Converting OTK (redspeed) to 4 stroke. What axle, and what else is needed

I picked up a redspeed roller that I am going to run in lo206 heavy (390-410 depending on track)

It currently has the stock medium axle that i will drill for inboard sprocket.

I am wondering what other axle to get. On my old kart i switched to a soft and it helped a lot, but not sure if OTK respond the same.

Also, are mini gears required? The other chassis i have messed with were 4 stroke specific.

OTK is opposite. You will likely need to go harder on axle as the summer grips up. Keep your eyes out for an H or HH.

@KartwerksDan can tell you anything else needed on getting started with an OTK in 206.

1 Like

I’m not sure where you’re located, but some things I would look at:

  • Hard or double hard axle like derek said. You may also want to cut this down to 1000mm
  • I’ve seen some run additional seat stays to really stiffen the back. Like Derek said, OTK gets freer or looser with a stiffer rear end
  • Rims. The standard spoked ones might provide a little too much grip, you might want to look at MXC or similar (douglas, swift, AMV has good options @Paul_Montopoli )
  • Someone else can weigh in, but you may also want to look at different caster pills to take a bit of the caster out of the kart. 206 has such little power that everything you’re doing to the kart is aimed toward getting it to drive off the corner well and not bound up

thanks, that helps a lot. It was used in KA, so it already has seat stays. I was going to put the sniper conversion on the front to make adjustment easier. Ill probally get it driving then see how it handles and figure out where to go from there. Im racing out of oklahoma city

We ran OTK 4 stroke a couple seasons before going KA.

No special gear to go from 2 to 4 stroke besides the inboard keyed axle, motor mounts, and twist or split sprockets. We ran MXC in KA and 206, I consider those a must in any warm weather racing in either category.

For 206 we found the kart worked well in cold or wet with the stock N, occasionally we went softer but not usually. Full narrow N and ride height was usually enough with my very tall driver.

For summer though, it could get tough. Strongly recommend having an H and even HH on hand if you have tracks that pick up rubber and really grip up. If that isn’t enough to keep the rear from binding up in the summer, then start cutting axles down.

We typically ran with NO struts almost 100% of the time in 206. KA we usually run 1 strut per side. Again, very tall driver though. 76 inches / 193.5 cm.

EDIT:
@nBrewer just recognized your name. You are a new NTK racer aren’t you? I can’t speak for the new asphalt there, but I can speak for our weather. You will definitely want to experiment with a cut down axle in the summer heat there, especially if there is a decent field of karts. The old asphalt and coatings could make the track a bit extreme from cold to hot, I hope the new surface makes it behave more like other local tracks now!

Lots of good information above there.

For axle we tend to like H for Medium, HD/HH for Heavy/Masters.

We typically run full strut package with the Mojo or MG up here but did have some luck with no struts on the Vega. We also found seat position 20mm further forward had some benefit when the Vega grip got crazy.

Standard hub and gears works fine but the Rocket Mini is nice to work with for sure. Just a preference question for you depending on what kind of gears you have on hand already.

We run a very conventional KA setup on the 206 OTKs actually. With the harder axle too we tend to treat the front very similar - half caster and round bar for most of my heavy/masters drivers.

In our playing around and testing we’ve found the 206 OTK karts to be faster just treating them like a conventional OTK here. But your track/tire combo may vary!!

1 Like

I hope to run down at NTK this year. We currently run up in tulsa. im 6’, 225 lbs so im betting a hard axle will be the ticket.

Depends on your tires and grip level, but for a 206, you’d likely want to free it up, and it sounds like that is what helped with the other kart. Consider the hard axle as others have said (it is opposite), and try without the extra seat struts. Wheels out to the max (55 1/8").
Note that some aftermarket axles (Swift) have both inner and outer keys).

Here are pics of mocking up the motor and chain.

I just want to see if it’s normal to have the motor so far to the right.

If I ran mini gears and a 0 degree mount I could maybe move it to the left a bit.

Currently the seat looks pretty centered. Should I try to offset it more?

Both my old margay, and our crg fs4 were built for 4 stoke, so I not used to everything being so close.




If there is any room move it to the left 1 hole. It is hard to judge in the picture. Usually the Li opting factor is the seat strut. At least for me. Other than that you are set.

We bent the left side seat strut out, then put spacers on right to shift seat over more.

We also ran with no extra stays/struts 99% of the time.

@nBrewer, fix your post on FB. Comments are off right now. Won’t get many answers that way! :rofl:

Sofar here is what i have done, and its getting close.

I bent out the left strut. I am going to need to go up to a XL seat to fit with my rib protector.

I reversed the clutch and moved the motor in lot.

I think i need to move the motor furth back. How far are you guys setting your motor back?

You can go back a few inches at minimum, if you need.. I like mine in front of the cross member so that the mount doesn’t sit on that weld, but even than some folks go back that far.

fixed, thanks for the heads up

Thanks for the call out David. I always recommend for 3F or 9F for 206 karts. Can’t go wrong with either.

Where Nik is going to run he will definitely want to pursue a set of MXCs or 9Fs. Summer temps and grip levels both get crazy for us.

Our grip level up in tulsa is not near as high as NTK. Does NTK get less grip in the fall / winter?

With the old surface, dramatically less. With the new surface I do not know since we mostly regional race now. I expect it should be far less dramatic change with temp than the rhino lined track surface was.

Also, find a small piece of Kydex, heat form around that crossrail, and adhere with some 3M VHB tape…will save chain rash.