KA100 questions

2 Stroke Kart Engine Forums
21

It’s not about speed per se. The difference between 4 and 2 is how the power is delivered and what that translates into as far as driving is concerned. Watch some YouTube vids of folks racing 4 stroke. You will see that it appears to be all about maintaining momentum and any little mistake costs you dearly, not in that moment, but a few turns later. It really requires a controlled and thoughtful driving style.
2 stroke is a lot more “let er rip”. You can cover up small mistakes (to a point) with throttle.
Soooo… if you have ambition to be a good racer, you will be better served learning how to drive well in 4 and then taking those skills to 2 and being the guy that is fast and controlled.
I started karting in 2 stroke and I can safely say that I would likely be a better, more strategic driver if I had started in 4.
But to answer your question… at etown I hit 63 on the straight and 72 at NJMP. Last I rode a 4 was at OKC (fun!!!) and I think in the fast bits I was in the 50’s.

Do not underestimate how much you need to spend in 2 vs 4 as well. 100cc 2-stroke seems more economical than 125cc TAG but it’s probably way more costly in a variety of ways than 4 stroke sealed engines that get literally thrown away after a few seasons.

Here’s an example of 4 stroke racing by the son of one of our own. Notice the general lack of drama.

22

Generally speaking the chassis you get for your 206 will be just fine for the KA. In fact I think some brands have the same chassis put forward as a solution for both. The only difference is with the KA you’ll move your sprocket carrier for your chain drive to the outside of the axle, and add a cradle to support the exhaust pipe.

“probably”. Depends what they mean by a shifter chassis. One thing about shifter chassis is they typically have front brakes which you cannot use with a 206 or KA. Sometimes they can be a little harder to tune for a lower power kart, but it varies. Since you have a good budget, I think I’d go for something that’s intended for single gear classes.

23

Well you’re definitely at the right place, I know that much. Theres a lot of super knowledgeable guys that can and have been helping you out.

We’ve been running the KA at our club this year and it’s been pretty solid all year long. I don’t think i’ve seen anyone run into issues with their motors.

Being from Utah I know MSquared is nearby, I’d recommend getting a kart from them as they’ll have support for whatever you need, and they’ll know what to set you up with.

Maintenance wise I would say rebuild the top end every 8 or so hours if you’re going to be competitive, but while you’re starting out I would just run the motor and get as much time as you can on it. The rebuild is only worth probably a half second and at first that money can be put towards more permanent costs in developing your driving. You could probably go all year before rebuilding when you’re starting out.

Blueprinting isn’t super critical, it’s essentially a little carb and timing work. Once again, for starting out in racing I really wouldn’t go for it. The only reason I did it is because I wanted to be very competitive this year and don’t know anything about motors so I paid the money so I can trust my engine isn’t going to be a problem competitively.

$4,000 should be plenty to get you started. I think I was maybe half that for my first kart, so you’ve budgeted very well for yourself.

In terms of setup, I gear my kart for 16,000 RPM depending on the track. Longer tracks like New Castle the maximum RPM will be lower, but I’m not sure what’s around Utah to race at.

Also, a couple things to think about between 206 and KA100.

First, 206 will definitely be easier on tires. I’ve run whole seasons on a set of tires before but I’d never be able to do that with the KA. There’s definitely a higher maintenance cost that is coming from the KA and 2-stroke racing in general.

The KA is a very tough motor for new drivers. It has an aggressive torque curve and is a handful to drive at first. The 206 will be much gentler and easier to learn on. You can then take what you learn from 206 racing and apply it to the KA (carrying momentum at least) and be at the same point after a few days as you would have been on just the KA, but without spending the same amount of money.

You could pick up a used 206, run it for a year or two, and probably sell it for what you bought it for after rebuilding it.

Just a couple thoughts on cost effectiveness for you since that’s a consideration for just about every driver in America.

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24

I would generally agree with what James is saying here. I ran 206 cup this year with a DR M99 Chassis which is generally regarded as a high HP shifter chassis. I was able to run competitively (https://youtu.be/wtt6QC1CWFM), however, because of the added caster that 2 cycle chassis have built into them, I struggled with the 206 on corner exit. Most 4 cycle chassis come built with less caster which allow for better rolling exit speeds. If you purchased a used low hp specific chassis, it would likely be your best bet since you can choose either class without sacrificing too much.

From an economical standpoint, I believe the 206 is cheaper and will allow you to get your feet wet. If you don’t end up liking karting, it would be easier to get out knowing you didn’t spend all your money whereas with the ka100 it will likely cost your entire budget once all things are said and done. Since you will likely be purchasing a used kart regardless, the depreciation will not be too bad. If you were to buy new, that is where depreciation hits the hardest.

From a skill standpoint, I would recommend starting in either ka or 206, whichever has more competitors. The more people you run with, the more you can learn from and improve from. I would agree mostly with what @Aaron_Hachmeister_13 said above me as well.

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25

Connor I live in Utah and my son has been racing the UKC for the last 10 years. We have a 2014 TonyKart w/ a Briggs LO206 motor we can let you have for 1250$

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Admin ask - That we keep any sales conversations in DMs, please. :slight_smile:

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27

Reading through this thread and noticing that it dates back to when the KA was very new to the karting scene.

