Hi, interested in what you are saying about HRC cards etc but i do think a 9hp loss due to wear and tear is a bit excessive. My TZ250 even with worn rings only lost possibly 3bhp and that was pushing out approx 75bhp.

Surely your 25% loss must be due to other issues not just wear and tear.

With regard to Avgas i used to run it when i raced with Derby Pheonix and no one complained because i was never fighting for the lead. If it gives a reliable engine then go for it. Of course you could source the BP track day fuel at 102 octaine which is available at petrol stations near some race tracks!!!

http://www.bp.com/genericsection.do?categoryId=6621&contentId=7017179
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MC21 300
Aprilia RS250 track bike