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New Member - 1965 Spanish Motovespa 150s Second Series starting issues

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ross80 Ross Jenkins
Grevinge, Denmark, Denmark   DNK
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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OlympiaScooterCompany Silver Member Matthew Gatlin
Olympia, WA, USA   USA
Did you replace the seals when you split the case? Also have you gone through all the jets with a paperclip to make sure they are not plugged?

Matthew Gatlin
Olympia Scooter Company
Cell: 503.954.4043

amstrum Mark Strumolo
Naugatuck, CT, USA   USA
Hi there!

I cant help you but I'm interested in your post because I am sort of in the same position as you--with seeming the same scooter. My brother gave me his 1965 Sprint (VLB1) project to put together. After finding many "discrepancies"--and ordering a bunch of the "correct" replacement parts--I discovered that it was in fact a 1965 Motovespa Sprint (150S?). Where are you finding your specs, parts, etc.? Is there a shop manual out there? I definitely need a float needle, carb gaskets, and some other missing parts--before even attempting to start it. Not to mention adjust carb, timing, etc. Wherrver you're getting your info and parts would be of great interest to me...

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ross80 Ross Jenkins
Grevinge, Denmark, Denmark   DNK
Hi there, thanks for the message. Problem with this bike is that so much of it is peculiar to the Spanish Vespa, so virtually nothing is a straight swap - if it were, I could have easily substituted parts from my VBB which would narrow down the list of possible problems. I found a NOS Dellorto carburettor on Ebay in France, which I have since fitted but it still refuses to play ball.

As far as spec is concerned it appears to be like a cross between an Italian Sprint with the earlier VNA type piston-ported engine (not rotary valve like the later Italians). It's a bit of a learning curve for me too as most of my experience is primarily with shaft-drive (LD) Lambrettas. I've built Vespa VBB engines from scratch though, and found them pretty easy by comparison, but this Spaniard is gonna have me committed !!!

It appears I'm not the only person who's had problems with Spanish Vespas - a specialist here in Scandinavia has one in his shop which has been there for years cause he can't get it to go properly, despite having tried everything including electronic ignition.

Someone in the past has replaced the steel insert in the cylinder head for a long 3/8" spark plug; so I put in a new long reach spark plug - which made it start first kick for a while, it would run, but then cut out shortly after; now it's back to not starting at all. Or exploding in the carburettor. I have replaced the wiring harness, junction box, HT coil and lead, points, condenser, plug, plug cap, timed to 27deg as original, new oil seals, engine taken apart to have a cracked transfer port welded professionally, new cylinder studs (originals sheared under the recommended shop torque setting), gaskets, head and barrel lapped together with paste for a perfect seal, compression is good.

Fuel is getting there as the plug is wet, I've tried 2 different fuel tanks and taps, both running clear and fast enough, so fuel starvation is probably not the problem. Annoying!!!

As far as carburettor parts go, here is a website (since you're in the States). The carburettor is a Dellorto UA 19 S1, 60 pilot jet, 82 main jet, 7g float, 255 atomizer.

There are also a couple of Spanish websites I've used for spares; and

Let me know if you need any more info winking smiley

amstrum Mark Strumolo
Naugatuck, CT, USA   USA
Thanks for passing that along. I have far less (none!) experience on the scooters, so I'm sure I will have plenty of questions once I get further along on this's mostly scraping and cleaning at this point!

amstrum Mark Strumolo
Naugatuck, CT, USA   USA
Hey there!

I'm slowly getting closer to attempting to start my Motovespa. Success or not will determine what my next moves will (or won't) be.

In the meantime, I've got a couple quick questions about a couple of the ua 19 s1 carb parts that I need. I definitely need a new throttle needle, which has "C2V" stamped on it. I am not finding any such number anywhere. In addition, I need a new float needle. Likewise, I dont have a part number and dont know where to find the correct one of those.

Do you have part numbers for these and/or sources where I might be able to get my hands on them?

FYI: the throttle needle plating seems to be peeling. It looks otherwise straight and relatively unworn. Do you think I could buff the plating off and use it either as is or replate it?

By the way, how is your project going?



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