OP
@psgnw avatar
UTC

Hooked
Vespa PX125 Lusso - Honda CB400N - Yamaha SR400
Joined: UTC
Posts: 128
Location: Norway
 
Hooked
@psgnw avatar
Vespa PX125 Lusso - Honda CB400N - Yamaha SR400
Joined: UTC
Posts: 128
Location: Norway
UTC quote
I have a 75cc polini mounted on my smallframe (PK 50 XL2). Been riding it for a season or two with the standard 16/15 carb. I have a 19/19 carb + manifold laying around. Is it worth the hassle to mount the 19/19 carb? What would be improved with a bigger carb? More torque, cooler engine or just more wasted fuel?

The scooter is fine for town and small road use, but it could do with more power when going up hill.

I have a standard unrestricted exhaust mounted.
UTC

Addicted
Joined: UTC
Posts: 954
Location: Planet Earth
 
Addicted
Joined: UTC
Posts: 954
Location: Planet Earth
UTC quote
https://www.sip-scootershop.com/en/product/racing-exhaust-sip-road-banana_24176000?cr=3a6304bb-cc81-4ed5-9f63-1ff45fe1abfa&gpc_origin=shopping&gpc_feed_alias=de&gpc_pid=24176000&gclid=CjwKCAjwg4-EBhBwEiwAzYAlshWi1ggPZNu17cV3fMf1OcNvM54WIlMDJMeCNaT8Qdfdz1Lv9G-cZhoCchUQAvD_BwE

Stick one of these on. They are very good I'm told. I'm sure the small frame gurus will chip in soon. I'd start with one of these and upset carb by few pts. Exhauts are everything for a bit more grunt. I think the 19mm carb is a must for the 135 kit so probably not worth it to you and all the headache of setting up. You know your existing carb is set up right and all you will do is increase main jet size. At end of day you have 75cc but I know these banana pipes are very popular for the torque. I had a genuine piaggio banana pipe on a pk years ago and it was a lot more peppy than standard.
OP
@psgnw avatar
UTC

Hooked
Vespa PX125 Lusso - Honda CB400N - Yamaha SR400
Joined: UTC
Posts: 128
Location: Norway
 
Hooked
@psgnw avatar
Vespa PX125 Lusso - Honda CB400N - Yamaha SR400
Joined: UTC
Posts: 128
Location: Norway
UTC quote
Sure I could put a "performance pipe" on it, but the carb I already have I don't care about more speed (I have my PX with 177 on it for that). I just wonder if it's worth slapping the carb on it for more grunt.
@moto64 avatar
UTC

Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1884
Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1884
Location: S.Salem, NY
UTC quote
The 90's came with 16's and didn't go they didn't up to 19's until the 125. It's all about the air flow volume and speed through the venturi and a larger cab probably won't meter the fuel properly with the smaller cc volume.
On big American V8's they run with multiple carbs or multi-barrel carbs because the smaller venturis metered better than one big venturi in a single carb.
A pipe will surely make a difference and some are better for low end and others are better for speed. Jetted right, the 16 will most likely be fine.
OP
@psgnw avatar
UTC

Hooked
Vespa PX125 Lusso - Honda CB400N - Yamaha SR400
Joined: UTC
Posts: 128
Location: Norway
 
Hooked
@psgnw avatar
Vespa PX125 Lusso - Honda CB400N - Yamaha SR400
Joined: UTC
Posts: 128
Location: Norway
UTC quote
Thanks for the replies. There is so many opinions about this floating around. Some say that a 19.19 will wake up the polini, and some say it would run best with the 16.15 carb.

Have anybody any experience putting a 19 carb on a 75cc?

I have the carb, but it's not tempting to mount it and redo the jetting (which is so cumbersome on a smallframe) if there would be less benefits than trouble
UTC

Addicted
Joined: UTC
Posts: 954
Location: Planet Earth
 
Addicted
Joined: UTC
Posts: 954
Location: Planet Earth
UTC quote
On the sip website for the polini 75 it states this SIP-TIP: Adjusting main jet and a new spark plug is a must. Transmission recommended here is at least the PINASCO pinion or a 3.72 transmission. The engine is made even sportier by a 16/ 16 carburetter, original exhaust with wider manifold, SITO Banana or POLINI racing exhaust.
DoubleGood Design banner

Modern Vespa is the premier site for modern Vespa and Piaggio scooters. Vespa GTS300, GTS250, GTV, GT200, LX150, LXS, ET4, ET2, MP3, Fuoco, Elettrica and more.

Buy Me A Coffee
 

Shop on Amazon with Modern Vespa

Modern Vespa is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com


All Content Copyright 2005-2024 by Modern Vespa.
All Rights Reserved.


[ Time: 0.0192s ][ Queries: 3 (0.0072s) ][ live ][ 313 ][ ThingOne ]