that here in the UK.

I am familiar with the Jawa speedway motor.

Sounds like you boys have a blast

Best Regards

Ian
_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

[paul rees]

With all the Speedway Tracks in the UK and Europe doing Oval Dirt Karts would be lots fun .

[Ian Harrison]

Hi Paul

I think the shale used on our Speedway tracks might be a bit painful and the barrier rails are very close to the track. But your right, it would be wicked

Best Regards

Ian
_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

[Chris Reinhardt]

[Gerry MacNutt]

The KTMs 450s oil system is unlike the the jap motors and upping the jet to the rods should make it last. Ya they do run real hot so cooling is going to be a big issue. The SX 450s runs a plain cap on the cams so you would need to convert that the a roller bearing set up to live in a kart but that and a CP piston and a better cam chain tensioner should do it. I would think on track that required a lot of direction changes the better drive the 450 would have out of the corners would really be a big plus, and you have to like a e-start button , not sure I would like the engine breaking they have


But are they not the Borg? just look at MotoGP

[Larry Stewart]

Guess I'll throw in my two cents because I run a CRF450X. The motor is as fast as a 250 and I have not had any reliability problems. The overheating problem I'm still fighting. The biggest problem is the kart won't turn worth a damn and I can't drive that well. The fun factor is the same.
Like Ian I can't stand two strokes. Just my opinion. Makes me different, not worst.

[Alex Granelli]

This may be stupid to ask, but are their any other engines that work well in this setup that are found on dirtbikes, etc? CR500? Are guys with the cr250's using a slipper clutch also? My plan is to buy a newer roller and add my own powertrain as a fun project. The plan is to have something unique and use in for a variety of things, mainly to have fun. I really wanted to go 450 and e start to have a easy to use setup, I was even contemplating a rekluse clutch to make the kart very user friendly.