Hi i have an aprilia af1rv6ap engine with a polini 70cc aluminium cylinder etc, standard exhaust, and igniton, 19mm carb with 74 main jet and 15,40 gearing, does anyone know why i can only get 65mph/ about 105kmph? Also it only revs to 9000rpm at this speed how can i make the bike rev more/go faster?

Thanks for any help and replies, also i have a spare cylinder which is malossi which i could port to make it go faster and to get use to porting if i decide to port the polini, any help on porting to get more revs and power would be appreciated.

Thanks again.

try another zaust

yes, the exhaust makes you go slow... buy a secondhand otherone or new, make sure the diameter of the front piece that goes into the cilinder is about 27mm up to 32mm.

you'll have to put in a larger main jet though

good luck

Thanks for the help, what about a bigger carb will this help me build up the revs and get more power?

np a bigger carb will only make you rev up to higher rpm. the power will be the same. I think a 19mm carb is fine but the exhaust is your main problem
if you want an other carb i suggest you go for a 21 or a 24 mm carb, higer would be okay too but it's not very economical (it uses even more fuel and delivers only a little more power)

Thanks again for the info, thought my carb and exhaust may limit the revs and speed, i will see about getting a different carb and exhaust .