Vespa 1963 Sportique convert to 125cc

[martchin]

Hi All I'm new to this scooter game so please correct me if I'm wrong about anything. I have a 1963 Douglas Vespa Sportique 150cc that I am restoring. As far as I can tell it's pretty much a Piaggio VBB except put together in Bristol by Douglas. I want to reduce the engine size to a 125cc so it can be ridden on a CBT. I believe the VNB was a 125cc model using the same basic engine. My questions are how easy is it to convert? (New cylinder, barrel and head? Timing adjustment?). Obviously dependant on the answers, any ideas where I can get the cylinder kit from (2 port I think). I've looked on beedspeed and unless im missing it they don't have one. Any help would be much appreciated. Thanks in advance.

[henri]

its a straight swap ,barrel/head/piston , you need to check the little end bearing first tho , as douglas built sportiques used the older style solid bush bearing , douglas assembled italian vbb's used a later 16mm roller bearing little end . as a guide if cases have douglas cast into them it might be the solid type , if piaggio's cast into them more probable to be roller,
if its a roller type the barrel kits for 2 ports are easily available in this country or cheaper from india via e bay , also the later 3 port px barrels will fit but you wont get any use from the 3rd rear port .
if its a solid bush small end your best line of enquiry is probably bill drake from the vespa club of britain , tho memorys telling me on my douglas sportique 150cc the pin from a roller small end n piston fitted the solid bush conrod nicely .but havent done many miles on that engine yet so cant say its a definite fix yet , H

[bryno]

Have a think about how you will register it as a 125, if the scooter is currently not registered, when you get the dating certificate done they will put it down as a 150 on the docs as that is the engine code says. If you do need a dating certificate I'd call Bill Drake at VVC first and ask him how you can have it dated as a 125 on the cert.

If you have a V5 already, you'll need to get proof that you have converted it to a 125, that usually means getting a garage to do the work for you and then issue a reciept for the conversion work. It will be a bit harder to get someone to provide this paperwork if you do the job yourself.

Alternative is to get an official scooter club to provide paperwork to verify the conversion, that is not guaranteed to get through DVLA but worth a try.

Worth just working this through before you decide about the parts..

[martchin]

Thanks guys really appreciate the input. The little end is the needle bearings so I'll make sure i get the same. I'll also email Bill Drake before I order anything.

[henri]

as bryno says , dvla are supposed to accept a receipt for a 125 barrel an a declaration from the mechanic/shop that did the work as proof ,but can get funny about it , if its not registered yet be sure an state to whichever club you get to date it its a 125 an send receipt for barrel with the other proofs they require ,an when filling form for dvla dont mention 150cc at all. they can get funny n nit-pick given a chance .
as its a needle roller little end any of the 2 port barrels on the market will fit ,most are 150cc ,to get a 125 one you might have to fit a 3 port px type 125cc barrel, H

[martchin]

Thanks Henri do the PX pistons have the deflector on top?

[bryno]

No, but you can fit a matching head for a domed top piston, the deflector type set up is different, domed headed Pistons work better anyway whcih is why they junked the deflector set up.

I've never tried a 3 port barrel on a 2 port engine personally, but in theory it will work, just not as well as if the casings were also 3 port to match.

[henri]

definetly junk the deflecter piston n head ,its a really flat engine tune ,the dome type are better an lots easier to get ,H

[martchin]

Again thanks both of you

[martchin]

Another question I have is how easy is it to blank one of the three transfer ports if I get the px barrel. Can't seem to find anything on the Internet. Thanks

[bryno]

You don't need to blank it, it will just sit on the casing with no matching opening so it won't operate.

[martchin]

That explains why I can't find anything on the Internet. I thought that would screw up the compression but that makes sense now as the port would be closed by the piston during most of the compression.

[henri]

tho px barrels do have a locating dowel in them that fits into a hole on exhaust/front side of cases , if barrel turns up with a dowel an youve no hole twist the dowel out with molegrips n discard . H