I don’t know if you can help I have a Scorpa SY175 which I bought new here in New Zealand a year ago,which is a French built trials bike with a Yamaha TTR 125 bored to 143cc which is a Powroll engine which the French buy in and fit to call it a SY175 model! http://www.scorpaaustralia.com.au/bikesSY175F.html I have played around with the carburettor changed pilot from 15 stock to 17.5, and main jet tried the 102.5 but it runs better with the 105 stock jet since I have lightened the flywheel by 1.65kg. The problem is it still won’t rev out when you turn the throttle fully, and if you just wind it out will tend to stall. The air filter is soaked in Bel Ray foam filter oil. Do I need to go larger on the main jet to experiment?