2 stroke chassis in 4 stroke karting

So the 206 scene is a trip. Lots of gimmicks for people chasing a few tenths. So I got my start on a 2 stroke chassis with a pretty soft/ flexible frame, and I was told it would never work in 206 as the chassis needs to be stiff. I’ve been on potium a few times on this set up, more on the local/ regional level and not on the national level.

I have see and (known) people who lead the pack in 4 stroke fields on 2 stroke chassis’. Granted its not the norm, but several people seem to make it work for them.

Fast-foward 3 years and I finally mated my 2 stroke chassis to an X-30. But I want to run two classes (X30 and 206), and I came across another deal on a 2 stroke chassis I plan to build as a 206 kart.

So I’ll yield myself to the experts- what is the best method to run a 2 stroke chassis and make it competitive in a 4 stroke field?

My initial thoughts are to stiffen up the chassis by adding a hard seat, and a hard axle. Is that the right way to go or are there other factors I should be considering?

Here is the chassis I’m playing with. Its a 2021 TB Kart S586 that I plan on mating to a Stewart Racing 206 motor. I just pulled all the 2 stroke parts off, so now I’m working with a blank slate so to speak . . .

As always, I appreciate the input from this forum as you folks provide an education you cannot find in most circles.

This is my fourth TB Kart:

(2) TB Kart Monster Cadet Karts (LO206)
(1) TB Kart (European) S-55 (L0206 turned X-30 kart)
(1) TB Kart (American) S-586 (Deticated 206 Kart)

Too many karts I know, I think I have a step class in my future . . . :rofl:

But here is the S-586 I’m working with for reference. Scored it off a factory race driver and it only had 4 sessions on it. Being a factory driver, he had nothing into it and sold it for stupid cheap.

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How do you find so many TB Kart chassis?

TB Kart is out of Europe, but TB Kart USA is out of Florida, so they are known and/or available in my backyard? As are Birel, and Tony Kart. Every locale’ is different.

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I ran a T5 axle and a fairly soft seat in all my TB shifters.

I’ve always liked a medium axle and a soft seat in my Euro style chassis for 206.

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There’s really no rule of thumb because (arguably) two stroke chassis and a four stroke chassis are not really a thing in the way it’s sometimes said. It’s a very subjective and varied difference. A “four stroke” chassis could be a different cross bar to accommodate inboard drive better, it could be a more economical model with less adjustments and less magnesium parts. But overall there are more similarities than differences.

All that said, having worked with a 32mm (Wildkart) shifter chassis… So, I will say give the chassis what it seems to need and try to not pre-empt too much. Drive it and tune it.

I moved the seat forward, pulled a litter caster and it was pretty decent.

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Set it up just like a KA/2-cycle kart:

Hard axle
Full rear width
Standard ride height as long as you are 5’10” or less

Soft flat bottom seat with leading edge of the seat just behind the center bar, flush with the bottom rails.
Seat struts on

Standard front width
Front bar in
Neutral caster

Good mag wheels (not Douglas)

Then tune it just like a 2-stroke chassis. Unless you are in Canada then throw all that out the door. Lol


Take the KA set up, put the 206 on it and send it.

The 206/ 4 stroke only chassis argument came from when 206 first starting taken hold. All the 4 stroke racing was done on narrow “gold cup” style chassis.

The thought was that was the only thing that works. Had to be 50” wide, 1.25 axle, 5/8 spindles, 1 1/8 or 1 1/4 tubing, 8.75 rear wheels…

People swore a 2 cycle chassis wouldn’t work. Fast forward and nearly all front running karts are 2 cycle in design.


The way I look at it (and someone please correct me if I’m wrong), you can put a 206 on any KA chassis and it will work fine. I race with guys on 2-stroke chassis in 206 and its all the same. But I would imagine it gets questionable if you try to put a KA on a “4-stroke” chassis.

For example my Birel AM29 is made up of both 28/30mm tubing (specifically made for 4-stroke racing) where as the RY30 is all 30mm tubing.

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The only thing I keep hearing from more experienced guys (one in particular, but he owns 10-12 karts, has been racing for decades, in all classes- 4 stroke, X30, Super X30, shifters) is weight and “rotating mass.” He swears that sheading every gram counts, especially on the live axle due to the low power of the 206. I was having the conversation with him and he said (like when it comes to my TB) everything is more robust and oversized to accomidate the power of a 2 stroke engine- especially when we compare it to his must lighter MGM Kart which is his main 206 chassis.

