Hi all,

So I have the usual starting problems with my '96 Leo 125.
So far I changed/checked:

-valve clearance is good (may be a little too much on the exchaust valves)
-air system is tight, no cracks on the tubes or couplings, air filter is new
-carburetor is cleaned, automatic choke is working well
-new NGK spark plug (also tested with Iridium type), it has good spark
-changed the fuel lines to transparent type to see fuel flow, everything is fine
-fuel lines and intermediate container are not clogged, fuel pump works well

...but the engine would not start easily, if at all.

I'm not sure about the proper carburetor settings.
If I set the throttle valve to fully closed, it would start when cold, but in about 10 seconds the idle goes too low and the engine stops.
If I set the warm idle, then it would not start when cold.

Do you have any suggestions what to adjust or do?

Can it be a carburetor issue?
Or do I have a blown head gasket?

Thanks for the tips in advance,
Alf

first of all, the carburetor ist an original one from 96 ?

Please check the small filter on the "back side" of the carburetor, is it okay ? is the rubber okay ?
Picture http://leonardoforum.de/viewtopic.php?f=6&t=3081&hilit=kleiner+luftfilter

To check the cylinder head gasket : let the scooter stay, the next day :.screw out the spark plug and hold for example closet paper in front of the hole.. start the engine and check the paper ? is there some fluid ? Something that looks like the cooling water ??

Yepp, it's in a good condition, the rubber and the filter as well.

And yes, it's an original carb. But I also have a carb from a Cygnus.

Well, there's something small sign of liquid on the paper, but it does not look or smell like coolant.

...but it does not smell like gasoline as well...what can that be?

What about the CO2 screw, how many rotations is it screw out ?
First screw in completely and count the rotations (after that screw it to the first position)
You find that screw on the top of the carb, I think it is made of brass
http://www.bike-teile.de/pic/aprilia/g/1315135532_vergaser.jpg (at the right top of the carb, don't confuse with the screw for neutral running)

I have tried 1,5 then 2 turns, and even more.
Now it's about 2.

After yesterday, I am still thinking about that liquid marks on the paper... although it does not smell and look like coolant, it can not be anything else. So I'll get a head gasket and replace it.

Hey,

maybe it is the Zylinderhead gasket. You have to check the spark plug. If there is any liquid on it, the gasket is damaged. You can also have a look into the main container of the liquid. Is there any oil oder only liquid...

Fabian

The strange things are
- if I try to start the engine, after 30-40 seconds of continous starting, I can hear that the coolant flowing into the container suddenly
- there is a big pressure in the coolant container even if the engine does not start and the system is totally cold
- I don't see much liquid on the spark plug
- there is no oil in the coolant liquid

ÜBERSETZUNG für DIE DEUTSCHSPRACHIGEN - EINFACH AUF DEUTSCH SCHREIBEN; ICH VERSUCH ES ZU ÜBERSETZEN: Helft dem Burschen mal

Alf hat massive Startschwierigkeiten mit seinem 96er Leo, Original Vergaser, nichts verändert.
- Ventilspiel ok
- Schläuche ok
- Vergaser gereinigt
- neue Zündkerze probiert
- Benzinschläuche erneuert in Durchsichtige, Benzinfluss ok
- BEnzinpumpe gecheckt, ok Zwischentank OK.
- sofern er den Leerlaufregler zu macht, startet der Motor im kalten Zustand,aber nach 10 Sek geht die Drehzahl runter und der Motor stirbt ab.
- Kleiner Filter am Vergaser OK
- er hat noch einen Vergaser vom Cygnus
- er hat eine kleines Spur einer Flüssigkeit auf dem Taschentuch, sofern die KErze raus ist und der den Anlasser kurbeln lässt, es sieht und riecht aber eher nicht nach Kühlflüssigkeit, aber es riecht auch nicht wirklich nach Benzin
- CO2 Schraube auf 1,5 bzw auf 2 Umdrehungen, keine Besserung
- er will ne neue Zylinderkopfdichtung einbauen
- Kühlflüssigkeit ist sauber
WICHTIG :
- Wenn er den Motor startet, hört er nach ca 30-40 Sekunden, dass die Kühlflüssigkeit in den Ausgleichsbehälter läuft, er hat einen riesigen Druck am Ausgleichsbehälter (SOGAR wenn der Motor nicht startet BZW: das ganze System total kalt ist !)
- er sieht ganz ganz wenig "Flüssigkeit" auf der Kerze





@ALF_HUN
- While starting the engine you can leave the coolant container open (be very careful while opening on hot engine). When the liquid gets into the coolant container, that means that the thermostat has opened..
- you need to change the lower gasket also when you replace the head gasket !
- If you have coolant in the cylinder, you should see the color on the paper. it helps to have coloured coolant luquid.
- I hope you have the correct spark plug ?

Hello,


Open the coolant-container an than start starting your engine again. If you can see bubbles in the container, you have an damaged gasket. Sometimes there are also some smoke ... then the gasket is definitely damaged.


that's strange and new for me (try the first point, take a look into the container)


I think that happens only, when the gasket is damaged at the "right" place.

Best regards
from Hamburg

Sounds logical, but how can the thermostat open with a non-running totally cold engine?



Thanks for this information, I didn't know that!
I have a good condition 150 ccm cylinder set (with piston and rings), I think I will put that on when I disassemble the engine.



Yes, if I had coloured coolant, it would help. But I don't.
I will change that after I finished with this problem.



Yes, I have two, brand new plugs, a CR8E and an Iridium.

Hello hansejung,

Thank you, I will check that container and I will let you know.

Cheers,
Alf

Hello Alf,
be careful, you need for the 150ccm cylinder different gaskets than for the 125ccm!

cu

I knew that, but thank you very much anyway.

at last since this point, I'm sure it is the cylinder head gasket. gasoline and oil are clear indentificable, and everything other has to be a liquid from the cooling system, because there is no other liquid at all.

The pressure in the cooling system shows that air runs from the cylinder to the cooling system, and despite the thermostate is closed, the pressure runs to the coolant container through the bypass of the thermostate.