Hi all,

Just wanted to know if this is as wrong as I think it is...started my new four stroke (YS110), and on the VERY FIRST RUN (needle settings as per instructions) it wouldn't run consistently, and the exhaust was black! I normally associate black exhaust with either i) too lean running, or ii) normal in break in process, after a couple of tanks - clears up again in this case.

Could it have been bad stuff left over from manufacturing in the combustion chamber?

Cheers,
Ken

probally the fine bit of metal that you would find in a new or rebuilt motor just being expelled out the muffler copule more tanks on a rich setting should clear up

Certainly a bit (or bits) of metal in the bore will give you this. If it doesn't clear up by about the 4th tankful, refer to the store where you bought the motor. You could have somehting not nice going on inside.

Don't be surprised to have to change your glow plug. Bits of fine metal flying around in the bore can destroy the plug element.

black is also often a sign of the muffler joints moving a little bit, either the sections of the muffler itself or where it attaches to the engine.