Road Racing KA-100 Sprint Kart

Thinking of road racing my KA-100 OTK, end of Oct at Attessa, car track in AZ. I think the gearing will be somewhere in the 13:65-68 and I think the weight is 360lbs. RR events are standing start, so I’m somewhat concerned about the clutch. Also, the events are 30 min, I’ll be running a O-Ring chain. Any other insight would be appreciated.


Clutch should be okay, as its rather overkill for the KA engine anyway. Did several road racing events back on the HPV/KPV platform and even those Horstman clutches held up just fine.

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At our SWK events we do a rolling start and we usually do the weights using the drivers weight, not the kart and driver together. You’ll be fine at whatever you come in at.
We are pretty easy on rules.

And now a little something about the classes we run.

We line up by you best lap in Practice/Qualifying (all laps are timed).

All karts run at the same time but are scored separately.

We have four classes. Fastest first.


250 cc twins and singles, 450 cc four strokes and other “exotic" karts.


125 cc adult modified gearbox karts. ICCs run here too.

SPEC 180

It’s for people that are about average weight,

And have a Stock Moto engine.

If that’s you, then this is your class.

When you sign in just put SPEC on the sign up sheet.

We’ll still have our other groups.

This class is intended for “Stock Moto” gearbox engines and average weight


Weight (Note: We’ll use the honor system until there is a problem)

· The driver shall be weighed in his/her driving suit and driving shoes,

but without helmet, rib vest, neck collar, gloves, or other driving

equipment. Driver weight shall be 180 pounds minimum.

· If the driver is less than 180 pounds, he/she must have ballast

mounted on their kart that will bring the combined weight of driver and

ballast to 180 pounds.

· The mounting of ballast shall comply with existing safety practices.

· Drivers may not carry ballast on their person.

· The ballast used should be easily removable for total weight


· The weight of the ballast shall include mounting hardware only if that

is the only function of that hardware.

· The weight may be marked by officials after verification.

· Driver weight may be checked before or after an event.

The scale for each event will be a bathroom scale.

We care about how much YOU weigh, not your kart.


All adult electric start, one speed karts.

Other adult karts may be included depending on performance.


The class consists mainly of Briggs World Formula powered Sprint karts.

Three weight divisions.


Driver weight less than 160 pounds.


Driver weight less than 160 to 190 pounds.


Driver weight more than 190 pounds.

Class selection may change based on driver performance (see race director).

The Challenge class includes other, slower performance karts.

Hopefully good judgement and common sense work here.


What is the weight for TaG? Is there a different weight for 100cc vs 125cc TaG?

At this time we don’t do weights on our classes except for the Challenge classes - and that goes by the driver weight. When participation shows a need for it we will respond. 100cc TAG is pretty much an unknown performance wise compared to a 125 TAG. I don’t think running lighter could ever level the field between the the two - especially on a big track. So leave your weight at home and come out and have fun!


I went Road Racing last weekend with my KA100 sprint kart at the Attesa track located near Casa Grande AZ. The track is 2.3 miles long with a 2800 ft straight and is very flowing and very very smooth. I don’t think there is even one bump on the track. I hit 84 MPH (according to my mag sensor) and the average speed was almost 70 MPH. It’s a very different experience. Sprints the mode is attack with RR the mode is delicate. Also, sprint racing the fear is losing a tenth or two, whereas with RR the fear is more of a physical threat, which might go away with more track time.

For me, it seemed like the KA100 was not motor for RR, I think a Rok or X30 would be more suitable. There is only one TaG class, so I was running with X30s. This group is laid back and everyone is enjoying the visceral joy of karting and yes of course there is a competitive air about but probably not as important. The karting group runs as a session with cars, so its a mix of LO206 both single and dual, TaG, mix of single speed karts and shifters. There were more incidents than I would have expected on a big track with karts.

For RR, I replaced the stock clutch with a carbon shoed version and ran a 13:75 gear. Both ends of the kart were fully narrowed, rear of the kart was lowered and the caster set to minimum. We had 20 minute sessions, 3 practices and then a Main I changed the setup during practice a bit by taking out all of the toe and moving the steering links to the upper holes in the steering column, as the initial turn in was a bit touchy.

It was a blast, so I think I’ll try it again but with a water cooled 125 cc motor. Rok or X30??

Sorry no video.


Interesting observation.

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Given you are averaging around 70 mph and you peaked at 80 mph, I might suggest the X30 over the Rok GP. Don’t get me wrong, I have a Roc and love it, but as I understand it the X30 has more top end and Rok more midrange. I would expect on a long flowing road course having more top end would be more advantageous than midrange.

Greg – I purchased a used Rok because it has more HP than the X-30. The others all have X-30s, so we will see. The Atessa track had very fast corners and a 2800 ft straight. I’ve always though that the X-30 is better for point and squirt tracks. There is an interesting article comparing the X30, Rotax and Rok.

This site also has reviews on the X-30 and the Rotax, makes for interesting reading.

I’ll be taking the RoK setup out for road racing for the first time in 2 weeks, so if you have any suggestions for road racing or in general, I’m listening.

I’m hoping that my competitors are not reading this. :grin:

Thanks – Larry

It sounds counter intuitive, but generally mid range is what you want for road racing due to the higher average speeds.

The majority of the power is in the engine’s midrange and you need all of it to push the air out of the way at those higher average speeds.

Rotax is very strong in road racing for this reason.