How to reduce CC

[shaun]

I've a 1978 Vespa PX150E but says on log book it's a Vespa Douglas and was wondering if anyone knows how I can reduce it from a 150cc to a 125cc without changing the engine? Want it done aboveboard cos will then need to send log book to DVLA to change cc. Thanks.

[andyboi]

Change of engine number or cylinder capacity (cc)

You need to provide either:

a receipt for the replacement engine
written evidence from the manufacturer
an inspection report provided for insurance purposes
written confirmation on headed paper from a garage (if the change took place before you bought the vehicle)

Gov.UK website

[henri]

to reduce the cc its a swap 150 barrel/head/piston for a 125cc one . an re-jet to suit . to change logbook its receipt for 125 barrel an note from mechanic/shop who did the work . H

[ianmartin40]

I did not think anyone actually did this and they just got paperwork from someone they knew, friendly mechanic etc, there are loads of px 125`s with 180 kits fitted and not declared, I`m not saying it is right but it is common, and what is the HP difference between a px 150 and a 125 anyway?
even a px200 is less than 12hp!
This is just DVLA and insurance companies making you jump through hoops to make you fit their criteria..... all of a sudden the home mechanic is no longer competent to fit an new piston, barrel and head and you need paperwork etc etc yet this is a job you can do yourself, the big bore kit makers supply all you need and if you buy from a reputable dealer they will also supply the carb jets needed to go with the kit if you tell them what you have and what you want.
Rant over!!!!

[andyboi]

VED doubles from £17 to a whopping £39 over 150c.c. surely,surely you don't want the government(agency) to miss out on its £22 p.a. fee ?