M15D2 Excess Fuel in Lower Cylinder

[tmccaffery]

My 5 year old M15D2 is getting too much fuel in the lower cylinder which is causing the spark plug to foul, low power and problems at idle. My mechanic has overhauled the carburetor and fuel pump but this has not corrected the issue. While we are scratching our heads over this issue any advice or suggestions would be appreciated.

 

[pvanv]

Did you verify ignition?

 

[tmccaffery]

The mechanic said he has, but I will double check. He has changed out all of the electrical end (plugs, coil & etc.) except for magneto with no change. The engine starts, quits when it is in idle for longer than 10 seconds or so and won't develop full power at full throttle. The upper cylinder and plug is clean while the lower cylinder/plug is dirty.

 

[pvanv]

What exactly did he do to the carb?

 

[tmccaffery]

He cleaned and re-built the carb with the carb rebuild kit, as well as cleaning & etc. the fuel pump, and says that it is working correctly now. He is currently thinking that there might one, or both, of the inlet manifold gaskets may be leaking.

 

[Mc Tool]

Broken reed valve petal ?

 

[tmccaffery]

We looked at the reed valves yesterday and they are intact. The only odd thing is that both cylinders are firing at the same time about every second or third firing cycle. Since the exciter coil has not been replaced I have one on order. Also, the lower crankshaft seal may have been leaking as some oil was found in the engine base. Unfortunately, due to the approach of Hurricane Milton he's not going to be able to do anything further until next week, by which time I hope the new exciter coil is on hand.

 

[Mc Tool]

Both pots will fire at the same time . Its called wasted spark . Rather than have a sensor for each pot they have only one and it fires the (dual )coil every 180 deg with one plug sparking harmlessly at BDC. When testing for spark both plugs need to be earthed or neither of them will spark.
I am just resurrecting a M18d ( got it for free ..... which was way to much )