Grey smoke

[fixerupper]

So I picked up a steal, a 1984 XJ 600 for 400$ and my old Honda MB50. it was a no runner at the time and the guy didnt want to put any more time into it. after some tinkering and testing it turns ohe exhaust camshaft was out by 90 degrees. after rotating it back and lining everything up (the valves were still intact luckily) It was still running a tad rough. my local mechanic says theres a hairline crack in the rocker cover, and the float needles need replacing as they are letting a little too much fuel into the carbs. the bike starts, but runs a little roughly at idle, and grey smoke pours out of the exhaust, keep in mind that this model is aircooled. So I'm stumped

any help or advice is welcome