HM Derapage CRM 125 2T not getting to the power band
As the title says, the bike isn't getting to the power band. Year 2014, so it's a Rotax 122 engine.
When we bought the bike a few weeks ago, it ran well and had lots of power and it went to the power band easily.
Now it doesn't matter how long you hold the throttle wide open, it just won't get to the power band.
Everything is stock except Scalvini performance header and Dellorto VHSB 34 carburetor.
Edit: Forgot to mention. Bottom end serviced and balanced, top end replaced a couple hundred of kms ago.
Rave power valve has been adjusted to the weakest preload in order to eliminate the power valve for diagnostic purposes.
Carb settings upon purchase were stock K57 needle, clip in the highest groove, 160 main jet, 266 needle jet.
We have:
Checked the reeds
Clean and oiled the air filter (with proper air filter oil)
Fixed air leaks in the carburetor boot (and verified the fix with carb cleaner while the engine is running)
Fixed an air leak in the exhaust header in the cylinder side
Serviced the power valve to make sure it is not stuck
Checked the compression
Replaced the spark plug and gapped it correctly
Tried multiple main jets between 150 and 170 (we are now at 170)
Tried K21 needle for a leaner midrange
Current jetting:
K57 needle, clip in the highest groove position
170 main jet
Everything else is stock
Currently we believe this is due to jetting but we are not able to diagnose this fresher.
All advice and diagnostic procedures to identify the reason and fix it are appreciated.