Aggressive inside rear lift

Since moving to a 401 from my EVRR I’ve struggled to get the kart dialed in. The problem is on corner entry, it requires very little steering input for the inside rear to lift. It lifts very quickly and then drops which starts to cause it hopping which forces me to try drive around the issue.

  • at around 1min 40s I’m the kart in front - the problem is particularly noticeable on the left hander in this video.

same race from my camera if that helps.

I’ve tried a stiffer axle and removing castor - both didn’t resolve the problem. I have noticed that my T11VG seat appears to be a lot more flexible than others with newer seats - mines is very old now so perhaps a different construction or past it. Could this be the issue? I’ve tested another tony kart all be it a 401s and it was much calmer to drive - seat in the same position as mine. Other than the seat being sturdier everything was set the same.

The soft seat could definitely be a contributing factor.

My personal view just from that short clip is that if you drove any kart that sideways into a corner and had to put a handful of wheel in, it would respond the same. Have you tried not locking up so aggressively? The newer OTK karts have a ton of front grip and like you said, they will respond to every little breath on the wheel. They supposedly changed the chassis slightly in the switch from the EVRR to the 401.

Removing caster should help the issue typically, but if you have the wrong seat in, basically any change you make is going to be nullified. What front bar setting are you at?

Thanks for the feedback! With the EVRR I used to be a lot more aggressive but certainly have toned it back in the 401. I find the kart is very much on a knife edge with a very rigid front and soft rear if that makes sense. I can really feel the kart flexing. I tested the other Tony it was a lot easier to drive smoothly and felt a lot more balanced front to rear without one fighting the other. As I say only difference other than it being a 401s was the seat ridgity.
I’m running the standard flat bar horizontal.

I am in a similar boat with my kart. I have a older Tillett t11vg, has the seat be refiberglassed ever? I have noticed that since re-doing mine, the kart handles differently. The changes you are making will only band aid the issue. That seat is the problem. I had a really bad weekend at road America a few weeks ago. We changed everything and nothing worked. It only took us to the final on Sunday to figure out that it was the seat. In theory the soft seat should free the rear of the kart up and allow it to Flex more. The soft seat is a standard for the Rotax due to its low bottom end power. But if the kart is flexing too much, a stiffer seat should help(in theory)