Modern Vespa

Hi all,

Been lurking the forum for a while looking for possible solutions to my problem, but I thought it would be helpful to get some personalized advice.

The scooter is a 2007 Vespa LX150, approximately 8,500 miles. I rode it a lot in college, but left it in my parent's garage for about 4 years when I moved to the UK. Now that I'm back in the States I've been trying to get it to start with no luck so far.

Before trying to start the scooter I left the old battery on a Battery Tender, pumped out as much of the old fuel as I could and added half a tank of fresh gas. The oil levels as measured by the dip-sticks looked good, but I imagine this old oil will eventually need to be replaced.

At first, the engine wouldn't turn over at all. I measured only 10 volts between the positive and negative terminals of the old battery which led to me purchasing a new battery. With the new battery charged and installed, the engine would turn over but wouldn't start running. On the advice of another post I found here I tried cleaning out the slow-jet by taking off the float-bowl, unscrewing the jet, soaking it in Seafoam and blowing it out until I could see light through it. Still no start, so I figured it was a fuel problem. I took the fuel-line off the fuel-tap and gas flowed from the tap when I hit the ignition button (and didn't flow when I wasn't trying to start the scoot). I went ahead and replaced the fuel-line between the tap and the carb just in case, but no luck. Some of the clear-plastic lines seem a little brittle, but I haven't spotted any cracks in any of them. I've also tried taking off the air-intake hose and using some starting-fluid spray. The starting-fluid spray will start the engine for a second or two until the ether burns off, at which point the engine dies.

Is it possible I'm getting a big enough spark to ignite the starter-fluid, but not the gasoline? Are there any other parts of the carb I should try cleaning? I noticed the main-jet looked a bit dirty, but would this affect the engine starting? Also, I'm not sure it would stop the engine from starting, but I tried depressing the accelerator pump with my finger when the carb was disassembled and only got a faint gurgle; is this normal?

My plan is to try cleaning the carb a bit more, and then maybe check out the air filter. Even if the air filter is dirty, I'm figuring there must be additional problems since the engine would not start with the air-intake hose disconnected from the carb. Are there any other parts of the carb I should focus my attention on? If fuel is flowing to the carb at the appropriate time, are there any other possibly-cracked hoses that might be stopping my scoot from starting?

Thank you so much for your help!

Verify pilot fuel passageway port in the throttle bore is not obstructed. A twist-tie wire or small paperclip wire may aid in clearing any port obstruction.

Might also be prudent to inspect the muffler outlet and inlet filter housing for nesting insect obstructions.

Your battery will be dead so I'd just replace it and charge it before trying to start again. If that doesn't work I'd replace all the fuel and vacuum lines - if there's a crack in any of the vacuum lines then it won't draw fuel properly. If it still won't start I'd look at the plug - if it smells of petrol after starting it then it's probably an electrical issue so see if you get a spark while holding the spark plug against the side of the engine while trying to start. If it doesn't smell of fuel then it's more likely to be a carb issue.

PS I'm no mechanic but that's just how I'd go about it.

Good plan. Try that and report back.

You have spark, you have compression. What you are lacking is fuel - verified by running, however briefly, with starter fluid. Pull the carb and clean it good. Replace any parts as needed. Replace the fuel and vacuum lines even if they look good. Make sure you got every bit of the old fuel out the tank and carb bowl. Get it back together and check the fuel tap for proper operation by putting it under vacuum. Look at the fuel flow while it is under vacuum to make sure the tap is not all gummed up. Hook it all back up and fire it up. As soon as it warms up, change your oil, check your tires, etc... and go for a ride.

Thanks for the suggestions, all!

Here's my checklist for this weekend:

1. Further carb cleaning
2. Check pilot fuel passageway port
3. Replace other fuel and vacuum lines
4. Inspect muffler (my dad just found a mouse nest in his car, so it's entirely possible I have one in the Vespa as well)
5. Clean air filter
6. Put fuel-tap under vacuum to test

I'll give these a try and report back on any success/failure ASAP!

Good man, let us know how it goes.

I'd expect to do this twice before it'll run decently:
Carb and Jet Cleaning 125/150/200 engines.


Also I'd keep the battery on the battery tender between starting attempts.

If cleaning the carb once is good, cleaning it three times is better.

