I have a 2009 Yamaha 15Hp Enduro 2stroke, well maintained. When operating it just above idle speed, the engine
mis-fires (runs rough). Upon opening the throttle to get on the plane, the engine
hesitates/mis-fires acouple of times, and then takes off.
When operating at 1/2 to Full throttle, it performs 100% and no mis-firing.
I also notice a lot of wet oily deposit at the rear outlet opening on the outside of the upper drive casing. The manual states 50:1 oil
mixture for this Enduro model, and 100:1 for the more "civilised" 15Hp model, which are identical in specification. I have reduced the oil
to 75:1, but no improvement.
New spark plugs (acc to manuf specs) made no diffirence.
Any suggestions/similar problems?