1980 Vespa Grande won't idle/ hard to start

Christopher Ballard /

Just bought a semi running 1980 Vespa Grande Deluxe. It ran and idled when I picked it up but once I got it home its hard to start and won't hold an idle. Once you get below 5 mph it just does. Carb is clean and looks good, spark is fine and has a fresh tank of gas. Gas tank is fine- no rust or water. Any suggestions?

Re: 1980 Vespa Grande won't idle/ hard to start

stick a small wire thru idle hole below throttle slide, carb off.

Re: 1980 Vespa Grande won't idle/ hard to start

If the carb was clean then the bike would idle. Take it completely apart again and do what Pat suggests. I usually soak my carbs in Rubbing alcohol 91%, never had an idle issue after that.

Below is the money shot of what Pat is talking about

dellorto-1.jpg

Re: 1980 Vespa Grande won't idle/ hard to start

Hope necro'ing thread OK.

I'm having idle issues (could be from number of things I guess), but pulled off my new carb (I hardly ran it after putting on carb and exhaust last summer due to health problems) and can't find where the idle circuit comes out -- it's a dellorto 12.12 from moped division.

I checked according to Ninja's pic above, but there is no orifice there on this Dellorto. Any help would be great. Just trying to cover all the bases.

Re: 1980 Vespa Grande won't idle/ hard to start

Let us see a pic of your carb Eric.

Just like Ninja shows there has to be a idle passage.

Here I have one too

Re: 1980 Vespa Grande won't idle/ hard to start

I'll take a pic while I have the carb off tomorrow messing with different jets. I am guessing the idle orifice just in a different place on my new carb, be damned if I know!

Re: 1980 Vespa Grande won't idle/ hard to start

If you have the carb intake shim installed, it may obstruct your vision of the idle passage, but it’s there. Gotta be.

Re: 1980 Vespa Grande won't idle/ hard to start

There is a shim that females onto the intake, then males into the carb, as well as a rubber o ring. I had both of those pulled and set aside looking. I'll get a pic tomorrow, and triple check in the meantime (I ain't above missing the painfully obvious).

Re: 1980 Vespa Grande won't idle/ hard to start

Yeah I just missed it like a dumbass.

Poked it out with a stand from a wire brush, threw in a bigger jet, and copper hooped my exhaust junction. Ran and idled fine today after a little warmup and had a nice ride.

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