Hi i have a problem with my 21 and i need some help with it...

In high rpm's (after 10k) and usually in 3-4-5-6 gears the bike seems to run out of mixture.With the choke on its a little better but still 5-6 gears do the same.After lots of tests it seizured but fortunately only a piston change...

It runs spliced, modded airbox and premix.The main jets are bigger than m-max suggestions.
I thought that maybe its the power jets but they were clean.

Now, i bough the hrc jet suggestions and i am ready to install them and test it.I will leave the power jets as they are just to be secured.

Could it be something else causing the problem or something i should do?
I dont want to seizure it again so any response would be great!