Rotax Evo top end issue

Hello all,

I purchased a used kart with a Rotax Evo junior gen 1 that was converted to a Sr max.
The top end seems slow considering I am using the same gear ratio as most other racers. The jet is a 122 and the max revs is high 11,000s low 12,000 which I think is kinda low from what I have been told (13,500-14,000) even the back half of the pack gain 30’-40 on a 250’ straight away. I removed the power valve, cleaned and oiled however still have the issue.

Would you think that it’s a PV issue? Or is there maybe some sort of restriction on a junior that was not converted?

Anything I can try?

Thank you in advance

Sounds like sprocket size to me. Try stepping up a couple of teeth - unless you know you’re on the same gear ratio as those pulling away (front and rear sprockets)