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Author Topic: New Member - 1965 Spanish Motovespa 150s Second Series starting issues
Posts: 1
Post New Member - 1965 Spanish Motovespa 150s Second Series starting issues
on: July 16, 2018, 10:39

Hi Folks, thanks for the add, I'm having serious hair-tearing-out issues with a Spanish Vespa I've been given to get ready for the road here in Denmark, I've tried everything and just cannot get it to start properly, I've narrowed it down to the carburettor I think, but really need a second opinion (or 3rd, 4th, whatever)...before I tear the rest of my hair out. Here's what I've done so far.

Replace wiring loom and check/clean all connections. Replace points and condenser and set timing to 27 deg as required. Nice fat spark.
Casings split to repair badly welded crack on transfer port. Welded and cleaned up, tested with leak detecting fluid.
Cylinder and head air-tight; new base gasket and studs, head and cylinder lapped together with grinding paste, compression now excellent.

Float needle was worn, I'm waiting on a new one arriving but in the meantime I ground it down very carefully with a fine oilstone which showed an improvement.

I've fixed what I believed were the issues but still cannot get it to start, there's no problem with the fuel supply as the plug is getting wet.

It was flooding but I reckon this is the float needle. The atomizer tube (the part of it where the throttle needle slides in and out) looks a bit distorted but I can't find a new atomizer.

Could the starting isssues be caused by the atomizer, main jet, throttle needle, or pilot? As I said I'm waiting on a new float needle, the throttle needle doesn't look worn, I'e tried moving its position up and down but still nothing.

Pilot jet is the old one, but it's clean. Float does not appear to leak. Carb is a nice tight fit on the manifold, and as I said anywhere an air leak is likely has been dealt with (I think..)

Carburettor is Dellorto UA 19 S1.

Would really appreciate some input - I think the owner is losing patience with me, but it's really got me stumped; it's the first time I've rebuilt a scooter for someone else, I've been pad to get it roadworthy so quitting and handing it back unfinished is a no-no.

Obviously replacing the carburettor might cure it, but replacement UA carbs are mega expensive and a conversion kit to fit an SI not much cheaper, and as I don't own the bike it's not my call (a fair whack of money has been spent on it already so I'd rather not ring up again with another bill if I can find another solution first)........

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