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Vespa px 125 tuning
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Jlew2000
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Vespa px 125
Joined: UTC
Posts: 1
Location: Newport
 
Jlew2000
Lurker
Vespa px 125
Joined: UTC
Posts: 1
Location: Newport
UTC quote
Hi there, I have a 2000 Vespa px 125 with a 150cc top end and a sterling exhaust. I had a dellorto PHBH 28 on for a while but seemed too big so decided to put a PHBH 26 on instead. it runs and rides but doesn't seem to run as sweet as the 28 did. Any idea on what jets I require for either the 26 or 28?
Many thanks
Any advice much appreciated.
Jack
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scooterist
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Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
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Location: Tucson, AZ
 
scooterist
Molto Verboso
@scooterist avatar
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: UTC
Posts: 1624
Location: Tucson, AZ
UTC quote
You are running everything too big carburetor wise. You have more than plenty with a 20mm and it is probably responsive with a 20mm too. Do you still have the original
20mm carb del'orto or spaco? as per the jets, I honestly don't know on the PHB but on a regular 150cc engine and a exhaust you should be in the 108 -110 range. Stock 150cc comes somewhere between the 98-102 main jet.
Jack221
UTC
Jet Eye Master
PX221 MHR heavily tuned, PX200 O tuned, PX181 M1XL tuned, PX166 tuned a quite bit and some motorbikes
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Posts: 5305
Location: London UK
 
Jack221
Jet Eye Master
PX221 MHR heavily tuned, PX200 O tuned, PX181 M1XL tuned, PX166 tuned a quite bit and some motorbikes
Joined: UTC
Posts: 5305
Location: London UK
UTC quote
Jlew2000 wrote:
Hi there, I have a 2000 Vespa px 125 with a 150cc top end and a sterling exhaust. I had a dellorto PHBH 28 on for a while but seemed too big so decided to put a PHBH 26 on instead. it runs and rides but doesn't seem to run as sweet as the 28 did. Any idea on what jets I require for either the 26 or 28?
Many thanks
Any advice much appreciated.
Jack
What jets are in the 26 now?
ferriswolf
UTC
Molto Verboso
Joined: UTC
Posts: 1005
Location: Planet Earth
 
ferriswolf
Molto Verboso
Joined: UTC
Posts: 1005
Location: Planet Earth
UTC quote
Jlew2000 wrote:
Hi there, I have a 2000 Vespa px 125 with a 150cc top end and a sterling exhaust. I had a dellorto PHBH 28 on for a while but seemed too big so decided to put a PHBH 26 on instead. it runs and rides but doesn't seem to run as sweet as the 28 did. Any idea on what jets I require for either the 26 or 28?
Many thanks
Any advice much appreciated.
Jack
That carb is huge, do what the others suggested and stick the 20mm back on. That sterling exhaust is nothing but a noise maker too and wont benefit a standard 150 barrel. Stick a 20mm back on with a road 2.0 exhaust jetted four points up on main over standard. This is the standard jetting for a UK PX 150 recommended by allstyles in hampshire. So with a road 2.0, likely going up to a 120 main if using the combo listed below.

PX 150 (VLX1T)
CARBURETOR: DELLORTO SI 20/20 D
VENTURI SIZE: 20 mm
MAIN JET: 116
PILOT JET: 45/160
THROTTLE VALVE: 6823.01
MIXER TUBE: BE 3
AIR CORRECTION JET 150
STARTER JET: 60/100
@108 avatar
108
UTC
Ossessionato
V range 50s
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Posts: 2427
 
108
Ossessionato
@108 avatar
V range 50s
Joined: UTC
Posts: 2427
UTC quote
Jlew2000 wrote:
Hi there, I have a 2000 Vespa px 125 with a 150cc top end and a sterling exhaust. I had a dellorto PHBH 28 on for a while but seemed too big so decided to put a PHBH 26 on instead. it runs and rides but doesn't seem to run as sweet as the 28 did. Any idea on what jets I require for either the 26 or 28?
Many thanks
Any advice much appreciated.
Jack
Both the 26 and 28 should run great.

What's the current jetting?
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