Modern Vespa

This is a 2013 Genuine Buddy 125 so not sure if this is the appropriate forum section but anyway...

I bought it for the wifey last weekend. Scooter for Wifey (Post 2656996)
The seller told me the last time it ran was June 2023 (last year) and she practically told me I can have it for $1,000, when she was originally asking for $2k.

So the battery seemed good. I opened the filter cover and sprayed some starter fluid so it would start, run for about 10s and dies.

Took the carb out and cleaned it. It wasn't that bad except the small jet was clogged.

Put it all back and it does the same thing - it runs for a few seconds and dies.

The sparkplug is good, btw.

Any ideas?

Probably has bad gas in the fuel system.

Drain the fuel system, add fresh gas and try again

There was little gas and I added about half a gallon.

Just noticed this, something is missing, isn't it?

We might have to agree to disagree.
Unless that Buddy was fueled in Mexico...way down a dirt road in Mexico, and sold in colored soda bottles, it's not the gas.

O.S.

Nothing is missing there. I have the same setup on mine. It's got a bonded plug in it.

I got a lovely tankful of ick from a local Chevron, during the holidays. I know it was from that station as I'd just pulled the tank and cleaned it, replaced the fuel pump and the filter about a month prior.

Really depends on how the station's tanks are maintained.

Well, the general stuff checks out then.

- there's fuel
- there's spark - consistent good spark and the sparkplug was nice and white
- clean carburetor

Tested it with open gas tank cap, no difference.

Pull your fuel filter (circled in blue) and try back flushing it with carb cleaner.

If you pulled the pilot jet, make sure you pulled the mixture screw (left front side of carburetor) and make sure to blast that area with carb cleaner too. Count the turns in to when the screw seats so so you can get it back to that spot when reinstalling it. Be careful, there will be a spring, a small washer and a small O-ring behind that screw

Regarding the mixture screw - I did that and it was just over 4 turns, which seemed very high. According to everything I've read and, there could be an exception for the 2013 model or something..., it should be 2.5 turns. I set it at 2.5 turns. Maybe that's the problem... will check the fuel filter anyway.

How well was it cleaned? Did you pull the jets, emulsion tube and poke out all the holes in them? There's clean, and then there's the clean that these carbs need to idle correctly!! My wife has the same model and it has similar issues whenever it sits.

I would expect a base setting between 1-3/8 and 1-5/8 turn out if everything is properly clean.

What size is the pilot jet?

I cleaned it as much as I thought it was good - yes I puled the jets out, including the one (if that's what's called) that is the mixing screw. Sprayed carb cleaner in all the little holes etc. It didn't look that dirty TBH.

UPDATE: I cleaned the fuel filter too, doesn't take much, which didn't seem dirty either. Now with the help of starter fluid it would start and idle but as soon as I touch the throttle, it dies -- trying to rev it kills it.

No clue, lol. Standard to the model I suppose

When you took out the main jet, you might have needed to push the emulsion tube down out where the main jet fits. There are multiple holes there (like a mixing tube on a Vespa) that need to be cleaned out. An Ernie Ball #10 or #11 string works well for cleaning these openings.

As for the throttle, did you clean the accelerator pump assembly? There's a diaphragm that draws fuel from the bottom of the bowl, that pumps fuel up to a brass jet on the venturi. You need to check the pump separately. Take the bowl off, add fuel to the brown and push the pump rod. It should squirt fuel out through the well on the side of the fuel bowl. If that works, check the hole in the carb body above that fuel well and shoot some carb cleaner up there. You should see some jet through the venturi onto the throttle butterfly.

Yeah man, I did all that. I used copper wire, one strain of it to clean little holes etc.

So if the the throttle kills it, would that narrow it down to a carb problem? I may need to clean it again

Yep! Clean it again.

Poke out #10, 11,12, 23, 25.

Are you getting gas to the carb? Have you checked that?

Not sure how you check that.
When I took the carb out, the bowl was full. When I disconnected the fuel line past the filter on the carb side it leaked a lot. So I assume gas is getting to the carb... Assume is the keyword here. I'm scratching my head too because I'm certain I cleaned the carb right but it was before I cleaned the fuel filter so it might have gotten contaminated again

How do you drain the fuel from the carburetor on this model? The other models carbs have a drain screw, not this one

If no drain screw on the side of the bowl, just take off the 4 screws that hold the bowl on and dump.

No luck guys, now it won't even start and I used up all the starter fluid.

