Reply To: bottom cylinder fouling Big Twin 25hp

[The red boat]

it was running well all summer but it was getting harder and harder to start.
per my first post on this thread I went to change out the spark plugs and somehow managed to strip the bottom hole.
So I put on a NOS head and it hasn’t run worth a darn since then and is fouling the bottom cylinder and plug.

I’ve removed the NOS head and am now trying to replace/clean everything I can while avoiding cracking the case open as a last resort.
I’m going to put on the original head and use a helicoil in the bottom hole since I know it ran fine with the original head.

I was surprised to see that I had parts missing from my upper seal and that there was quite a bit of oil on the mag plate. My first thought was that the excess oil was messing with my ignition system and causing weak spark on the bottom cylinder or that the ignition module for that cylinder was not working perfectly.
then i saw there was oil inside the cur-out vacuum tubing and thought it may have had an effect on the cut-out switch too. That could just be from excess unburned fuel tho.