Curious what everyone’s standard or goto upgrades from a stock OTK 401 is… I’ve found that allot of people buy different things but in the end only use 2 or 3 things…
Think for myself…
MXC+MXP rims
Extra axle (soft/hard)
Extra seat stay (+right side adjustable)
I have purchased but rarely used
Incline steering space
45/55 steering rod
Other kart brands I’ve purchased you basically had to buy camber/caster pills, front bar etc… OTK seems “complete” for the most part right out of the box.
I bought all the front bars. Adjustable stay for the right. 2 straights for the left. N, cut N, A, H axles. Long front hubs (we rain race a lot), neutral pills, mychron adapter, bumper savers, and I think that’s it.
There’s a TKart article about Callum Bradshaw’s World Championship winning kart. There really wasn’t much they did to it - threw some old radiator hose around the steering column to prevent damaging tierods in the pits, taped around the axle next to the hubs so they could see if it moved, saved some money on seat mounting by just using panhead screws and plain washers, and as a factory team they certainly had a full selection of wheels and axles.
How often do you switch out the bars and are there specific ones that are your go to? I find the most I do is adjust the standard 45 degrees sometimes.
Bumper savers and good skid plates for sure. MXC rims to go with the stock set. adjustable steering adapter. Then start collecting axles as you need them. We used N and harder, but YMMV.
The other suggestions here are good little pieces to have handy.
Personally, I consider the MXCs a must-have. Or a similar wheel. Something that will hold the tire in a more consistent temperature window. I’ve been running my MXJs for practice and even on a green track just running laps for practice, the drop-off in tire performance is noticeable after 5 laps or so. I can feel the right rear start to suffer pretty quickly. I may try some AMVs this year as well, as they seem to perform really well.
Different degree caster pills and neutral pills are also probably a must-have for me. Having the ability to fine tune the caster and go half-steps is really helpful.
The flat bar should get you through 90% of situations, but having a couple round bars as in-betweens is a good one. The flat bar is nice in it’s adjustability, but can be a little tough to consistently set it the same session to session if you’re changing it. The round bars are nice for that little added consistency.
Angled steering hub is a nice one to have too, so you can get a bit more push into the wheel, though some of that is a driver preference thing.
Same goes for the slotted steering shaft. Some drivers prefer the feel of less steering rate, but going up on the stock column is too much for them so some like the in-between settings on the slotted shaft. That’s pretty rare though I think. That’s all down to driver feel and if someone is being so picky on the steering rate feeling, I would just tell them to suck it up and drive it. 
The other things like bumper savers and skid plates should be added onto basically every kart brand. Those things are no-brainers.
In the end, you’re right, the kart is very complete from factory. The “upgrades” are more down to what level you’re racing at, as some of the finer adjustment pieces would really only be necessary if you’re experiencing big track evolution, going to different circuits, varying grip levels etc. like you’d see at a regional or national level race. Running locally or club level, you shouldn’t really “need” anything to make the kart better, unless it’s a part or piece that just comes down to driver preference.
Yeah I’m a lunatic so I have more stuff than I need. But yes MXC are great. I also run the AMV 9F and 3F. The only bar I use with lots of frequency is the chrome. I like it as it’s where I usually start the day. Then I’ll dial out some camber and ultimately go to the flat bar. But all heavily dependent on how much rubber the track is taking. Just use practice to try things. See what works and doesn’t. Even heat races if it’s still off to dial for the final.
Found it… good read!
Out of curiosity, why an adjustable seat stay for the right and not the left?
Also - are these adjustable stays from OTK interchangeable to each side?
@tjkoyen do neutral castor pills simply slow down the rate of adjustment, or do they narrow the operating range as well?
The neutral pills let you go halfway on caster. With the two eccentrics, you can only go full caster or neutral, there’s no in between. The neutral pill on bottom and eccentric on top let’s you do half caster so it allows for more fine tuning.
In a dry setting, how much caster/camber are you normally changing in the OTK? We run mostly at Badger and Road America, and have been running almost everything neutral.
My current setup at Badger is:
1390mm rear track
1 big spacer in front
1/2 positive caster
neutral camber
flat front bar
N axle
high rear ride height
neutral front ride height
1 seat strut per side
Tillett T11 VG seat set 10mm forward from OTK chart and halfway between the frame rails in height
18-19 psi on MG Reds
AMV 3F wheels
So basically I’m neutral/baseline except for rear ride height and a bit of caster.
