Modern Vespa

My LX50 starts to run rough and cuts out at lights after about 15 minutes. This happens every time I take it out - I live in a small town so have put up with it because I get everywhere in under 15 minutes !

The reason I think it is overheating is that the exhaust gets blisteringly hot and the smoke coming out smells burned, and is bluish. (ed. I suppose that could mean it is running 'lean' - from my model aeroplane days - is there such a thing as a mix adjustment on my LX?)

Its time to sort it out - its over 12 months now and I am sure it is not doing the engine any good. It has done 1000km.

I cleaned the carburettor (it looked spotless) . I suspected an oil feed problem - so I premixed but it has not made a difference.

The only thing I can think of is maybe a fan problem - does my bike have a cooling fan even?

If anyone can help I am all ears ...

The only thing I can think of which may have happened to cause this is that it has blown over 2 or 3 times since I got it 3 years ago - and I am not sure but maybe the problem coincided with one of these falls.

I am using 100% synthetic oil - that isn't it, is it?

thanks

When was the carb last cleaned? I'd be looking at adjusting the idle mixture. Manual here (Ok, it's the US version, but very little difference):
http://www.wotmeworry.org.uk/manuals/More%20Manuals/Vespa/

Not sure the 4T carb in that online manual is the same as mine .. but I cleaned the carb recently. Is the idle mixture setting the same as the idle revs setting screw?

I was reading about the LVAP pipe - but I do not understand - isn't the vacuum needed to open the fuel supply valve (its the pipe I suck in order to get the fuel to flow out the fuel tank?)

Or does the 2T not have an EVAP pipe? (its a french LX50 by the way)

thanks

You won't have an EVAP hose, and the evap hose is different from the vacuum fuel tap hose you are referring to. But you don't need to worry about it anyway on a french bike.

Your carb has two adjustment screws, the idle speed screw and the fuel-air mixture screw. Jimc is suggesting your fuel-air mixture screw might be off. Is it a weber carb? I'm sure somewhere on this site someone has identified the two screws on that carb.


And welcome, by the way! Lots of information on this site to be gleaned!

thanks for the welcome

I think there is a screw with a screwdriver slot near the knurled idle adjust - I guess that is it.

I did not mention that the air feed restrictor has been removed (but the problem predates that anyway) , and also I 'think' the dealer did something else - maybe snipped a pipe off the side of the exhaust?? - I am really not sure - he just said he had 'made it a bit faster' ! - could that be making it run lean?

I'm off to fiddle with the mix.

If the dealer de-restricted it he should have re-jetted it as well. This is often neglected.

if he didn't re-jet it could that be the issue then?

It would have you running lean, so I would imagine that could be it!

I needed to adjust the idle speed screw clockwise just over one full turn in order to prevent it cutting out and the mix screw about 1 and a half full turns clockwise to get maximum revs and smooth running. I am pretty sure that this means something else is wrong that I have to adjust these 2 screws by so much - so I think it is time to take her in for a service and thorough check up I think - I will check on the re-jet issue at the same time.

Thanks for all you help.

Carbs wear over time, so it may not be any big issue.

Hi,

Common problem with hot LX50 is poor acceleration from stand.
This may also lead to stopping from idle.
It's mainly an issue of the idle mixture screw.
Normally the LX50 has a Dell'orto 16,5mm carburetor.
In a german forum there were reported very different settings of the idle mix screw for smooth running.
Factory setting ist 1,5 revolition from closed. My wifes runs fine with 1,25, others reported 2,5 as best setting.

How does your spark plug look like? This may give a hint, (but with only 1000km maybe not to much). White (lean) or black (fat) or brown (good).

The spark plug in my wifes LX50 looked like this while the problem of poor acceleration persitst: (a little too lean)


My ET2 (same engine and carburetor) didn't suffer this problem (both bikes have ~ same milage):


Bye

Thanks for the tips. When you say 'closed' I presume you mean turned clockwise all the way , I presume anti-clockwise 'opens' the mix screw?

The 2 times I have checked the plug it was actually very black - which kind of screws up my lean theory!

I appreciate the settings you posted I will try at factory first - it is very hot here so I may try at 1.25 too. But its good to have a reference point so I its not totally guesswork. Thanks.

The bike certainly does 'hesitate' when accelerating hot , but I hope the correct mix setting will help that.

Yes, count the revolutions from starting position "clockwise closed". Be careful when closing, it's fine mechanics.
The Vesa shop told me, that the carb reacts very sensible on the screw and that there is no linear behavior. Also changes on the idle mix screw interfere with the idle speed and vice versa (normally changes in the mix screw also cnge idle speed which normally has to be adjusted by the idle speed screw, etc).

bye

Well things seem OK - I set the mix screw to 1 and a half and adjusted the idle screw when warm - and so far, so good! Also the acceleration from stand is definitely better. I will run her a few weeks and then check the plug color.

Thanks to everyone, I really wish I had joined up 12 months ago ..

Hi, I´ll borrow this thread to get some help about a very similar problem.
Some time ago I bought my LX50 brand new nad I must admit I have only been driving a scooter once before in my life so I did not ahve much to compare with.
First of all my LX50 idle was too low, it stopped even e few times as I tried it just when I got it from the store. The shop selling it to me told me I just have to turn the big knob at the carb clockwise to get the revs up. Simple I thought. Coming home, turning it clockwise did actually making the idle slower, so when I turned it counterclockwise (out) kind of 2 turns It was ok. So I just left it there and the idle has been great after that.
Then I also noticed the flames coming out the exhaust pipe when stopping for a red light with motor running at idle. After that I thought that the flames can mean its runing fat so I thought I have to measured the fuel consumption and it was high, 4,8/100km. Have been runing it 500km by now.
While I did not like this I asked the guy at the Vespa store at two different occations if it was norman with the flames coming out, and he did not react on that, did not say something was not normal.
After some reading on the internet I decided to take out the spark plug to try to find the truth.
Wow, pitch black and wet, including the whole isolator, that should look white with a brownish ring at about two millimeters deep down in the plug. Take a look at the pics.
Then a few days ago, after sending a long email to the Swedish importer SPG Motor and the vespa store when they at last will take it in because they say there is a technical bulletin (013-2011) regardning the exhaust system. But they did not comment what so ever on my questions and pics of the plug, so I am still worried about the engine, I mean, how will this affect the runing in period of the engine?
AND NOW, I did go out to find out how long the idle mix screw was turned from bottom, so, marked the screwdriver position and tried to screw it clockwise (in) to bottom. I cold not!!!!, cos it was already in the bottom!!! My god, I cold not believe it, I was suspecting the reverse that it was turned to far counter clockwise (out) because it ran fat. So, I did now opened it to 1,5 turns nad decided for a short test run.
WOW, its now runing smooth and even, a huge difference from before.

Now to the big question. What shall I request the importer and vespa store ot do for us?

I am very worried that the engine and not at least the exhaust system can have been damaged. The exhaust system was not that hot at my test drive I did today as it have been after all other driving before this adjustment.

On top of this, there is a oil leakage from the spedometer wire where its coming out from the front wheel centre. This oil is dripping on the brake disc, this is not good at all of course.

Please advise me.

Wow. That last post is crackers. Flames coming out of the exhaust! Oil coming out of the speedo cable??? You must let me know if you solved these problems.

The only solution I can think of is replacing the clock battery. Or perhaps adjusting the pressure in your tyres.