After reading through the vintage 100cc thread and discussing some of the twin engine wacky racer style karts I got to thinking:
Who has built an “unlimited” style kart where the goal was simply to see what was possible. Does anyone have interesting stories or photos of some wild karting builds where rules didn’t apply and money was no object?
It is interesting to me that in sports cars this is very common but not so much in karting. If anyone can include lap times for reference that would be awesome as well.
BRC Unlimited Enduro comes to mind, but I’ve never heard what times it was capable of around a circuit. Has anyone experimented with a fan kart or tunnels for downforce?
Well, it depends at which point which venture outside of what can be considered a kart. You’ve got drag karts, the Gixxer kart type thing. Riley’s twin BRC150 is bonkers. Matt Hamilton used to race a KZ with a 100cc on the left side.
I was thinking more like circuit style karts for road courses or even kart tracks. Jim Mcclure had that jet powered kart but I heard it never really did the speeds they claimed it did.
The Riley Twin BRC definitely comes to mind regarding this topic. Funny though how little there is compared to sports cars given how cheap karts are.
I used to see a fair bit, but as karting has become relentlessly kid focused, as well as homogonised, the kind of eccentric adults you need to attract don’t really see karting as something you can do this kind of stuff with. Some of the laydown stuff is cool though.
It is an interesting question. In my mind it’s something like the following to be considered a kart:
-No suspension
-4 wheels
-max wheelbase of 1200mm
-max width of 55”
-no differential and single piece axle
-no power steering
-max wheel diameter of 6”
With this in mind, I feel like KZ karts really aren’t THAT far off from what’s possible. Of course experimenting with non-homologated frame designs, more powerful motors, and gumball tires would be the first changes, but honestly I think it would still be skill limited very quickly. As it is most drivers aren’t getting the most out of MG yellows until the regional level.
Bringing real aero into the mix could make it spicy.
My latest build getting closer. Taken way too long and the seat fitting has been problematic given the lower orientation of the fitted seat and my height at 186 cm (different clutch handle required and some alteration to the steering to create leg room). Due to have its first run on 4 May at Broadford on which I’ll post separately. Rather hoping I don’t blow it up at the first meet, but them the risks.
I’m just using a standard KR KZ chassis, but otherwise lots of Superkart bits. Open 125 is the class, so a new TM R2 with an Anderson digital ignition (BIG spark) and separate power supply, 39 mm Dellorto and running a 220 main jet (so lots of fuel). The intake manifold is a special CNC and the boot I believe comes from a standard 250 twin. My builder did look at changing the primary drive but didn’t quite work, so sticking with standard gearing. I believe the sprockets will be 21 front and 21 rear. Top speed at say Phillip Island into T1 should be over 190 km/h (118 mph), some say closer to 200 km/h, but we’ll see. My Stock Honda peaked at 180 km/h. Will be puckering for me and above my pay grade since I’m not meant to lift.
Alan Dove pointed out a key reason why. For the past few decades, North American sprint karting (karting on paved kart tracks, under a mile, with left and right turns), has primarily adhered to the CIK/FIA Euro format of karts, (especially when it comes to chassis), and kart racing. That means a laser focus on the younger, under 18, racers. Particularly the very, very lucrative subset of karters looking to make a career in race driving and eventually move over to racing cars in the future. In short, a “stepping stone” to car racing.
But aside from the career-minded kids in karting, possibly the biggest reason a lot of adults (and admittedly some of the children) race karts is the supposed value in karting compared to other forms of racing. They want a place for competitive, relatively inexpensive, wheel-to-wheel motorsport and karting, in theory, better provides that than other venues. They do not want things complicated by expensive technology and development.
But that also follows the trend in auto racing in these days, more “spec” racing and less tinkering in general, for a variety of different reasons.
