turns out the left/upper cylinder side of the crankcase was FULL of premix and the exhaust on that side was partially filled. The other exhaust had a small pool of fuel in it too.

This atleast means the crank seals are probably fine, its just taken about two weeks for enough fuel to seep through from the filled crankcase to form a droplet under the engine that i could see.

S'funny because i don't think i accidentally left the fuel tap on after i turned the engine off last time i ran it (a couple of weekends ago). But maybe i did, i can't remember. Anyroad, i was thinking of aquavacing the fuel out through the exhaust port but i might take the motor out altogether now and do a more thorough clean and dry mission.

I've already made up some plates and rubber blanks to seal the exhaust ports off for leak testing in future. I'll make the the rest of the leak testing kit whilst the engine is on the bench.
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After years of moaning about immigrants now i am one...