MOPED ARMY

those cylinders blow for low-end as it is, and they kinda suck for top end too, stock. The trick i've found (after modding at least 5 or 6 of these) a top-end pipe, somewhat agressive intake porting (piston skirt cutting) conservative exhaust porting, extreme head-decking, and really low gears. If you put a topend pipe on them they turn into the worlds nastiest hair dryer. I'm using a pockebike exhaust that doesnt even start to hit until 7k rpms, 14/16 gears, and i'm doing a really solid 40 right now, with tons of power from 23-35. the bike sounds like something directly from hell when it is on the pipe around 30 mph. Another thing that i've found really helps with wild exhaust ports is to use the front half of a pinto air filter as a 'velocity stack.' It will make your low to midrange much more tolerable, otherwise there is a big hole in the 18-23 mph area cause of the intake port.

I was hoping for someone to say something like "raise your and exauhst by 2.5 mm, and lower your intake by 3mm"

as far as what grahm said, I'v found that the chromed cylinder are the best cylinders for topend.

17:41 gearing, sava mc11, 50cc high compression head, top racing crank, 3 shoe clutch, malossi 15 intake, 16mm sha, techno hunter. new seals, gaskets, bearings, chain, and wheel bearing grease.

I think the problem is that the cylinder you are trying to port sucks. Ditch it. 11,22,or33=way more not shitty.

Or, cut the piston on the intake side by 1mm, raise the exhaust port by 1.5mm and widen both the exhaust and intake by 1.5mm on both sides.