Modern Vespa

Hi

I have the CVK Keihin carburetor on my Fly leader engine and I suspect problems with it no power after 30 mph and I disassembled it yesterday and the membrane has one or two holes and one of the screws of the tank is eaten so I can not check the jets. Would you have an idea of replacement for the carburetor or if someone has one not too expensive.

Thank you

Does something like that could work ? The 24 mm one. Actually I think I have the CVK 2600a so it's 26 mm.

You can buy the diaphragm and use small needlenose vice grips to grab and start the screw. Once you get it out, replace all the screws with allen screws. You will appreciate it next time you decide to get inside the carburetor.

Thanks but I can't find a diaphragm to be delivered in Switzerland better off buying a new carb all in one. I just got the choke to figured where is plug.

I was trying to find a re-build kit for a pre-leader ET4 and ScooterWest told me they are unavailable.
I don't know if it's the same for your model engine.

You didn't mention having looked at SIP. If you're in Europe and SIP can't help you…help may not be possible.

SIP-Scootershop.com specifically suggests the inexpensive Naraku carb that Mr. Nice showed for the ET4.

https://www.sip-scootershop.com/en/category/modern-vespa_3/tuning_1177/vespa-et4-125-150_T11/carburettor-manifold-reed-valve_2156/carburettor-carburettor-kits_3572?f-Artikeltyp=Carburettor&page=2

Thanks for the reply.

I find the part on ebay Deutschland for 20euros 14mm slide with the diaphragm.
But the naraku seems really good to me for the price. I wonder, seeing that he has a 105 vs 85 MJ for the Keihin if he could have a better top end. Because with the piaggio restricted air box it's lean from the start. I'm pretty sure it's better to give him more gas 😉

The Pre-leader ET4 was never sold in the United States, so it's highly unlikely that a US based dealer would have parts for it.
The OP's engine is not a pre-leader et4 engine either.

Try to install one and make the bike run right, then get back to us.

The Naraku is a typical Chinese GY6 carburetor with better QC. When we had the shop, we spent hours trying to get the Leader engine to run correctly with one, because it would save everyone a lot of money. There was always a dead spot in the acceleration. I know a guy who "successfully" installed one in an S150. I rode it. Big dead spot in the upper mid range. They don't come off the pilot jet and onto the main very well. It's likely a difference in the effusion tube and/or who knows what else. OTOH, I've spoken to people in Australia who claim they can get the Piaggio engine to work with the Chinese carbs.

Yeah the Keihin is a much more complex and better carb. If I can install this part and everything is golden and can get my power back I'm happy.

These Piaggio et al scooter Keihin cvk30 carbs are a cheap and nasty version of an OK carb that is used on Harleys etc

This version is seen on lawn mowers and other agriculture machinery.

No rebuildable accelerator pumps for instance, no rebuild kits per SE available but, some Harley parts transfer over, all be it not many.

I don't think their a use for a Cvk that big on Law and agricole machinery. Normally it's a slide carb that is used for 2T machinery not 4T scooters. And just for your information some Harleys use Keihin carb.

What is common with old Vespa carburetors and people who are "handy" with things, is that they will do one or more of the following, in no particular order:
get on the internet, get a lot of advice. Clean the carb a couple of times, send the carburetor out to be cleaned in some sort of machine, add some crap to the gas, replace the diaphragm. replace the electric choke, replace the jets, buy the $25 Amazon carburetor,

And then buy the correct carburetor for the scooter.

If there was a cheaper option out there, Scooterwest, ScooterWorks, and Scooterpartsco would all have them on our sites. That none of us do should tell you how well that $35 Vespa carburetor from Amazon will work out

I know Harleys use Keihin, the clue was in my post

Yes, some of the industrial bigger ride ons use Cvk, all be they smaller venturi, we are talking 4T