I sold my '85 XR600R to my buddy in '93. On his second outing to Glamis he went over the bars and knocked his two front teeth out. The bike has sat in his garage unstarted since then (10 years). I have been bugging him over the years to sell it back to me as a spare bike. He finally relented a couple of months ago and it's in my garage now. The bike's in really good shape cosmetically. I have replaced almost every part in both carbs - jets, needles, needle valves, etc. (bikebandit.com loves my money). I couldn't get any spark, so I got out my tester and found I had to replace the pulse generator. I finally got spark but it was weak so I put in a Ricky Stator. Spark seems fine now. Fortunately, my buddy had drained the tank before he stored it. It still had a bunch of dried up varnish chunks in the bottom. I rinsed and scraped the tank out a few times with a long screwdriver and got the junk out of it. I took out the petcock and cleaned the screen out. I got it to fire today, but it is hard to keep running without the choke on. It dies when I twist the throttle quickly unless the rpm's are up kinda high. It is popping a bit when I back off on the throttle. It is responding to adjustments to the air screw but I can't seem to find the right adjustment to get rid of the popping. When I rode it down the street to put a load on the engine, it started popping a lot and died when I let off the gas. I definitely am not the most knowledgeable mechanic out there. Am I doing something wrong? Should I be looking elsewhere like the valve clearances (which I haven't checked yet)? Any thoughts?