2005 WR450F, purchased used last year. Pretty much stock except for a PMB exhaust insert, red anodized fuel mixture screw (zipty?), and AIS removed. Ran ok for a year at 200-5000 ft altitude but seemed to need the fuel screw backed out too far, 3-4 turns at sea level. No pop on deceleration. This week I pulled the float bowl to check the jets and found a 168 main and a 48 pilot. Also found the clamp between the carb and the cylinder was loose. Put it back together and it seemed to run great up the hill for 1 mile and then died. Now will not start or idle, hot or cold, without the choke. Will hold mid and high rpm with the choke pushed in but runs rough and pops. I have pulled the carb off three times. Cleaned the air filter. Replaced the pilot jet one time because on the second look, it was a little clogged. The carb bowl smells a little bit like varnish but is visually clean. I replaced the aluminum mixture screw with a Scotts and a new o-ring. I either lost the original o-ring during all this disassembly or it was never there. I have hit it with a can of carb cleaner and compressed air. I concentrated on the passages between the pilot jet, the mixture screw, and into the carb. When I squirt cleaner into one place, it comes out the other two places. Any ideas what to try next?