Modern Vespa

Evening all,
I have been slowly getting round to working on my gtr 125 and discovered that the clutch exploded which is why the think wouldn't turn. anyway, I need a new clutch, but the crank looks like it wouldn't hurt being replaced

given that I will replace both these parts, would anyone have any advice on what I could replace them with? I still want to be 125, but if there is something that will run better or anything i would be happy to hear.

also, as I'm at it would you recomend a 12v upgrade with electronic ignition? or anything else worth considering at this stage?

many thanks
chief

I would go with the elec ignition. I have a 73 GTR but it is still on points and 6V. Am I right in thinking you need to change the crank to a different taper to go up to 12V. This is the reason I have not done it yet. Also a 6V wiring harness is not suitable and will require some changes.

On seeing the picture. There is pretty much no doubt.

https://www.sip-scootershop.com/en/product/clutch-sip-cosa-2-race-ultrastrong-22-teeth-primary-64-65-67-68-teeth_93404300?cr=3a6304bb-cc81-4ed5-9f63-1ff45fe1abfa&gad=1

Buy this. Forget about clutch issues, forever.

This version will fit on a pre-1975 GTR taper:

https://www.sip-scootershop.com/en/product/ignition-sip-performance-by-vape-12v-ac-road_510061RA?q=vape

it's still a 125, surely a stock 7 spring clutch (not even a banded one) would do the job?

If your ignition has no issues, why replace?

Go with a stock clutch and crankshaft; it's all you need.

I would of course update your seals, cruciform, and at least your crankshaft bearings.

Thanks for the tips.

I'm going to be riding dry weather only and in the summer.

thought I would check in to see if there is something I can change up while I'm at it. any better equivalent to a stock crank?

Can we see your original crank, pics of where it concerns you?


I don't have a lot to add except that I think that original Piaggio factory stock parts are usually quite good. I've built a few mildly tuned motors and always used stock cranks, never had a problem so far. I think on the other hand that some of the cheaper replacement cranks are worse than stock including name brands from things others have reported.

If you DO want to upgrade, I suggest you contact member SaFiS who I believe is up on the current state of modern crank affairs.

If you don't ride at night & don't need 12V lights, stick w/ your points. And a quality stock clutch or even a 7 spring is all you need. There are a LOT of advantages to sticking to essentially stock if your bike was running well before the clutch let go. You may be better off putting your money into a modern box exhaust and upjetting to match if you wouldn't mind a modest power boost.

Hello again,

I have no idea how the bike was running before as I bought it as a project.

You saw the pic of the clutch. no idea how that happened, happy to replace with stock. As for the crank, the woodruff slot is a bit flared, bearings just slip on and off one side and there is a slight wobble to it so difficult to see in a picture.

I read somewhere that on the stator plate you can replace a coil to get 12 v lights. anyone know anything about that?

The stock clutch type you have is awful. Old and out dated, stiff to pull, draggy, and prone to doing what happend to the last one. If you like originality, keep it but better functiallity and reliability are readily available.

There are many better cranks and 12v electric conversions available, if you wish to go that way. One with a 60mm stroke and PX taper, to use PX electrics and flywheel would be my choice.

thanks, any specific recommendations for the clutch? or cranks?