Modern Vespa

Just checking with others… Standard casings so no porting, 57mm maz crank, polini box.

Just did a WOT down a slight slope and hit 75mph @7400rpm on GPS (bearing in mind I'm 16 stone) is that about right ?

Also have bad vibration between 5300-6000 rpm, is that normal or potentially warped crank/flywheel/mountings ?

Speed sounds about right.
The vibration might be concerning.
Might be crank is slightly out of balance.
I would start by checking the flywheel runout, to see if the flywheel side is running true. I'm sure more knowledgeable members will chime in.
Cheers .

Speed and rpms are spot on. I ran two malossi 210 sports with P200E gearbox and the rpm drop is terrible after the shift from 3rd to 4th. You must have balls of steel to keep pushing it past 65 mph. You would have to tuck down to manage the cylinder kit to pick up more rpms and fight that wind resistance.

No that was me sitting fully upright and a bit of a wind wobble, I'll try the tuck next time so may get another couple or mph. I have a later PX with the cosa clutch so assume the ratio of different from the earlier p2's as gets up there pretty quick and no struggling between 3 to 4th.

To get there that easily and at about 7400... by any chance are you running a 22 tooth clutch and a 36 tooth 4th gear?

Nope, it's is just a standard 1997 PX200E engine. The polini box exhaust revs higher than my Sip2 though (that only reaches about 7000rpm)

Did you change the jetting between exhausts?

No but I did go up a bit before putting the Sip back on and left it the same for the polini. So running 140ac/BE1/130mj and a 50/140 pilot.

This a 24/24 carb? Drilled filter?

Yes Si24 and drilled filter

Yeah I just ordered a dial gauge to check as that is my suspicion. I may just chuck my original Piaggio crank back in as there was nothing wrong with it (although replaced it when I rebuilt in the winter just in case).

Will run smoother with a richer AC. I would re jet the whole thing with AC120/BE3 before changing the crank.

So the dial wheel came up very minimal readings of 0.05 variant (dial wheel setup on the crank edge with the flywheel off). However I did notice a gouge inside so not sure if that is current or a previous crank ?