My x7 kicks on about 70km/h and I had her geared even higher a one point and she could rev out on flat ground then aswell. Probably around 75-80km/h.
The mods are:
*Lightened flywheel. (I regret doing it btw.)
*Removed electric starter.
*Reeds. (Minarelli scooter engine reeds with harder fibreglass reed flaps & higher lift.)
*Ported exhaust.
*Added a boostport.
*Indexed piston.
*Hole in the piston skirt to match the boostport.
*Piston smoothened out under the wrist pin to help flow go up the transfers.
*A Minarelli scooter head (reprofiled to fit the x7 piston crown shape) and about 1mm squish gap.
*Matched transfers to case.
*Harder clutch spring & lightened clutch shoes.
*Geared up.
*Slightly advanced timing.
I know I could have done a far better job on the engine if I had the chance to do it all again from scratch. I think 80km/h or more (and still useable power) is quite easily possible (IF you have an engine from the correct factory, they differ alot and some cylinders, as an example, is utterly crap compared to other cylinders.) but you can never have a great acceleration on these engines unless you want to buy a new clutch every day.
You could however gear it down to about 50km/h and have a real nice kick in the acceleration. That's what I'm plannign on doing now. I want more acceleration.
Btw I just realised the x7 style carb has an air screw (Or is it another fuel supply screw?) on the top. I always thought it was for holding the throttle twister thingy in place but it's actually an air screw! I got the engine to run much better (cleaner anyway) simply by tweaking it around! Had to add a small o-ring though, otherwise the screw wouldn't stay in place since it didn't have a spring like mixture screws normally have.