I feel like I have a little understeer in the tight stuff I want to dial out yet and I’m slightly under-geared at 10/81 (I think?) but hitting just about 16k end of straight. I tried max caster last week but didn’t like it. Didn’t really fix the understeer and it made the kart bind on exit. I might just be slightly over-driving the entry to the hairpin which is where I feel it most. Still, that was good enough for a 49.2 on the National layout on a Friday. Could definitely be in the 48s on a Sunday. And with another tooth or two on gear I could probably find a couple more tenths. The straight is effectively shorter now with the repave since you have to brake slightly earlier for the Sweeper now, and 16k is too low for senior KA even before the repave, so I think a couple more teeth would let that thing scream a bit more.
I play with caster a fair bit but it really depends on the track conditions. Sometimes I’m neutral, sometimes I’m max. With my height typically I have SOME caster in the kart at all times.
We are neutral ride height in the back. Would high rear ride height be suggested for a 5’10 driver? 13yo.
We ran 10/79 last race and were hitting 15K regularity. Couldn’t get a good lap time due to constant battling for position.
The straight might be shorter, but there’s no lifting in turn 1 anymore. Maybe there wasn’t last year, and my driver just wasn’t capable then.
I would say your kid doesn’t need the raised rear ride height, he’s lanky. But if you feel like you need sidebite it will make a big difference on that. I can’t tell you what changes to make on your kart while it sits in the garage. 
Gotta see if there’s an issue before you start looking for a solution.
T1 is definitely faster now. It’s barely a lift in senior and definitely flat in junior. I drove a junior kart the other week and it was easy flat on a Friday even.
Wow, the track must be low grip. And thoughts on the wheels vs MXCs?
Also, try max caster with the bar vertical. I feel like it’s needed to balance out the extreme caster. You dial in some extra caster, but it doesn’t twist the front end the same since the bar is too soft.
It was just repaved so it’s pretty green. The grip level actually doesn’t feel awful, but the high pressure is needed to get temp in the tire. The 3F wheel actually feels good on the repave. I’ve done 20 laps stints with minimal drop off. On the old surface it ran a little too hot, and the 9F would’ve been better. The MXC is the perfect wheel for what I usually race, but the 3F works nicely for club or regional racing where there is less laps or less rubber. I would like to try the 9F at a high grip event.
I think the vertical bar with max caster is pretty extreme and far outside the window for a dry track. I would only try that in rain. I don’t want to set the inside rear down too early. The vertical bar makes the lift action way too quick in my experience. If you need front end and lift action, I prefer using one or the other, and caster does a better job of holding the inside rear wheel up. I could try a round bar, but still that’s a ton of front end to dial into the kart. The stiffer bar helps entry but hurts exit as it sets the inside rear down too quickly.
I run high rear ride height almost always, even in higher grip conditions. I only weigh 130, so it helps me get weight transfer.
I think a dot of positive camber, 5mm wider in front or 10mm narrower in rear would solve the issue. No need for a massive swing, my pace is just fine.
It’s definitely on the far end of tuning. The track was hot and slick. Added half caster and it went better. I went full max caster and didn’t like it. Since it was a practice day I said why not and stood the bar vertical and really liked it. Obviously, the front end was very responsive, but I could pitch the kart in quickly, get the rotation done pointed straight, and back on gas. All with very little steering input.
I think the front end being so stiff and needing very little steering input kept the kart from being bound up from excessive twist. I kept it that way for a practice day or two really helped me slow the hands.
Maybe it’s a strength or driver-size thing, but I don’t feel the half-step caster changes (concentric top or bottom) as much as I do a bar change. Your mileage may vary I don’t think my butt/hand sensors are as calibrated as yours. 
TJ, curious what your symptoms are with rear right height at neutral.
I tried a lot of different things yesterday and with the N axle/flat bar/half castor, the balance of the kart felt way off with an oversteer/sliding sensation late entry to apex. I imagine I’m a bit larger than you at 5’9" 180lbs, but raising the rear ride height was not one of the things I tried to get the balance of the kart where it needed to be. A stiffer axle was the solution that got the balance in the window for me.
Interesting, typically the stiffer axle will increase oversteer.
When I run rear ride height at neutral, the balance doesn’t really change, but the amount of sidebite does. With the rear ride height up, the kart just feels like it has so much more sidebite and actually feels like it’s transferring and working properly. With it neutral, usually it is very balanced and easy to drive, but just feels like it’s on top of the track rather than ‘in’ the track. Honestly when I raise the rear ride height it feels like I put softer tires on.
I only run neutral rear ride height when it’s really high grip, as then I don’t need the extra sidebite.
Thanks for the insight, definitely on my list to try now because your comment of it being “on top” of the track is maybe what I was trying to communicate with oversteer/sliding.
Agreed on the stiffer axle as well. I didn’t have a great reason to go stiffer other than I’ve had success on it before and had tried different bars/castor/ride heights on the front end and none of them helped the balance on the N.