KA100 Tips, Tricks and Tuning

For those of y’all who have been running the KA100 engine over the past few years, what little tips and tricks have you started to implement. Anything from a tweak that makes it run better or something that is crucial to the performance of the engines. Very interested to see how everyone does things slightly differently.

A list of the 3 most important things I’ve found over the years.

  1. A good compression tester. Snap-on makes one of the best.
  2. An EGT (exhaust gas temperature gauge). Very important; you need to learn how to use it!!

It will all depend on who you talk to as for what they do. And in the experience I have had with it this last year, everyone is right. I’ve heard that you can “lug” it by using the low end to pull the corners, but I’ve also heard to let it rev. I’ve done it both ways, and since I’ve gotten the motor back from P1, I tend to let it rev more since that was his suggestions.

As it was mentioned, make sure that you have an EGT sensor on it, this will help tune the carb after your on track sessions. Depending on where you are revving the motor to, will depend on what temperature you want the EGT to read. If you can get comfortable doing so, you can tune the H needle on the carb while your on track.

The biggest thing is to make sure it gets.broken in properly per the manual, unless you are buying a used or “blueprinted” motor.

What EGTs should you be looking for?

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If you’re hitting 16k rpm, then around 1200. Drop about 100 degrees for every 1000 rpm drop. Also depends on which sensor you are using. The Heavy Duty sensor (one with a 90 degree bend) read about 100 degrees hotter than the straight one.


I did a bit of a cleanup on the topic so we’re answering the specific question asked.

I ask that we review our responses before posting to ensure they are relevant to the specific question being asked. This includes verifying that advise given fits within the rules of a class.

That’s a hard question to answer. Much much harder than it might 1st appear. Surprisingly, air density can affect it, as well is the fuel being run and the compression ratio of the engine. The distance from the piston face to the location of the probe can have an effect. Different probes can give different readings.

When I was advising drivers on what temperatures to expect, I always said “as high as possible”. If you go too lean, the fuel can start detonating and the EGT will read a lower temperature. When you see that, on the top end, just open the high-speed needle a little. If, coming out of a corner, the EGT reads a lower temperature than the previous lap, open a low-speed needle just a little. It’s a little more complicated than reading the CHT, but the rewards are much greater!!

Tuning is tough. (Al Nunley)

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What is EGT an acronym for please? Idle curiousity.


Great question.

Exhaust Gas Temperature

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Like Michael said, a good gauge is looking at EGT vs. RPM. We run a little colder than that for EGT, but at 16k I’d say we’re shooting for 1150° to 1170° (in freedom units, of course). You can run them over 16k, supposedly someone dyno’d one all the way to 17k+ and the engine was fine, but I wouldn’t go that high on track.

Other things to note, the gearing is closer to a 4ish tooth range that will give you the same lap times on a track rather than a set “ideal” gear ratio, but you should pick from that range based on how you plan on racing. Tighter tracks may want to go to the higher side of that, higher speed tracks might be better raced on the lower side. Your engine builder will also probably tell you whether the motor is better with higher revs or has more bottom end.

Carburetors are the big thing on these engines too. I would replace the gaskets every 3-4ish hours or so. That will help a lot in keeping the engine running well.

The top end also drops off a little after 8ish hours, so if you’re getting competitive and want that edge, that’s when I would recommend at least having the builder look at the piston and ring. If you’re just running laps or not too worried about the slight competitive edge, you can run the engines a lot longer. If I remember correctly one of the Australian drivers on here put 40 hours on the engine before it finally gave out, and I’ve seen people put 20 hours on a motor in a season with no rebuild and it still looked pretty solid.


Is there a specific EGT sensor that you would recommend and how would you recommend finding the correct temps for your specific engine and rpm band?

Would you also mind elaborating just a bit on the gearing for the KA100’s a bit more. Where is a good place to start and what direction do you tend to move from a higher speed track or a much tighter track?


Updated link

Remo is the Importer for Australia. His website and his facebook page also has some good information from time to time.
I am not connected to them in any way.

He posts shots of his Mychron occasionally showing engine RPMs temps, etc. which can show some interesting stuff. He also seems willing to tell people outright what setting he uses for his engines, and for an old bloke he can still pedal pretty well, he just won the Victorian country series which gets 200+ entrants to every round.


We typically run about 3 teeth lower than a Yamaha can, I think it’s a couple teeth higher than an X30.

For example, at my home track we run between a 10/77 to a 10/80 if I remember correctly. I haven’t run there since June or so. However, Badger Kart Club is a tighter and more technical .75 mile track, so we run closer to a 79 there and spin the motor to a much higher RPM. I tend to start a little higher on gear in general but that’s personal preference.

I just use the AiM MyChron EGT sensor, ours are about an inch away from the edge of the fins on the KA. The position of the sensor will change the readout you get.


Aaron, I am picking up a KA this off season. What is your home track? Badger is mine.

Badger is my home track, or at least where I started. I live in Indy now and don’t go back to Wisconsin much.

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Gearing all depends on the track you run on. At the last round of the TSRS at Speedsportz, I think the difference between several of the competitors was in the range of 6 teeth different. There is no magic gearing for the motor because it has a wide torque band and can pull most anything. If you get a motor from an engine builder, they will tell you where the “sweet spot” is. At that race, we dropped 6 teeth from the first practice to the final, and it was just her settling in more. At HCKC we’ve ran as low as a 10/87, but usually on a 10/85, whereas Speedportz we ended up on a 10/73. Since we run on the same tracks, just hit me up for a good starting point.

As for the EGT sensor, it doesn’t matter. There are 2 that work with the MyChron, the standard straight one and the Heavy Duty one with a 90 degree bend. The Heavy Duty does read a little hotter than the straight one. I use the Heavy Duty one, but that’s because when I was installing the standard one it broke on me.

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Anyone have a KA100 power curve that they could share?

Can someone help clear up some Carb confusion?

The KA has a specific part number for its carb (HW-33A) however all of the maintenance items are the same part numbers as the X30 carb (HW-27A). It appears that the only different part is the butterfly and I would suspect the main body. So, do I have this correct, the carb repair kit (diaphragm and gaskets) are the same for either carb?

That would not surprise me one bit. It seems Tillotson uses the same basic Pumper Design for several of it’s Carbs. My old 09 Leopard (HL334AB) uses the same gasket kit as the X30 (HW27A) as well. I think Tillotson just changes the specs on the fuel passages, venturi and bore to suit the requirements for air/fuel delivery. Since the Pump on top of the carb has a Diaphram that works by pressure differential it only allows enough fuel to pass through the main needle based on the difference in air pressure passing through the carb (lower) compared to the atmospheric air pressure (higher), it should not have to change until you get to an application that exceeds it supply capabilities.

“If it ain’t broke, don’t fix it!”

I have a different theory (read my sig). Fuel flow is dependent on pressure differentials, the pumpers, once past the initial start up, do very little. If anything! I base this theory/assumption on the fact that I can’t see that needle going up and down, those flappers, that pumper, that metering diaphragm being able to move that fast. I’ve heard stories of reed valve engines losing their reeds and still running quite well until until the race was over and it was discovered they were gone. I don’t know how true those stories are, but they make sense to me.