Modern Vespa

can anyone explain why the stroke of a px 125 and px 150 are different 58mm and 57mm respectively
I'm not an anorak I have just bought a barrel(in a box of ebay bits) it has three ports exactky like a px 125 but has a larger bore than a px 150 barrel (3rd oversize)I asume its been a 150 barrel bored out
i just wondered if I could i get a piston for it would it fit on my px 125 engine.then i couldnt get my head around why a px 150 and px125 could have different strokes when they have the same crank and con rod lenght which decides the stroke i believe.
I need to get out more

I think the best place for this is in the Not-So-Modern-Discussion section... RoverEric, Greasy, and others should be able to help you with this one...

Moved to the Not So Modern Forum.

Where did you find that?



It may be just a typo.



http://www.scooterhelp.com/scooters/VLX1T.px150e.html

http://www.scooterhelp.com/scooters/VNX2T.px125e.html



A mm is aprox .040 inch.....a very small increment.

Yeah, you should be able to use that barrel on your 125. They're the same cases and crank.

The stroke on almost all the largeframes is 57mm (PX80 and T5... excepted)

The older "150" bore was 57mm giving a displacement of 145.5cc

Later, not sure if it was with the P150X or with the PX150 they changed to a 58mm bore for a displacement of 150.6cc

Some one was just telling me not to believe everything i read on the net
cant remeber where i got htis info but here it is
Technical Specification - PX 125;
Engine - 2 stroke, single cylinder
Displacement - 123.4 cc
Bore - 52.5 mm
Stroke - 57 mm
Fuel - Unleaded petrol N.O.R. min. 95
Induction - Rotating valve in crankcase
Ignition - Electronic CDI
Starter - Electric and kick starter
Lubrication - Separate with automatic oil pump
Cooling - Forced air
Gear change - Manual, 4 speed
Clutch - Oil wet clutch
Frame - Pressed steel monocoque
Front suspension - Oscillating arm with helicoidal spring and hydraulic double effect single damper
Rear suspension - Engine works as oscillating arm, double effect damper
Front brake - Hydraulic with Ø 200 mm stainless steel disc
Rear brake - Ø 150 mm drum, mechanically commanded
Front wheel rim - Pressed steel rim 2.10 - 10"
Rear wheel rim - Pressed steel rim 2.10 - 10"
Front tyre - Tube type 3.50 - 10"
Rear tyre - Tube type 3.50 - 10"
Length - 1,810 mm
Width - 740 mm
Wheel base - 1,260 mm
Saddle height - 810 mm
Dry weight - 97 kg
Fuel tank capacity - 8 litres
Power - CV 9 (Kw 6.6) at 6,000 rpm
Maximum speed - 90 Km/hour
Lubricant Tank Capacity - 1,5 litres
Technical Specification - PX 150;
Engine - Single cylinder catalysed two stroke
Displacement - 151 cc
Bore - 57 mm
Stroke - 58 mm
Fuel - Unleaded petrol N.O.R. min. 95
Induction - Rotating valve in crakcase
Power - 8.2 CV
Start - Electric and kick starter
Lubrication - Automatic oil-fuel mixer
Cooling - Forced air
Gear change - Four speed, on handlebar
Frame - Pressed steel monocoque
Front suspension - Oscillating arm, coil spring and dual effect hydraulic shock absorber
Rear suspension - Hydraulic shock absorber, 88 mm stroke
Front brake - Ø 200 mm disc, calliper with two opposed pistons
Rear brake - Ø 150 mm drum
Wheel rims - In sheet metal, 2.10 - 10"
Tyres - Tube type 3.50" - 10"
Length - 1,810 mm
Width - 740 mm
Wheel base - 1,260 mm
Running weight - 116 kg
Fuel tank capacity - 8 litres (of which 1.6 litres reserve)
Emissions - Euro 1

It looks like the info has the bore and stroke of the px150 round the wrong way
i think this must be the explanation
Thank you confusion over