While we all think a LS400 is the same as a LS650 with a different top end, none of us can be sure as we don't have one to compare.

Maybe someone in NZ has one.

I've done a search and it seams I was wrong, the 400 is 88 bore and 65 stroke.
Clive W

Someone in NZ does have one, well, i bought a 400 motor for spares for my 650. I can tell you it has the same cam, valves etc, head and bottom end and only difference is the bore size, BUT it does not have the decomp mechanisim on the head so fitting a 650 top end will be somewhat complicated re electrics and so on. Would be better off to hot up that motor with carb, exhaust, port mods and maybe even a new cam from Lancer, should be able to use all the same methods as for 650.
Without decomp mech will destroy starter and starter gears in short time methinks if you were to fit 650 top end without the additional wiring and solenoid for decompression.

chain conversion my nuts. You ought to be getting better than 90km/h. Thats about what...50-55mph? Whats your mileage (kilometerage(?))? Fuel consumption? Im going to take a blind stab and guess you've got something wonky with the carb and you're either getting too much or not enough fuel and thats holding back your top speed. Hows acceleration? Any serious lagging or surging when you twist the throttle? Clutch cable adjusted properly? A perpetually slipping clutch is no good for the clutch but would also limit top speed.

Agree with most here. 400 must do more than 90km/h stock. My 50cc moped was pushing 70km/h!

It may be power restricted for 16 year-olds (some countries had that too, a plate in the carburator which rectricts down to 12HP I think) or something is wrong.

Many thanks guys for youw help. You have right. there were two plates on input and output of the carb. many many thanks

rejet