Looking at chasing KA100 SR next year. Have 17 months of racing under our belt.
A few considerations we are looking at:
1). Finding the LO206 class to be a bit rougher driving than what we see in KA100. The draft is so important in 206 that guys pack drive like Talladega and Daytona, and we know how that ends up!
2). More less skilled and rookie drivers in LO206 means if you find yourself at the back for some reason (DQ, breakage, wreck) you are surrounded by very erratic and inconsistent drivers.
3). My kid wants something more challenging to drive and like all drivers, wants more speed. 
4). My son is very tall (6-4) and has convinced himself that the higher power KA won’t penalize him for his height when grip is high as much as 206 does.
5). Is LO206 really that much cheaper than KA100? Maybe, but I am not certain we are saving that much trying to find and keep those last 1-2 tenths anymore.
6). If we go KA100 we will drop our 18 race club schedule and focus on regional series. This year we will do 22+ race weekends. Next year we will run about half the weekends.
Not sure where you race locally, but just note this is probably the opposite regionally and definitely nationally. KA is a very aggressive class most places.
While I have not raced beyond local with KA or 206 I think you need to look at the whole year for costs. To be competitive with KA you will likely be doing a top end every 6 hours or so and bottom end every season, maybe 2 if you are running only 11 races. You can buy a new 206 for the cost of a complete rebuild on a KA. You will need to buy race fuel and 2T oil. We are paying about $20 a gallon for race fuel and the recommended oil is $20-25 a liter. I believe the KA uses noticeably more fuel than the 206.
Yes KA is faster but they are as equal as 206 and you will encounter much of the same driving styles that you are hoping to maybe avoid. It also appears that KA has become the stepping stone to TAG so you will encounter a lot of younger drivers that prioritize winning over staying clean.
You may want to jump right to TAG but that will surely be more expensive. However, It will likely be the class that penalizes height the least.
@tjkoyen Much of this is based upon NTK experience. With the high grip surface and three banked corners it is not my favorite LO206 track. The pack racing produces off’s in those very high speed sections on a regular basis.
In our regional racing all we have is KA100 then shifter, so only 1 single speed 2 stroke class really available. The other 2-stroke classes are run in varying numbers at some club races.
All of our plans are subject to change if we can manage some seat time in full size cars. He will gladly trade 2-stroke karting for some endurance racing in a full size car. 
@mtbikerbob
I know we will use more fuel. At club races we burn pump gas, but all the regional series make us run the same expensive canned fuel as the 2-stroke guys. So we aren’t going to spend a fortune more on fuel if we only do regional races.
As for tires, we aren’t going to be hurt much at regionals either, as they require you run the same set for the weekend in 206 and KA. So we practice on a set and race a set now, that won’t be changing for KA. Now if we club race a bunch, the tire difference will be huge.
Motor costs and rebuilds are the big one that I don’t know what to really expect!!! I see guys doing top ends after every race weekend, every other weekend, and some that do 1 top end per season. Bottom ends, I figured 1 per year or so. I am pretty strong mechanically, so the carbs and top ends I may do myself, bottom ends will go out to someone. I know its more complex than cutting seats and lapping valves on the 206… 
Like my response to TJ, KA is our option for 2-stroke regionally. We aren’t quite ready for national level stuff yet, so KA or 206 are our choices in karting. We have a potential opportunity to get him in some full size endurance racing. If that works out, we may stay 206 and kart a whole lot less so we can afford big cars.
Just want him to keep making contacts and see what his options are in this world. He wants to be around motorsport in some form, even if it isn’t behind the wheel.
A bit of a re-direction but this might be of interest:
Has he test driven any two strokes yet? Since NTK switched us to the Evinco Blue, TaG and 100 are running pretty close lap times. Weight being the biggest factor. He is welcome to take a spin in my kart. Given we are close in height the seup should suit him. The seat might be a little big, though.
So I’ll report back on my experiences, for better or worse. (Buckle up Buttercup) 
RacerParenting got the best of me last weekend, as Dad spent 99% of his time getting the girls on track (Wrenching, parenting, corner working, stressing, etc)
So here I am with this X-30, with zero practice sessions, hell- I had never been on a 2 stroke before. But I decided to sent it anyway (not advised).
