[blueboy5000]

The white powder is a a combination of evaporated gas/gas resins and salt. That's what these carbs look like if they sit for a few years without draining the gas out of them.

I'd pull the carb down and clean it out good, the powder (mostly zinc, salt and magnesium) will rinse off easy with carb spray. Though if you wanna get it super nice and clean, soak all the non-rubber parts in a clean bowl of de-natured alcohol for a couple days.

While it's probably not the best, the powder shouldn't screw up the engine. Though I would immediately change the oil.

Do a compression test (use a TESTER, not your finger). If compression is good, you're probably fine once you get the carb cleaned up.

Also remove the FUEL TANK and FUEL LINES, and REPLACE the lines and clean the tank with fresh gas and carb spray, make sure you clean out the PETCOCK also.