Modern Vespa

Hi Guys,

I almost feel rather sheepish asking this question but have exhausted what the problem might be. I have a number of vespas, all different models and currently working on a Sprint 150 engine and having put it all together when I kick the engine over the piston crank doesn't move up and down. It must be something to do with the clutch, even though I don't have the clutch cable attached (no tension) it just seems to be a soft kick on the kickstart even without the cylinder head on the barrel.

Please put me out of my misery by telling me the secret to what I've done wrong.

Have you put in the kickstart gear?? Did it catch under the spring leaf?? I'd take out the clutch and see if the primary (cush drive) turns when you kick it. If yes, there's something wrong with the cluth. If not, you'll have to split the engine again...

I can confirm I put the kickstart toothed gear back and the spring is pushing it against the Christmas tree gear stack, but what exactly is wrong with the clutch is my question?

No idea what is currently wrong with the clutch. IF there was any separation of the clutch plates the kickstart action wouldn't transmit any force to the piston.

I know some Cosa style clutches hit the oil channel in the clutch cover. If you remove just the clutch cover and try kicking it, do you magically have piston movement?

did you remember to put the woodruff key back in or perhaps it has sheared.

SaFis has the right idea...... Is it possible to have the kick start gear on backwards??
If the woodruf key was sheared, or fell out, it most likely would still move the crank and piston due to that it is a tapered shaft. may not run but i think it would move if the clutch nut was tight. scott

Not sure of the term your using "softkick" ???
if it feels like it wants to move or it is trying to move....check the keyways. scott

the kick start turns the layshaft, so right in the middle of things with clutch and crank on one side and the axle on the other.

put it in gear and press the kick starter slowly.
1. if the kick start lever moves but there is no movement of the rear wheel or the crank, then the issue is in the kick start mechanism.

2. If the rear wheel does move in the first test but the crank does not, then it has to be in the cushgear or clutch (more likely clutch).

Hello. May I suggest you loosen the clutch cover so it's slack and try kicking it over. Something could be compressing the clutch internally.

just throwing this out there . . .
did you forget the gudgeon / wrist pin?

It's only the smallframe that has the clutch mounted on a taper and it has a rather small woodruff key as the tight taper does most of the work. This one is on a straight shaft, at the end of the crank, and a huge woodruff key to handle the additional load.


If the motor is still out of the bike, pull the clutch cover & watch to see what spins.
If not, put it in gear, rear wheel off the ground, spark plug out and you spin the fan wheel, what does the back wheel do?

What happens when you put it in gear & roll it?

Sorry for the late reply here on what was actually the problem that I resolved shortly after posting. It had to do with the LML Cush gear / Christmas tree gear which interlocks with the clutch being slightly different to that of a VESPA Cush gear and I had mixed these up when re-assembling the motor. Runs like a dream now