yamaha aerox 50 non starter

janet.boddy RemoveThis @btinternet.com wrote:
>Hi
>My son has been given a Yamaha Aerox 50 to work on as it won't start.
>Its a 54 model. We have taken the casings off and checked that the
>piston is moving. It isnt seized. Put a new spark plug in but the
>spark still looks weak. It turns over with the electric start but wont
>fire.

Weak looking spark doesn't mean much because low horsepower engines will
start up on the weakest spark you can see. If you have sparks occurring
regularly, the CDI is OK, don't let anybody sell you a new one.

Maybe setting the spark plug gap to about 0.022 inches will help a little.

What year was your son's YQ50 made?

What kind of carburetor does it have?

The non-starting problem is usually a dirty carburetor which has gotten all
gummed up deep inside from the motorcycle not being ridden for a long time.

Weak idle mixture has a greater effect on the engine not starting than weak
spark.

There are clear aerosol chemical carburetor cleaners that contain toluene,
acetone, benzene, methyl alcohol, etc, which will clean the gum out of the
idle jets. The names vary from country to country.

Riders in the UK have mentioned "Redline" carburetor cleaner, but we don't
have that brand here.

Once the carburetor is all cleaned out and no more nasty brown stuff comes
out of it when you spray the aerosol through all the passages, turn the idle
speed screw all the way out and try to start the engine without turning the
throttle handle.

Some scooter carburetors, like the Gurtner PY-12 which is used on 2007 Aerox
50's have an electric choke solenoid. If the wiring connections are all dirty
and corroded, the electric choke won't work.

It is also possible that there is a damaged petal in the reed valve that
allows air to flow backwards through the carburetor when he tries to start it.
But you can feel the air pushing backwards when you hold your hand over the
carburetor inlet if the reed valve is damaged.

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