Vortex super rok wont take rpm's in the bottom


I have bought a used Tony kart with a vortex super rok.

After my first session the other day, I noticed that the moment dont take rpm’s in the bottom end very nicely, only after some presure I can make the motor go spin up in the higher rpm’s. But it stops again at arround 14300rpms… And dosnt seem to go any higher. The motor should take 16k rpm’s
Any clue where to look ?
I have cleaned the caburator. But could anybody tell me the default position of the needle clip? Also the main jet is size 150, isnt that a little high ?
And what is the default for the mix screw ?

Any helt is appreciated.

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Jetting is a valid one, but the first things that come to mind are gearing and driving. If you happen to be a less experienced driver then it’s not unusual for your top RPM to be down due to lower exit speeds.

Also have you confirmed the gearing you should be running for that track?

I’m total new to the hobby. So maybe i need to give it more driver time ?
The gearing is 11T 79T…

This thread may help understand what James is talking about. Rok engines have better torque than say a Leopard/X30. Not knowing your engine, it may also have an electronic rev limiter that won’t go above say 15,000 rpm. Rotax limits their’s to around 12,500. Peak torque comes in lower around 9,000 rpm versus IAME which peaks around 12,500 rpm and has a max limit of 15,000/16,000.

The point is, depending on your engine characteristics, the track lay out (tight and twisty vs long and flowing) and driving experience, you may have to increase the rear sprocket to get the engine to rev to its potential. That being said, as a new driver, I would recommend gearing targets to just below peak torque range as you exit the corners. That way you get good acceleration until your driving improves and then you can go smaller again as you learn to take the turns faster and roll more speed to the exit. Its a balance and somewhat of a trade off. Better punch at low speed or higher top speed at the end of the straights.

If others at your track are running the same engine, you could ask them for a good starting point and then test up or down from there.

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Thanks guys… talked to a ROK GP guy. He adviced me to use a K33 needle, with clip in middle position (i’m on U2 needle now) and a Dp268 emulsiontube (using dp264 now) and a main jet arround size 142 for the spring weather we have now. How does this sound ? The motor is clearly running to rich at the moment. Looking forward to test

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