[Masteryota]

Um, well I can't say I totally agree with the kerosene, but I do agree you should be careful about any type of deposits or oil sludge.

@slestak. I was with toyota at the end of their infamous oil gel issues in the late 2000's, and knowing we were putting short blocks or rebuilding the bottom end in these vehicles, we tried any number of things to break loose the gel/sludge in the head to help with the cleaning process, and the only thing that helped was ATF. Conventional motor oil is by nature high in detergents, and ATF has similar agents added to it to keep sediment from building up, but these cleaning effects take time to really clean it out, and you don't want to run an ATF/oil mix for long periods, as the ATF breaks down much faster than the oil.

@zman, I would use a high quality oil, whether synthetic or not, and change it twice as often for the first few months. I might stay away from synthetic at first, both for the price and frequency of the oil changes, and if nothing else makes noise or comes apart, then I might switch.

Also, running the engine without a muffler will cause it to run lean, and lean is hot, inspect the valves closely, you might see some burning on the seats and face as well, that would confirm your diagnosis.