Here are some details on the bike...1999 TW200, bought from original owner, my brother. Garage kept, used on small farm, has about 3500 miles. Gently ridden thru its life. Bike has sat for about 4 years, had rusted tank. Here is what I have just replaced: New Clark fuel tank, fuel petcock, gel battery, new air filter...removed the carb for a complete cleaning. When everything was put back together, the bike was hard to start....once started it ran fine, idled great, but was hard to start the next morning. I removed the carb again, and cleaned the idle circuit, all jets and passageways a second time, reinstalled and it starts right up instantly and idle and revs perfect with the choke pulled out. With the choke back in, it still idles down fine, but when revving, it falls on its face until wot. Bike can sit overnight and start instantly the next morning with the choke again, but still has the dead spot when cracking the throttle, no choke...i can feather the throttle and it is fine. I pulled the plug, and it is a nice clean tan color...previously after the first rebuild, it was black, carbon fouled...now the plug is clean. I hate to pull the carb a 3rd time....Can there be a possible vacuum leak somewhere? Any trouble spots to look for? Fuel cap not venting? Lots of threads similar to this, but most had idle problems...this bike idles great with choke on or off....just will not rev smooth off choke, and the plug is clean? Also, I have a cracked plug wire boot, the hard plastic that snaps onto the plug...when I unplug it and lay it by the plug, it has good steady spark, but could this be missing out causing a misfire? Thanks for any help/advise.