Thought I'd pass on what I learned. Most of you probably know this but some probably don't... 1986 XR600 dual carb
"Yeah, so I got crackin' today and pulled the float bowls off... Guess what? they were reversed! No wonder the dang thing wouldn't start and the choke had no effect! I bought some spray carb cleaner, went to work. some crud was in the main jets but nothing too serious. I have 125, 125, 45 as jets btw.
I put it all back together with new allen head bolts, set the air screw to 1 3/8's - which after more research seems to be the setting for a dual carb bike, and it fires right up! She runs really sweet.
How many years have people been fighting this bike b/c someone put the float bowls on the wrong side? Who knows...
...the left bowl has a small brass fitting right below the choke that enters another cavity and is either blocked or opened by the choke lever. The right bowl has the castings but has not been drilled out and the brass fitting is not there."
Hope that helps someone!