With the most recent comment here being 6 years old, and the KA having since risen tremendously in popularity and prestige, does sentiment about ‘a stock KA being able to compete nationally for wins’ still hold true, or has the engine tuning scene changed to where the top local and national drivers now have engines that meaningful advantages over a stock one?

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Builders have found things to tweak so you definitely would want a built engine to compete at the front regionally or nationally. You’ll be giving some up on a stock engine. But locally or lower level regional racing I wouldn’t worry about it. The parity is still decent out of the box.

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29

Interesting, but I guess not surprising considering how important the class has become. Anyone know the specific type of things that engine builders are (legally) managing to do in order to pull some more power out it? (is all just parts matching from multiple engines, or is there actually some machining allowed/involved)

30

The builders can’t really machine much in the current rule set. There is some magic in what stones they use to hone the bore, the piston to wall clearance they are comfortable with and ring end gap all of which is open to them and part of the magic.

Aside from that if you have mechanical knowledge, a few specialized tools and time on your hands you can read the rule book and set one up that will be pretty close to any of the national builders. Power Republic YouTube videos are also helpful. If that’s not you then spend the money and have someone do it for you, it’s worth time on the stopwatch

Fun story: we setup a stock KA for my nephew (timing / squish / carb) to practice for his transition to Jr next year. His excuse for being off the pace was not having a blueprinted carb. So I swapped my blueprinted race carb for his DIY blueprinted carb and in the next session he went the same speed and I….went .15 quicker on his DIY carb than I had on my carb the session prior. Tons of variables in play there but i can at least say with confidence that carb wasn’t slower.

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31

If that’s true, at least the gains sound accessible compared to piecing together a Frankenstein motors from a whole bunch of them.

Still, if people run at local tracks where the top guys are national and regional players (as exists at my local track), then they’re still going to be subject to getting smoked and now stock ‘isn’t going to be good enough’.

I started asking these questions, because all of a sudden in the last year the top KA times from the top seniors here (at Prairie City, CA) have dropped by about .75 a lap from what has been their historical norm since that package first showed up (several years ago now). I can’t find it now, but I also remember reading something, I believe around these parts, about people complaining about engine disparity at recent national events.

32

Most KA groups nationally run on MG reds which changed this year and got significantly faster. I’d bet that’s where the time is at vs. motors making any more power. I’ve been using the same builder for 4 years who provided dyno charts with his motors and my motors have made pretty much the same power after every rebuild in that whole period. He’s evolved a touch in carb setup to change power under the curve for better raceability but the peak power has remained pretty much un-changed.

The fact that these motors are CNC machined means pretty even parts parity. IT’s not like the days of the old Yamaha’s where this casting run in 1982 was better than that casting run from a different country in 1986. That’s not to say there aren’t still monsters out there…I raced against a couple of engines this year that were clearly “better” than mine…but 95% of the time I don’t worry about motor performance as long as I"m doing my job with chassis setup and driving.

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33

KA has good parity nationally. Some certainly are better or worse in different parts of the powerband, but they are all pretty close when built out. And as noted, the difference in a stock to built engine isn’t that big that people will be “getting smoked” necessarily if they aren’t blueprinting.

As Andy said, the new MG Reds are worth 0.5-1.5 a lap depending on track.

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34

This is totally mind blowing. After I posted, I almost mentioned that change as a possible explanation, but didn’t want to salt any responses. I haven’t actually driven on those tires yet (going through old stock still, and a 9 month layoff didn’t help, lol). Based on some other stuff I read, I 100% buy that the tire change plus elite-knowledge of carb/jetting can explain most of the extraordinary gains in KA performance at the very top of the field this year.

I’ve got to give it to this engine package - it’s really impressive. If you have a 125 TAG or an 80 shifter and are anything less than a really good driver on a reasonably well tuned kart and decent tires you just might have a KA or two blasting past you on practice days. It punches above it’s weight for sure.

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35

If you are on the old tires, you will be substantially slower than those running the current tires. As others have said, we have seen people running anywhere from 0.4 to well over 1 second per lap delta from last year.

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36

My laps at the Stars race in Mooresville were 1.0 faster than I ran there when I won in 2018 on the old spec tires. And I was mid-pack at the Stars race. The leaders were 1.2-1.5 faster than I went in 2018.

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37

I think your ability to compete locally with a stock engines depends on the quality of your local club. At our club, you need a pretty strong engine to compete. Thankfully, we have a technical track and you still need to be a good driver to compete. I’m not sure how many people are buying stock engines anymore. They usually buy from a builder who at least tunes and dyno’s the engine.

38

Our club races are strong 206 fields and intermittent KA fields. We podiumed at several this year in our first season in KA. Our regional KA fields are large and very very tough. We didn’t finish above the top half in any of the TSRS races this year. :woozy_face:

Carb tuning is where I have seen distinct advantage between teams at local and regional. Having someone available that knows how to dial the carb for the track size and air conditions is worth well over 1/2 second. Experienced that first hand this year. We went from 1.5 seconds off the leader and 30th place pace in practice to qualy at 0.3 off of 1st, 0.2 off of 3rd, and 12th place overall. Only change----carb adjustment.

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39

I think your carb would have to be WAY off to make it worth a half second. Like not running properly. Even with EGTs 100 degrees off, I haven’t seen a half second swing in carb tuning.

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40

Same, some drivers bring engines from england or contract an engine tuner from another cpuntry for their son.
Doesn’t help our track isn’t very technical.