Modern Vespa

Hi,
I am doing a total resto on a '63 150GL and it has a stuck piston. The head was/is off and I have the engine off the body. The accumulation of dirt on the engine from 25 years of hard use was amazing!

Now to tackle removing the cylinder from the engine studs with a stuck piston is my next step.

What steps can I take to get the piston unstuck so I can pull the cylinder off? Soak the top of the piston in brake fluid and tap the piston with a piece of wood with a mallet?

I'd also like to upgrade the power as well since I sort of broke a fin off and heard the stock engine isn't too peppy.

Thanks All, Rod


It appears to be in neutral since the hub spins freely.

leave it stuck for now. chances are you will need a new crank so remove the studs and then split the cases.

You'll be left with a really nice bookend consisting of a cylinder, piston and crank but the rest of your engine will be usable.

That's what I did on my old Puch. It did the trick. Might have to worry about the crank and stuff, I don't know, but I was able to ride mine for years after this blunt procedure without replacing anything! I imagine it is related to how the engine became stuck - think the piston torqued and scoured the cylinder bad?

I heard the previous owner was out riding and the engine seized back in '88... so does that mean the crank is toast??

I once seized my kitted PX200 - the piston was welded to the barrel. I did a roadside repair - took the head off, broke the weld with a rock, and then rode home.

There was a small rough spot where the seize had occurred, but it was below the path of the rings, so a little bit of filing sorted it out and there was no loss of performance.

Hope you are as lucky. But try WD40 all over the rings first (you probably have already).

Mike

and in getting a top end for that GL, stay the hell away from other GL topends Put something ballsy on there. Throw a kit on the bitch!

Here are some pics...

No Bueno.

Would be a great time to strip that puppy down and start a resto project.

For sure a total restoration is going to happen. I will make a project thread.

Any other opinions on unsticking a piston?

How can you tell if a crank needs replacing?

now that you have the head off and assuming the piston is not at top dead center you should be able to rotate the flywheel and have cylinder move away from the cases if the crank is good. If it still won't turn then the main bearings or the bigend bearing is frozen, most likely from rust. Given the corrosion in the carb box I'd not be surprised.

Given you are in SF I can loan you my case splitter to make the job of getting things apart a bit easer.

A crank is ~$200 and well worth replacing if you're in there and as Eric mentioned the stock 2 port cylinder is no big loss. New crank and a 177 kit on the stock cases will give you the power of a p200 with no visible difference.

The piston could be at TDC.

Well I just started the soaking process and I'll wait a couple days.

Yeah it looks like a crank is like $180 and a 177 kit will be in the $250 range. What about carb upgrade?

Thanks Patrick for the tool loan! When I am at that stage I hit you up for it!

Pinasco has got a new 177 kit for 2 port cases:

"Pinasco is pleased to present the first cast iron cylinder kit 177cc specific for Vespa 2 transfers VNB, VBB, GL, GT, GTR, Sprint and TS made from 1960 to 1974.
The kit is projected on the base of the already tested cast iron 177cc for Vespa PX. The first and the second transfers are the same like on the version for PX, but the 3rd is closed and the flux of mix is regulated by the piston. The installation of the kit doesn't require any modification to the engine carter. There are five transfers on the cylinder, three more than on the original and the displacement is 177cc. The timing is studied to offer the best performance on the original engines and so the Pinasco 177cc is perfect to be used day by day in the traffic with low consumption, about 30km/l.
The Pinasco's kit 177cc for Vespa 2 transfers is the new that allows, who doesn't have a Vespa PX, to tune the vehicle without modifying the original carter and compromising the reliability of the engine.

The Pinasco's cast iron cylinder kit 177cc will be available from next November, the kit includes the head, piston, cylinder and all the accessories to install. Come to see it in our stand at EICMA Show in Milan Rho from 4 to 9 November, Hall 6 - Stand H35.
If you want to know more about it, please check the technical specifications on the webpage http://www.pinasco.com "

I notice that some manufacturers polish the piston and others like Pinasco, do not.

Does it make a difference? Could an unpolished piston create more drag?

Some piston makers like Wiseco actually makes pistons with horizontal ridges in them, the theory is that they hold the oil better.

Vertex pistons are coated with a teflon like finish..