Corsarino ZT

Singles built before the Lambertini era
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borispallanca
Posts: 2
Joined: 23 Apr 2021 13:59
Location: Bristol

Corsarino ZT

Post by borispallanca »

Help please. I have a 1969 Corsarino ZT 48cc. It starts Ok and seems to run fine for a short while, but then fades and cuts out. On examination, the spark plug is heavily coated with soot, dry soot and not oily. If I clean the spark plug, it will start again. According to the manual I am using the correct spark plug. I have tried fitting a hotter plug and this helps a bit. I have fitted a new coil, stator coil, condenser, points, HT lead, carburettor, all new parts from Morini Club Roma. It seems to be a running rich problem, but I do not know how to adjust the Dell' Orto SH/14/12/2 carb and turning the 2 adjustment screws doesn't seem to make a difference. I wonder if the main jet is too large, or if there is something else that I am missing. Any suggestions? Tony in Bristol.
mbmm350s
Posts: 666
Joined: 22 Jun 2018 10:18
Location: Reading UK
Location: Berkshire UK

Re: Corsarino ZT

Post by mbmm350s »

Hello Tony,

A fun bike for sure, and and interesting project.

One thing perhaps as you haven't mentioned it, have you checked the ignition timing, overly retarded perhaps?
I think the Dell'Orto tuning manual (you can buy one from Eurocarb) or find it on the web will cover the SH carb series.
And the new carburettor was configured for 4 stroke?

Mark
borispallanca
Posts: 2
Joined: 23 Apr 2021 13:59
Location: Bristol

Re: Corsarino ZT

Post by borispallanca »

Thanks for such a swift reply Mark, and useful comments. I think that the timing is right, at least it is set to the timing marks on the rotor and the crankcase. I assumed that the new carburettor would be already set up, as I bought it from the Italian Morini Club, and I have no idea how a carb might be set up differently for a 4 stroke (do you mean it might be set up for a different small engined motorcycle, a 2 stroke?) The new carb has the same number as the old one that I took off the Corsarino, SH14/12/2, but the old main jet is corroded and I cannot read the number that is stamped on it. I hadn't thought to remove the new carb and look at the main jet size, or what the number on it might realate to. During my on-line search for a solution, I came across an old posting to a motorcycle magazine from the owner a blue scrambler looking Corsarino, he seemed to have exactly the same problem as I do. The magazine suggested that he replace the condenser, but I have already done that. Tony
EVguru
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Joined: 01 Aug 2006 11:13
Location: Luton
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Re: Corsarino ZT

Post by EVguru »

The two screws are the slide stop and idle mixture. Off the top of my head, I can't remember if the idle screw is an air or fuel adjustment (turn opposite ways to achive the same mixture change).

If the idle stop isn't affecting the idle speed, they you may have the slide hanging on the throttle cable; Make sure you have slack.

Check the float setting, if the fuel level is high you'll be rich everywhere.

You may have a marginal ignition system as well as a mixture problem. The ignition winding, or coil may be giving a weak spark as they heat up.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
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