Backfire through the carbs? or something else?
 

My bike has made the same very loud cracking almost metallic backfire noise accompanied by plenty of smoke twice now. the first time it was sitting still on a stand in first idleing, I shut it off immediately but upon thorough inspection found nothing wrong put it all back and rode just fine for a month and about 500 miles then it made the same noise tonight as I got back from a ride and idled it to the shed. the smoke and noise seem to be coming from the back of the motor and or the exhaust in that area. Any thoughts or comments are welcome and appreciated.

thats dfinitely not a backfire through the carbs, if it spits out the carbs it will make a "poof" sorta sound and you'll hear the slide slam all the way up then it will go back to running normal, generally it's associated with a lean condition. A loud metallic cracking sound with a lot of smoke sounds like something serious is letting loose to me, tough to say without actually hearing it/seeing it in person, maybe someone more familiar with the hawks will know though...

It happened again today it's always while idling. I noticed the oil view window looked foggy. when I opened the oil fill out came the smoke. The bike started right back up and ran fine. any ideas? anyone?

Make sure your breather hoses at the top of the heads are clear to the airbox. Inspect the airbox - if there's lots of oil, you have a crankcase breather problem or the beginning signs of a motor that is about to blow its rings. Pull your plugs and see if they're oiled up. Make sure you're maintaining proper oil level between changes.

Thanks I'll do that, I was thinking of checking the compression.