4th Gear Identification

I am building a Malossi 210 for a mate.

He decided to have the short 4th gear in (I didn’t do this when I did mine), so we ordered a T5 4th with the rest of the stuff.

When I went to fit it the T5 4th was too thin, which was when I realised (from checking previous messages on here) we had ordered the wrong one (should have been PX125 4th).

Anyway, just got hold of a PX125 4th, but…

The P200 4th has 35 teeth
The T5 4th has 36 teeth and simialar size teeth (seems a reasonable change)
The PX125 4th delived has 43 teeth and each of the teeth seem much smaller, is this the right one ? Is this going to work ?

That sounds very wrong to me. I dont have any reference here at the moment but from memory, the px125 has the same number of teeth as a t5. Does the gear fit onto the layshaft ok? It sounds more like a smallframe gear to me, again Ive no reference here so cant confirm no of teeth but its around the mid 40s teeth for a 4th gear s/f. Also, try the cruciform in the centre.

This is from the vespa tunning manual!
p200e 35 teeth
T5 36 teeth
early p125/150 45!
late px125 36
late px150 35
the nearsest to 43 teeth is second gear on the p200/T5/late 125/150?
does the layshaft that screws to the cruciform fit a 14mm spanner or 17,? as 14 is early gearbox and 17 later,also the later uses a circlip both ends. the early p2 uses the same number of teeth as the later p200 but with a better layshaft(grooves in the shaft to stop it jumping)
I think the first one that you got, might be right, as the T5 fourth(36) is thicker than the px125(36)

The gear fits on the layshaft OK.

I have also just realised that I have an old PX125 engine in the back of the garage (pre FL). Checked the gearbox in that one and the 4th Gear is the same as the one thats been delivered, 43 teeth !!!

I am now completely confused [:shock1:]