Reply To: bottom cylinder fouling Big Twin 25hp

[Don]

Am assuming the new head is back on now….If not, did you compare the new and original heads? Perhaps there is some difference or flaw in the new head….
It just seems unlikely that with all this stuff going on the engine runs “OK”, even though it is hard to start. Normally, all the oil on the mag plate would foul the points, but your engine has the modules so I wouldn’t think the ignition would be affected by the oil.
I’m pretty sure this engine uses the strange upper seal system that does not have an oring around the upper bearing, relying on intake vacuum to pull oil away from the mag plate. Others will know for sure whether or not this engine has this strange system. Does it look like the powerhead has been split apart before? If so, perhaps someone mistakenly installed the oring on the upper bearing which is a big mistake. I suppose it is possible that all this excess oil is being pulled down into the intake manifold and into one of the cylinders. Please don’t rip this engine apart based on my theories…
You have got a lot going on here, so many possibilities for confusion here. I don’t know much about those atom modules, so that is another source of confusion. You mentioned checking the overboard drain system, are you sure the drain in the bottom of the crankcase is open?
Again, you have got alot going on here, many sources for confusion. Might be best to start over from the beginning… Perhaps figuring out why the engine is hard starting….