The carburetor is clean, the filter is clean, the spark plug sparks fine and it's the correct gap of 0.7mm.

I played the mix screw too put it back to where originally was - about 4.5 turns out. No difference.

Frustrating!

It's apparently getting gas. How about air? Just a thought.

I have the air filter cover off and the panel with the filter kind of to the side.

And the air filter is clean, and there isn't a varmint nest behind it?

Lol nope

Hey guys, any input would be appreciated.

I think my conclusion at the moment is that there's fuel in the carb, but it doesn't make it to the engine.

Remember that the Buddy is a 4-stroke, so a little more complex than the ol' Vespa/Bajaj motor overall.

You said that it has a good spark, right?

If you kick it over a few times and then pull the spark plug, is the plug wet or dry? That's the ultimate measure for if fuel is getting into the cylinder.

It's dry.

If there's fuel in the float bowl, you can try to get some into the intake by rolling the throttle open several times prior to cranking the engine. This actuates the accelerator pump. If it's clean and there's fuel in the float bowl, the brass jet in the inlet of the venturi will shoot a jet of fuel down into the intake side of the carburetor. You can take the air filter tube off the carb to check if it's operating.

Roll the throttle 3-4 times before hitting the starter and see if the engine tries to start.

Will do. Any idea about "vacuum" leaks? I'm thinking fuel makes it to the carb but not going anywhere after that

I'm no expert on carbs but I would check that the needle in the float bowl isn't sticking.

The fuel taps are vacuum operated. If you have a vacuum leak, your fuel tap won't open and the carb won't get fuel.

Quick test to do in a well ventilated area is to disconnect the fuel line from the carb and crank over the motor. If the system is working, fuel will dribble out the hose. Don't need to worry about spraying or high pressure!

If fuel isn't leaving the float bowl, the jets or the valves are keeping it from entering the cylinder.

Confirm fuel flow first, fuel to the carb second, and then use your starting fluid one last time to see if you can get it to run.

There are too many hoses, filters, valves, and plastic moldings in the way. I would have an anxiety attack trying to work on that.

Unfortunately I had to leave home in a hurry and didn't try starting it again...

But, with the air filter tube off, I rolled the throttle a couple of times, and it's hard to see if the jet squirts but it definitely gets wet. I assume it's fine.

I guess I'm missing something.

There's fuel in the carb bowl and it's either not making it to the engine (hence the dry spark plug) or it's not enough or something. When I was able to start it with the starting fluid it would run really rough for 1-2 seconds and die.

What about the "choke"? I looks like someone serviced the carburetor as the rubber housing over the choke is missing.

And this happens outside the carburetor? If the engine cranks it would "signal" the fuel tap to open?

Tell me about it. Just last summer I got into scooting after I acquired a 1980 Bajaj (long thread here) and I tell you, I don't like this Buddy 125. But I guess I asked for it ie for a cheap scoot that I can service, maintain and in this case it would be nice if I can get it running

The fuel tap has a hose connection to a vacuum source, usually off the intake manifold. Engine cranking opens the fuel tap and when the engine stops, shuts off the fuel. Like an automatic fuel tap.

OK. So either it's not getting enough fuel, or the spark plug is not as good or the choke is toast.

What about the diaphragm in the carburetor? I checked it, it's intact. What does it do/serve?

The diaphragm is the "CV" part of the carb, or "constant velocity". When you roll throttle, it opens the throttle blade at the front of the carb (and fires the accelerator pump if equipped). As engine vacuum increases, the vacuum pulls the slide attached to the diaphragm upwards, affectively regulating the rate at which air and fuel are fed into the engine. It also provides some degree of altitude compensation, adjusting the air and fuel intake based on air pressure at a given altitude. Not as flexible as EFI, but a bit less altitude sensitive than a standard carburetor.

Success.

The only thing I did is take off the cover of the carburetor over the diaphragm and added some grease to the edges to make sure it sat right.

Sprayed some starter fluid and eventually started. It was rough and for a while if I even slightly rolled the throttle it would die.

After awhile the revs went down and it would die. So I played with the idle and muxure screws when the engine was warm (after 20 minutes or so) and adjusted it to my liking.

The weird thing is that at 1-2 turns out of the mixture screw when I rev it it would not go down to normal until I had that screw out to 4 or so turns.

Finally, it's purring like a kitten! Will see how tomorrow will be.

Thank you guys for your help