I have a ts50x(2 stroke) with a 70cc big bore kit and big one exhaust system . For jetting, it is running a 90 main jet as 67.5 is standard. When using about 2/3-7/8 throttle, everything seems to go smoothly and at 7/8 throttle it seems that would be full throttle if there was nothing else as it still revs out. When you pull the last 8th of the throttle at speed(pulling full throttle at a low speed/rpm won’t make it bog down, it will run as expected until it reaches a higher rpm) it seems to just loose power until I back off the throttle then the bike pulls again. I have done a plug chop (https://pasteboard.co/pIKgVUSpiVB6.jpg) after running flat out at the 7/8 throttle and it all looks good, a nice brown colour not showing that it’s lean or rich. I am really puzzled about this, can somebody give me some tips on how to fix this issue or help on diagnosing it, thanks. :)