Dellorto Euro4 - engine dies after a few seconds

Viarelli

New Member
Hi!

I need your help
I can normally fix engines but this time I can't find the cause.

My sons scoter stopped during driving.

Viarelli Monztro BN139QMB Euro4 Dellorto

- carburetor cleaned
- diaphragm carburettor replaced
- Fuelpump replaced
- temp sensor checked and OK
- airvalves x 2 checked and OK
- TPS checked and OK
- spark plug provides sparks

It now starts but dies after a few seconds
It dies when you increase the throttle
It is possible to restart after it dies.
Sparkplugg does not look wet

Reading other threads I now understand that the Euro4 Dellorto (ECS?) is not the best system but that knowledge seems to exist on this forum.

What to check now?
Can it be the ECU?

Thanks for the help in advance

// Tony from Sweden
 
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Viarelli

New Member
Is it possible to measure it?
Spark is also present at a greater distance of 10mm or more
I have measured the 12 volt side and that was OK.
I got unreliable values on the sparkplug side
 

C-Row

Active Member
Is it possible to measure it?
Spark is also present at a greater distance of 10mm or more
I have measured the 12 volt side and that was OK.
I got unreliable values on the sparkplug side
so it sparks over 10 mm?! should be ok then?
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how is the fuel flow from tank valve? does the float bowl fill up and keep full?
 

Viarelli

New Member
Fuel from tank is OK.
But not sure if the fuel level is OK in carburator, but parts looked OK when I cleaned carburator.
This is one thing I need to check
 

Sparky

Well-Known Member
Could be that the float or floatneedle is stuck or does not move freely or that the needle is not closing or opening the inputnippel propperly.
Fuel level in the carburettor can be checked with a transparent tube connected to float bowl nippel and opening te float bowl valve like in the picture below.
The issue is surely not the ignition coil when you have a spark that jumps across 1cm.
Does the fuel vacuum valve deliver enough fuel when you turn over the motor?
Are the filters on the airvalves clean?
Are there no airleaks in in and around the carburettor manifold?
Are there no airleaks in your vacuumhose?
Does the engine light not blink after the engine died?

brandstofniveau in vlotterbak meten.png
 
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Viarelli

New Member
Hi!

Problem is solved.
- Valve clearance on the outlet valve adjusted from 0,05 to 0,09 mm
( instake is 0,01. Outlet has been 0,05mm the last 1000km whithout any issue)
- It looks like the enriched valve maybe was stuck. It now moves as it should

It will be interesting to see if this really was the cause.
 

C-Row

Active Member
Hi!

Problem is solved.
- Valve clearance on the outlet valve adjusted from 0,05 to 0,09 mm
( instake is 0,01. Outlet has been 0,05mm the last 1000km whithout any issue)
- It looks like the enriched valve maybe was stuck. It now moves as it should

It will be interesting to see if this really was the cause.
how did you find that enriched valve was stuck and did you figure stuck open or closed? and to be sure, you mean the electric heated valve that gives starting mixture?
 

Viarelli

New Member
I am not sure that the the " electric heated valve that gives starting mixture" was sticking or not. Lats thing I touched was this valve and the valve cleance and problem was solved at that moment.

New info: Engine stalled during a longer test drive. Low speed fuel mixture screw was then adjusted and now has the scooter worked fine for 2 days.
Maybe this mixture screw was the cause all the time? wheater has been much colder when the problem started. (it is now 2-4 degress )
 

C-Row

Active Member
that's the same route (2,5->3,25) i took with my Kymco's mixture screwu when it got colder here (nights around freezing). after that i discovered that my membrane-operated plunger (that controls the jet needle) had also been sticking/jamming. polished that and treated the membrane with some Ballistol (which claims to "cure/preserve oil resistant rubber") and got a huge improvement.
the membrane-plunger that i ordered was wrong, so had to make do once i got the original out.
 
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