View Full Version : Yamaha 90HP

09-21-2006, 03:36 PM
"the problem is that the upper plug responds very very weak, and causes for backfires and runs leap .

1. i replaced plugs .
2. cheked compretion and all three are good.
3. there is agood spark from the coil (the upper one was good all so ).
4. and the carbs all so was checked .
5. i swap the upper coil with the main and the problem still on
what else can i check"

09-29-2006, 02:01 AM
plug wires or it is the power pack not suppling enough of volts
u should have 100-300 volts to the primary side of the coil