Takeaway #1: Holly piss, this thing is fast compared to a 206. The power band is all over the place (comparatively, just when you think you’ve hit the limit or the power band, it has ANOTHER gear so to speak) Which is very tricky to manage. As just when you “think” you know where the power is going to come in, the goal posts move and your white knuckling the living dawg $hit out of it trying to understand (in real time) what to do with all this power. (Again- coming from 206)
Takaway #2: WTF was first reaction when trying to estabish my racing line. (Not happening) The corners were coming at me so fast, it took everything I had just to keep it on track. What is a racing line again?
Takaway #3: (see takaway #1)
I had alot of fun (sort of) but jumping into a established 2 stoke field with no experience was sobering. I placed P-9 out of 14: but to be honest 3 DNF’ed the first lap, so I really only beat one person.
Sobering experience, but experience none the less. Still learning . . . still trying to process it.
Glad I didn’t read this in the morning while drinking coffee.
so…let’s turn the perspective around. If a 4 stroke costed like a KA (all in: engine price, maintenance, tires…everything). How many of you would pick the 4 stroke over a KA and why?
Good question! I did not get in 4 stroke because of cost. I grew up on KT100 went off to cars and came back to great series called Ignite by Margay. Kart count won the day for me. Now if you add equal participation I would always go 2 stroke. They are just cooler. This year I have also started racing new Margay class called Ignite 100 that is spec and uses VLR100. That all said I find I really like the 4 strokes also. So now I am running both
Having done both it would be the KA all day. I would say speed would be the first reason, and the second would be that comparatively the KA is a little more forgiving for sloppy driving at least compared to the 206. Third, did I mention the speed? I also think the KA is easier to maintain week to week. I didn’t realize this till I owned a 206, running on pump gas creates more work than expected.
I think Robert hit the nail on the head, you cannot be sloppy driver 206, you just don’t have the power to get you out of a mistake. I litterally watched a 206 this past weekend where a guy was in P-1 with about a 60 foot lead. He lead the race from Lap 1 to lap 11 of a 12 lap race. He made one mistake and over cooked a corner, and finished P-4.
I will always be in whatever class is the biggest. I like kart count and competition. If there were 30 KAs and 10 206s, I would be in a KA. But right now, at our local club there are 30 206s and 5-10 KAs.
100cc all the way. I loooooove 4-stroke but powerband is everything. In an ideal world where we didn’t have money to consider, or field sizes, ka100 all the way.
Reality= I’ll stick with 4-stroke
I guess it depends on the four stroke exactly because once you get to that power level the “206” like maintenance is no longer a thing.
Generally, even though I love two strokes, the additional work with fuel mixing, carb Mx etc etc is not worth it with the KA.
If I can bang gears with the four stroke that’s a bonus too.
All that said, if the grids are the largest with the KA I’d probably just deal with the two stroke stuff.
LOL, I hear you. I though was crazy enough to just start with a shifter kart and learn how to drive one-handed.
Think faster…
This. I have a KA that just sits until the local KA Masters class grows bit.
I would argue the 206 has more additional work but only if we are talking about gas with ethanol. Either I didn’t ask the right questions or talk to the right people before I bought a 206 but I was shocked at what I needed to do; Clear the lines, fog the carb with wd-40, empty the tank, empty the bowl and drain the oil, plus these are all kind of messy jobs. And for the most part carb settings are about the same in both, set it and forget it.
I’ve found that the “be locally competitive” budget is identical in KA, X30, and shifter. What you save on engine rebuilds is spent on sprockets, chains, pumper kits, and crash damage. New tires for qualifying are necessary in all three classes. If we had bigger shifter fields, the entry-level engine would just be a ten-year-old engine rather than something making half the power, and there’d be larger production and sales volumes on those engines. I agree with you that 206 racing is much less expensive, mostly because of the reduced driveline and chassis wear.
Is there any good 2-cycle driver that’s not in “competitive in a completely different sport just because of their fitness” shape? A midpack KA100 driver might get away with a training regime that would have them unable to climb out of a shifter kart after the feature, but strength and endurance are necessary advantages in every class.