After a year of trying to get my cub to run properly,199cc Dellorto 22mm, (its always felt flat at the bottom and never felt like it would rev out),but after trying different carbs playing with and checking the PVL system i finaly got hold of an 'R' cam to try. On stripping the right side casing down to replace the cam i discoverd the problem, the cam timing was out by 3 teeth! the cam gear was lined up with a scratch mark and not the punch mark. I would presume that in this setting the valves were getting a bit close to the piston and this would explain the poor running(black plug,having to run strange carb settings to get it to run ok'ish) i am an average mechanic and since the engine was built in 2002 by Serco never suspected that it could be the timeing or that it could be set up that far out. Anyway anyone else had a similar experiance? At least its sorted now, the bike has what feels like 50% more power,picks up and revs out even to where i can roll the throttle off on a climb in 2nd and it will pull cleanly again.

YES and it happens more often than you think.................