When I took the carb apart for the second time, I noticed the slow-jet was clogged again; so I went through another 2 rounds of soaking both jets in carb-cleaner, blowing them out with compressed air, and attempting to start. On the third attempt, the engine slowly chugged into life. Let it idle for 5 minutes, and then took it for a spin around the neighborhood.

Thanks again everyone for your help!

Great, good for you!

Here's some storage suggestions to follow before your next travels;
Winterizing Your Scooter

Good man. When get a chance, take a good look at the tires, drive belt and rollers. Enjoy!

I have the same bike with almost 39,000 miles. Anyway the hoses that need to be changed are the fuel and vacuum lines. You can't tell by looking at them but below is a pic of what mine did in 2011 when we swapped them out. Have changed them twice (every 4yrs) on mine. What color is your scoot? Got any pics? Good luck

The fuel hose was actually the first hose I replaced. The second was the fuel-overflow; evidently those clear plastic lines get really brittle when exposed to gas or gas fumes! I haven't replaced the vacuum hose yet, but it's definitely next on the list.

My Vespa is Dragon Red. I don't have any photos on hand, but here's a screen-cap from the video excitedly sent to my wife when I got it running again.

Hey guys, have been really appreciating this forum for helping me nurse an old neglected LX150 back to life, and now working on a 2006 LX50 that came to California from the East Coast and also was neglected.

The bike had been sitting for 6-12 months. I drained all the old gas, and cleaned the carb. Bike would bog down when I tried to go anything past 1/3 throttle so expected it was a clogged main jet, after more cleaning I still couldn't resolve this, so I replaced the carb with a 50cc carb from Amazon. Input/Output measurements look to be the same, and the electric choke plugs in fine. I also replaced the spark plug (old one was looking very black and sooty).

The issue I now have is I can only start the bike by spraying ether into the carb, or by blocking part of the carb entrance with my hand (this helps choke?) when cranking the engine. Once running, the bike seems to be fine, I can hear the electric choke ease off as it warms. I can easily start it again when warm. But can't get it started again without taking one of these extra measures when cold.

Does anyone know why the bike won't start on it's own when cold? I guess can narrow this down to fuel delivery and try some new hoses then fuel tap? If I disconnect the fuel line, how much fuel should come out when I run the starter? How much when sucking on the vacuum with max pressure?

Thanks for your help!!

Get the correct carburetor and you should solve your problem. Just because the measurements are the same, doesn't mean they are the same carburetor.
I don't know anyone who has really been successful getting Vespa engines to run with the Chinese carbs. I do know a lot of people who have tried. The one person I know who has one still complains about a dead spot when you roll on the throttle.

more info needed.

post a link to the carb you sourced.
what main jet did it come with?
what was your old main jet?
what needle setting are you using?
what was your old needle setting?
have you tested the electric choke to ensure it is fully closing properly?
is the butterfly for the choke hanging up?

Thanks for the thoughts guys! I guess I could put the original carb back on and see if at least the starting issue is solved, even if it still bogs down at full throttle.

New carb I'm testing with is the 'GOOFIT PD18 18mm Carburetor for 4 Stroke GY6 49cc 50cc. Fit for 4 stroke GY6 49cc 50cc engine, electric Choke (plug style): 2-pin male plug. Intake Manifold side: 18mm (Inner Diameter),Intake Manifold side: 28mm (Outer Diameter) Main jet size:75#, Air Filter Intake:35mm(inner diameter), 39mm (Outer Diameter). http://a.co/d/6Ency41 It runs fine once it's going, but no cold start.

How can I test the electric choke? Not sure about butterfly and needle settings? Anywhere you can point me to more resources on troubleshooting the carb for starting would be great!

If the bike runs fine once going, I should rule out any fuel delivery issues with the fuel/vacuum hoses and tap?

Thanks again!

Update. I put the original carb back on and seem to have resolved the cold starting issues (I wonder what made the Amazon carb not start properly?).

Now I'm just trying to resolve the original issue: loss of power anywhere past 1/3 throttle. This does seem to be a main jet issue? If I've already cleaned the carb a few times, should I just order a new main jet? Anything else I should be considering/cleaning in the carb?

I also noticed today that the bike backfires when idling down hills or coming to a stop on idle (maybe 15% of the time). At least I think this is what a 50cc Vespa backfire sounds like (like a small puff of compressed air?).

Thanks again for all guidance!