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I'm having some serious issues figuring out my friends Piaggio Fly 150 (same as vespa LX150). When it's comin' down in the revs it pops and sputters, every once in a while you get a puff of black smoke with the sputters. It's also a b**** to start. Once it gets good and warm,if you pull up to a stop light the idle holds for about 2 seconds then dips a little low, then when you pull away from the light it sputters and hesitates then slowly accelerates. I'm killin' myself over this, I HATE VESPAS!!!!!:whip::whip::whip::whip:

So far, I've pulled and cleaned the carb and adjusted the float, pulled the plug (which was clean when I started checking this bike 3 months ago) and it was totally caked in carbon. That kind of supports what smelled like a rich mixture. So I ordered the damn specialty mixture tool from vespa and right now I have the mixture choked off totally lean and it's still sputtering and still running rich. I ran an entire bottle of sea foam through it (injecting it in the carb with a needle) and got tons of yummy smoke, but no change.

I know it ain't a wing, but I also know there's a lot of motorcycle mechs on this forum who have other experience. Please help me, I'm finding it harder and harder to restrain from taking it to the desert with some 12g deer slugs.

BTW, it's a 2009 with 4900 miles :shock:
 

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What shape is the ignition system in? What kind of ignition? Kinda sounds like the older Fords when the brain box started to go bad.
 

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Monkey with a Football
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Float valve leaking?
 

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Float valve leaking?
I checked the float valve when I had the carb out, all was well.
What shape is the ignition system in? What kind of ignition?
????????? Your guess is as good as mine. Looks like an old VW ignition computer mounted on the side with a small coil. I tryed to check the timing as per the "workshop manual" (you guys should see this damn thing, it's written for a kindergardener and every diagnostic suggestion ends in "take it to your autorized dealer") and my timing light won't work on it for whatever reason.
 

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Vintage Rider
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Unfortunately I am not familiar with modern Vespas, and can only recommend your friend get either a vintage Vespa, or a 2 stroke Stella. I built a '71 Vespa from the ground up. No electronics, and in fact, very little electrics. Kick start only. But VERY easy to fix.

Seriously, on so many newer bikes, scooters, cars, pretty much any vehicle with electronics, finding and fixing the problem can be a real PITA. It takes special skills and special tools to troubleshoot this stuff, and the parts are expensive and failure prone. That's why I stick with vintage stuff.

But even though you have been through the carb, it does sound carb related. The only electronics that should be on that scooter is ignition. If you have a nice spark, then the ignition is fine. I would also check the compression just for the heck of it. I have messed with a few bikes for days trying to figure out what was wrong, only to find very low compression. Now I check that first, and if the engine is healthy, I can look elsewhere without having to worry about it. Somehow, there still has to be something wrong with that carb
 

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Well Jerry, this one's for you, you outta get a kick out of it... Reed valve. There's a system called a SAS (secondary air system), it's designed to feed additional air into the exhaust for the catalytic converter for "more efficient pollution control". This system includes a shut off valve (reed valve) that blocks passage of air during deceleration to prevent "undesirable noise". If I disconnect the valve, no more sputtering, hook it up, sputtering. I pulled it apart and cleaned it out... no effect. So now I gotta track down a new one.

I've put about 9 hours into this pig today (and probably a grand total of 30 or 40 hours since may), damn I hope this fixes it :praying:
 

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The symptoms are not unusual for a Vespa that's been sitting. From your description, best guess is a fuel problem that always effects the carb.
Several areas to check AFTER dumping all the gas & remixing fresh (complete with Stabil or equivilent)
After physically making sure the fuel supply line is not obstructed (disconnect and collect the running fuel in a container) While there, pull the hose attach fitting & check the screen between fuel supply line and carb housing. If all is well, proceed into the carb proper.
1. Verify the Float level 2. Is the float leaking? Is there gas inside the float? 3. Remove & inspect both jets (a clogged port in the secondary will result in your description) Remove both jets and soak in carb cleaner then make sure there are no obstructions inside. (For this, I use a 'special tool' called a acupuncture needle)
Exercise Patience, Patience, Patience
Good luck :leprechaun:
 

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One other trick that you might try.......pull the air breather--with the bike running one hand over carb intake---rev to max & choke to near stop then remove your hand.
Give it an opportunity to spit out what ever may be obstructing the fuel flow.
 

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It aint rocket science
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Rudy wrote:
Float valve leaking?
+1,

Even though it looks OK, the ethanol fuel wreaks havoc at times.

JD
 

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maybe the needle seat in upside down
 

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Vespa that's been sitting.
She rides the hell of it, it never sits for more than a weekend. I checked and cleaned the jets when I had the carb out, I have not pulled the vacuum operated petcock and cleaned the filter on it yet, but I will today. I actually tested the float with acetone, so I know it's not leaking.

I do know that she had been running 87 octane the whole time she's owned it (she got it new in '09) and the book specificacally says it must be at least 91 octane. So she's been running that for about 2 months now.

I'm going to play with this SAS valve today and see what happens. I'll also clean that petcock and then prepare for heri keri if that doesn't do it.:smiler:
 

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I would check the vacuum petcock if it is defective it will suck gas into the intake as fast as it can. It also sounds like it might have a tight valve assuming its a 4 stroke? Sounds like a petcock though to me.
 

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Vintage Rider
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blackknytecnc wrote:
Well Jerry, this one's for you, you outta get a kick out of it... Reed valve. There's a system called a SAS (secondary air system), it's designed to feed additional air into the exhaust for the catalytic converter for "more efficient pollution control". This system includes a shut off valve (reed valve) that blocks passage of air during deceleration to prevent "undesirable noise". If I disconnect the valve, no more sputtering, hook it up, sputtering. I pulled it apart and cleaned it out... no effect. So now I gotta track down a new one.

I've put about 9 hours into this pig today (and probably a grand total of 30 or 40 hours since may), damn I hope this fixes it :praying:
If you are talking about an air injection system like the Goldwing has (it's those 4 metal pipes, one going to each end of the cylinder head, connected to a "reed valve" under the air chamber. It even has an "anti backfire valve". GET RID OF IT and plug up any loose ends. These things can really mess up the way an engine runs, and they serve no purpose. I got rid of the one on my Goldwing while I had everything apart doing other repairs to the fuel injection. I have also removed them from several other bikes, including my Vino 125, Ninja 500, and Vulcan 750. Even though they were all working, the bikes run much better without them. Exhaust runs cooler, ans way less popping on deceleration.

These things are the motorcycle version of the "smog pump" called an Air Injection Reactor" system by GM, that were on most '70s cars. Their purpose was to pump air, which contains oxygen, into the exhaust, which was supposed to help burn any unburned fuel that made it out of the combustion chamber, and they did to a point, but they leaned out the exhaust, caused it to overheat, and caused a lean backfire. Again, get rid of the entire system. It's nothing but EPA crap.
 

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That has happened to my 2 stroke '71 Vespa, but all modern Vespas are 4 stroke. However, if it has a catalytic exhaust, it could very well be plugged up. Many companies make aftermarket exhausts for that scooter, without the emissions crap.

But if it is the air injection system, just get rid of it. It serves no purpose other than to meet EPA requirements so the scooter can be sold here.
 
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