150cc stuttering when warm By jim150 (Read 1,894 times)

[jim150]

I am trying to figure out a problem with a friends 150cc GY6 scooter.

The problem occurs when the scooter is warmed up. The engine will sputter and miss. It is almost like the ignition is being cut out as you are on the throttle. It will start fine, idle fine and rev when its cold. when it warms up the problem occurs.

here is what I have done.

replaced reg rectifier because it was fried now is wthin spec
new battery because reg/rectifier toasted it.
oil change
spark plug
new plug boot
tried new CDI, no change
adjusted carb air srew and shimmed needle both to rich and lean,
no change.

I am running out of options here. I have not pulled carb, but if a jet was clogged i would have problems when cold too.

I have not adjusted the valves, but again, I have no reason to believe they are out of adjustment because the engine doesn't die at idle or seem to have any compression problems.

I have one last theory and it involves a an extra ground wire on the reg/rectifier. Ther is a black wire grounded there and a green wire grounded there. I am wondering if that wire might go somewhere else??

Any help is appreciated.

[Kaveman]

The idle when it first starts is higher due to the auto choke . My scoot also does run abit rougher when the engine gets fully warmed up at lower idle . You might adjust up the idle speed screw( not the air fuel screw) , where the throttle cable ends, on the carb to idle abit faster . The issue you are having isn't something to worry about (extremly) .
willc.

[sprocket]

OK..when it is cold it revs OK???.. this means the enricher is open...and the fuel/air mixture is rich for cold running....

When the enricher closes it leans the mixture and your problem starts...

So check that the enricher is working. If it is working then adjust your air/fuel on a hot engine like after running 5 minutes...

If that doesn't work the main jet is likely plugged and the carb must be cleaned and wire run through the jets..

[Kaveman]

One more quick note . The idle will continue to do what its doing reguardless of a new cdi and sparkplug and other ignition related upgrades. What your expierencing could be typical of the engine ( similar to mine).
will c.

[jim150]

Thank you both for your answers but I forgot to mention I replaced original enricher. I tested the original and it works. The new one has been tested and still no change.

Forgot to mention that in my orginal post.

That was one of the first things that I suspected.

[sprocket]

OK your enricher is working... then adjust your air/fuel mixture screw. That doesn't work either clean the carb.

Kaveman this is not typical.. the engine if tuned correctly will have a very smooth power curve with no sputtering...