Appreciate the conversation. Cause all I can deduce from my own limited experiences is my old TB Kart S-55 chassis w/ my 206 acts very different (to me) compared to “dedicated” 4 stroke chassis’. Being a softer chassis- It feels faster and flexes better in high speed corners, and to me in tighter low speed sections it doesn’t seem to spring off the corners as good. At least that’s what I noticed when test driving some of my friends 4 stroke karts. I might be over thinking it?

I’ve been rolling a 2 stroke chassis for a while, and it’s been mostly trial and error. Main error was shortening up the rear axle when I didn’t really know what I was doing. Once I brought the rear width back out to manufacturer’s spec., handling improved and lap times dropped.

The tracks I have the most practice on are MCC and G&J, and I’m definitely faster on the more open, smoother MCC track.

I did finally get a 4 stroke chassis, so I’m really interested to see how it compares to my old Arrow.

Rotating mass is typically no different between a chassis with a 206 bolted on or a KA beyond whatever rotating mass the engine and clutch bring with them. You can even make a case that more rotating mass helps a 206 because it will carry more momentum.

Out of a tight turn there’s little to no difference in power between a 206 and a “canned” KT… something to ponder.

Also, a world formula puts out about the same power across the range as a “canned” KT.

In terms of one chassis feeling different from what you have… it’s awfully subjective. As is “soft vs stiff” chassis. For a start, you can have different stiffnesses in diagonal, lateral and longitudinal planes. But there’s an absence

If you’re able isolate variables like:

Spindles (rake, length, diameter and caster/camber)
Kingpin 8mm vs 10mm.
Seat position and stiffness.
Steering geometry Ackerman and toe.
Oh, tires and wheels need to be same of course (including wheel offset)
Axle, seat stays etc.

…. and compare notes that would be one way to go

So to summarize…

Id say yeah :laughing:. But geeking out is fun too. Everyone has a theory.

I don’t know who said it but someone in karting used to have a signature that said “don’t let someone else’s chewing gum get stuck in your thought process”

That is an interesting take. As others have noted the basic chassis design is fairly similar but the American made 206 chassis are usually larger diameter tubing. Maybe not stiffer but larger. Where I see the biggest difference is the rear axle and brakes. American chassis will have a simple solid rotor with simple MCP brakes, perfectly fine for 206, but likely not up to the task of KA or faster. I also notice smaller diameter 30 and 40mm axles. Not sure if they are lighter though.

MCPs work just fine for a KA if you use the 3/16" or bigger rotor and blue pads.

My preference is MCPs with blue pads and a Seay SuperBrake

Its intersting you make this point. Only speaking to the TB Kart, and not my own experiences, but those of someone smarter than me and who has more racing experience than I do.

Last year I had a buddy test 30Mil, 40 Mil, and the traditional (stock) 50Mil axle. He was trying to determine the pro v. cons of each set up. I remember at the conclusion of his “experiment” he concluded the 50 mil performed the best; which is what his TB Kart came with stock from the factory. (interesting)

On the topic of chasing a few tenths in 206, people are trying all sorts of things trying to find cometitive edge. Some for better- or for worse. So smaller diameter (in theory) seemed to be the ticket. But in his experience in the real world, there was no noticable advantage.

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I’ve used a “2 stroke” chassis all year in LO206. Bearing in mind it took me a couple of races to get up to speed in a 206 (i’d only ever driven higher power 2 stroke classes) by the last round of our regionals we were one of the fastest (and I’m old racing against teenagers).

One of our snr drivers won the regional series on the “4 stroke” chassis, but I suspect he would of won it on a mattress with wheels. In Jnr 2 we had both 4 stroke and 2 stroke chassis running at the front.

At least with our frames (Croc), they look like they require different driving styles but the ultimate pace is about the same.

Easiest way is to back to back them, it takes about 10 minutes to swap an lo206 and tires over if you have the chassis ready.


That is a good chassis and it works great for a 206. It is a stiffer frame, so you will need to go soft everywhere else. Soft seat, soft axle, no bars/supports, etc.

So on a softer chassis, stiffer seat, stiffer axle? (The Geat Equalizer)

I just popped for am XL Tillet T-11 seat (removing the OEM medium seat) which I believe is a stiffer seat on an otherwise softer chassis. Hense the question. . .

For context, I”m competing in the Masters Lo206 at 390 lbs.

My chassis is SOFT SOFT SOFT and I run a super soft seat and medium axle.

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That’s thinking too general. Like Burpo said, different karts need different things to work. And even then, driving style or tire or track conditions will change what it needs.

Can’t tune a kart in your garage. Set it neutral, go to the track and drive it and see what it needs.


I’m going to make this my MyChron loading screen.