The two segments of karting you’re more likely to find more unlimited examples of karts are Dirt oval kart racing, and Long Track / Road Race karting. Road Race karting even has a class named “Unlimited”, but even then, they adhere to a set of rules that keep it strictly a go-kart.
It not a coincidence that both Dirt Oval and Road Race karting are not as “professionalized” as sprint karting has become, Still a lot of karters pitting out of a truck and/or small trailer, and not as many tractor trailers.
What kind of power are those quad engines putting down? I’d love to see how fast an enduro could go around a track like Willow Springs with 150-200hp.
Really cool replies. I agree with the gentleman above who listed some basic parameters of what makes a kart a kart. My thought is kind of throw the rule book away and then go to town on a traditional 250 Superkart.
Makes sense why it has got away from the hot rodding side if it has become more of an institution for getting to the next level. I’ve worked as a coach in the sport in the past and do enjoy the accessibility karting provides myself and others.
The power to weight ratios of these machines is really what appeals to me about karts. Have never driven a shifter to this day…want to badly. Agree about the skill becoming the limiting factor. Every time I drive a TaG I am reminded what real cornering forces feel like.
Tom: please update with a video when you run it. Would love to see that.
You’re tire limited on total lateral force before your sidewalls fold over. So with F=ma and cornering speed dominant over straight line acceleration, I’d say something like an OK engine on a cadet chassis with a small (45 kg) driver and an effective ground effect tunnel would work best.
By the way, we’re ready with both powered and unpowered options when ground effect is allowed.
I can’t find it anymore to link to, but I remember the 250 superkart time at Willow was around 1:16’ish, which means that only the upper echelon of purpose built race cars/prototypes went faster.
Here’s a an article about Eddie Lawson’s (4 time 500cc World Champion) times in a 250cc superkart at Laguna. 1:23.875, which again means that only race-specific cars/prototypes are going as fast or faster. And that was done 20 years ago, so I imagine with a little more technology in the mix a superkart could do even better than that.
Those are both extremely fast times at Willow Springs. Very impressive. Formula Mazda and Super Karts have to be the best value for money in the world of racing.
A lot of what’s possible will depend on the track of course. On most sprint tracks, a KZ with the right driver is close to unbeatable. Even with a twin cylinder 250cc engine, the KZ just seems to me the most efficient way to get around a sprint track.
The downside to a gearbox kart of course is the time lost to shifting and the extra weight if the gearbox etc.
I think an Aixro XR50 running methanol, set to kill with a CVT would be as close to the best balance of power and weight as you can get.
I believe C-open in vintage might be a little faster than KZ at NCMP?
James - I have heard that is true on sprint tracks with regards to KZ. It must be that overall weight, not just power to weight is instrumental in producing fastest laps on those types of circuits. Reminds me an autocross course in that sense.
Aixros have peaked my interest for a number of years due to the performance and rebuild times. I heard they were melting seats and that kind of deterred me from keeping them on my radar. Have people found a fix to that with heat shielding? CVT would be a great solution. I wonder who makes a good one. They are junk in the automotive world typically.
Aj - that is pretty fast compared to a KZ2 especially given the lap was only 30 seconds. Thanks for the information. This thread has given me some good insight.
I know it’s Easter, but JESUS Rob. That looks like so much fun. The last shot with the front end coming off the ground is so cool. I lived on the east coast and did a little dirt oval in a clone one night. Other than the boringness of going left with no one else on the track it was extremely fun.
Did you guys have tear offs back then or did you just grit it and go blind?
I’ve been considering mounting a couple Castle 1717 motors to the front wheels. These are normally used for RC cars. I think I could get the entire system in about 10lbs with batteries. Each motor can put out about 6hp (4.5kw) at 155amps. I want to use torque vectoring the same way the newer Acura NSX does.
I already have the speed controllers, motors, and batteries. I would need to scan and design a mount and gear assembly for the front hubs and then a throttle control. The Castle software has some really nice capabilities with Regen breaking, torque curves, and breaking.
