Trouble Shooting help! By scottruel (Read 628 times)

[scottruel]

Hello, 

  Im new to Vespas, and im trying to help a friend fix his 1963 vespa. The vespa went "under the knife" originally because of a leaky carburetor. after much deliberation and trouble shooting, someone suggested that since the scooter was old, and the owner frequently left the gas (that looked as though it was quite old and dirty) on when not using the scooter, that there was potentially some dirt clogging some part of the carb, causing a back-up of fuel pressure which led to fuel spilling out of the top of the fuel bowl. I tried cleaning the carb, and drained the tank and put new fuel in, but the leak persisted.  I was able to find a new (reproduction) matching carb to out on the scooter and the leak was fixed. however, now the scooter will no longer start. When I first installed the new carb the scooter would start, idle high and rough, and then die. I figured maybe the idle was set wrong so I put the mix screw and the idle screw to the recommended factory settings and tried again, but still nothing. I can not for the life of me figure out what might be causing the issue. Spark plug is still sparking well, and is not fouled. Theres a brand new air cleaner on the carb. Im totally lost

My only thought is that the scooter had a Dellorto si 20/15 C, and the new one is a Dellorto si 20/15 D. Could this cause that big of an issue?  

Any help would be GREATLY appreciated

Thanks!

[cyborg]

Sounds as tho you flooded the thing when you had the original carb on it,,,pull the plug and change it with a new one,,,if doesn't start after that shoot a LITTLE starting fluid in the carb and kick it over ,,,it should pop,,,if it does you know you have a fuel delivery problem, drain and ,,pull the tank and inspect it for debris,,,pull the fuel valve and inspect it for dirt,,,it's probably packed with junk,,,,get some clear fuel lines so you can see what's going on,,,get a fuel filter in line

[gigster2000]

You might try a valv adjustment at .04 clearance if that doesnt work check your cylinder compression use a compression gauge being a 50cc you should be somewhere in the range of 140 p.s.i if not consider new piston rings.