Hey everyone,
This is my first forum post, so apologies if I’m missing something!
I’m working on a 2000 Yamaha 15FMH 2-stroke outboard, and I’m having trouble getting it to run properly. It doesn’t idle at all, even with the idle screw turned fully out and the air screw 1.5 turns out. It usually starts within 3 pulls, but once running, it won’t hold idle — I have to give it throttle or it stalls.
I cleaned the carb thoroughly, so it should be clean inside. I also resealed the reed valve with gasket sealant to make sure there are no air leaks.
I pulled the spark plugs and saw a clear difference:
Top cylinder plug looks perfect — nice coffee-brown color.
Bottom cylinder plug looks almost white or beige — possibly running lean?
Could this be:
A vacuum or air leak affecting the bottom cylinder?
A carburetor issue affecting fuel delivery to the lower cylinder?
Ignition-related (weak spark)?
Any advice or tips would be greatly appreciated. Thanks in advance!
This is my first forum post, so apologies if I’m missing something!
I’m working on a 2000 Yamaha 15FMH 2-stroke outboard, and I’m having trouble getting it to run properly. It doesn’t idle at all, even with the idle screw turned fully out and the air screw 1.5 turns out. It usually starts within 3 pulls, but once running, it won’t hold idle — I have to give it throttle or it stalls.
I cleaned the carb thoroughly, so it should be clean inside. I also resealed the reed valve with gasket sealant to make sure there are no air leaks.
I pulled the spark plugs and saw a clear difference:
Top cylinder plug looks perfect — nice coffee-brown color.
Bottom cylinder plug looks almost white or beige — possibly running lean?
Could this be:
A vacuum or air leak affecting the bottom cylinder?
A carburetor issue affecting fuel delivery to the lower cylinder?
Ignition-related (weak spark)?
Any advice or tips would be greatly appreciated. Thanks in advance!
