Modern Vespa

So I recently got an old 50s from a lady that drove it back in the early 70s. the cylinder and piston where shot so I bought all new cylinder kit and crank from SIP. When I went to install the cranshaft it was hitting the lip of the rotary pad. So then I made a post on a vespa facebook forum with added pics of my situation asking for help, most people sugested grinding down the area it was hitting and rubbing with a dremmel. And so I did, I removed a good bit of the pad not knowing that it had a crutial function to the operation of the engie.

I eventualy found out that if the pad had even a little groove it would be shot.

Now the engine sits assembled and I am wondering if it even has a chance of giving any signs of life. Additionaly I am wondering how the caoil is suposed to be wired up; since most diagrams I have seen do not help as much, and I see that there is more than one wire that gives a spark.


img shows the new mazzuccelli crank hitting the lip of the pad
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This is your big chance to convert to a reed intake.

You might contemplate upping the displacement to a 125/135cc top end while you're at it.

yeah thats too bad: because I already bought an 85 kit and Im not the biggest fan on buying a new one.

I am new to vespa engines anD ive never seen a rotary pad nor do I know how it works.

can you share a link to the crank you installed? It shouldn't be rubbing, but I'm curious what's going on because either the crank is wrong or the cases are toast.

Did you replace anything besides the crank?

this is the crank: https://www.sip-scootershop.com/en/product/racing-crankshaft-mazzucchelli-for-vespa-50-n-l-r-s-special-sr-ss-pk50-s_45061500

and this is the cylinder: https://www.sip-scootershop.com/en/product/racing-cylinder-polini-85-cc-1400059-for-vespa-50-pk50-s-xl-xl2_14000590

and no, business as usal besides that you know, new bearing new gaskets

That crank doesn't look like it was pulled in correctly. I never encountered a crank that hit the pad. Since the pad is now damaged, reed inlet manifold, reed cylinder or new cases…

welp, with some cold and heat and a few lovetaps it went in allright. and on the alternator side it spun like a dream

This is the manifold you need if you're keeping the stock carburetor…

https://www.sip-scootershop.com/en/product/intake-manifold-polini-for-vespa-pk50-125-s_21502030

https://www.sip-scootershop.com/en/product/intake-manifold-polini-for-vespa-50-125-pv-et3_21501160?usrc=Intake%20manifold%20Polini

Get some measurements but this might work with the stock carb and solve the rotary problem.

Might be the camera angle but it does look a little cockeyed.

No "tapping" a crankshaft, even lovingly. You pull it in instead.

This^.

Also, how much of the pad did you grind off? It may be ok. There are plenty of vespas riding around with imperfect pads. Some pictures would help.

It's essential not to bang on the crank though. It gets pulled in. You can "tap" it out because you won't be causing it to distort. Pushing it out is the preferred method though.

welp its pretty fucked, the whole top part and tapering down twords the middle is gone.
But im mostly having troble understanding what this pad does, ive never met anything like it before.

I have two videos for you. One describes how the rotary intake works.
The other shows what you'll need to do to convert to reed intake if the pad is F'd, using the Polini manifold linked to earlier.

And true the crank. You can search the subject here.

&t=70s

It's simple. In order for the rotary valve to seal properly, the gap between the crank and the valve inlet cannot exceed 0.05mm, in position when the crank web is closing the inlet. The pad is there to ensure this.

You don't necessarily need it, as long as the gap is less than 0.05mm.

I have used Luca at Moto Web in Misterbianco, Sicily to fix a rotary pad before incase you need a "hail mary".

https://share.google/Ub358SRKXT9togmVz

He charged I think 130 Euro a couple years ago to weld up and cut a new one. I asked him if i could mail cases to him in the future and he said that would be fine.

I think you should split the cases and figure out why the crank is hitting the rotary pad. From the photos, it looks misaligned. First step is finding out why. Next is checking the condition of the rotary pad. It might not be too bad. Would be good if you could get some hands on help.

No shame in asking for help or making mistakes. We have all made them.

[quote="Ray8"]
I have two videos for you. One describes how the rotary intake works.
The other shows what you'll need to do to convert to reed intake if the pad is F'd, using the Polini manifold linked to earlier.

And true the crank.

Well I see the guy thats deleting the valve is also making a litlle port on the side, will I have to do this? I'm really scared of fucking this up more.

Also will the crank still work? or will I need a full circle one?

Many new things for me here, thanks in advance.

No. That's him port matching a new kit. I think he says to ignore that. Mine has a rotary crank. Works very well with the Polini reed manifold.

Can you post a pic of your pad?

Mine has a rotary crank. Works very well with the Polini reed manifold.

Can you post a pic of your pad?
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Well I guess its good that I wont have to get a new crank.

But the engine is assembled, and I wil be checking if my alternator and Ignition is good. So it will take me a few days or even a week to get to that point considering I'm working late these coming days.
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