My Commando 'wet sumps' if left standing and I agree that some Harley engines do the same. Upon starting the oil pump then attempts to empty the oil sump and spits it out through the breather. In the case of the Norton Commando, I drain the oil after a winter standing and then refill from the top.
Hope this helps
Jethro
Connaught Morgan 4/4, Norton Commando, Guzzi V35 Imola, Velocette LE, BMW C1, BMW C650 GT
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