Proud owner of a Standard 2001 WR400. The bike was raced in the French ISDE and has only done 6 days work! I now own the bike and there are two little problems. As the bike comes of the idle, it is hesitant and surges. On full throittle it flys! On the over run as you approach a road junction there is an occasional massive bang and a flame out the back according to my mate who was following me the other day. The plug indicates the bike is running very rich. There are no leaks around the exhaust that could cause the bang (back fire). It was suggested that i should check the diaphrams in the carb for any dust / muck or water. Yes, there was a tiny amount that made not difference to the symptoms after I put the bike back together. I think the problem is occuring as the bike comes off the idle jet and onto the main jet, but I don't know which thing to check next. I think it would be worth while to have the carb off and blown through by an airline, but I am not convinced that this will affect the running. I think it is the set up of the carb. Has anyone had similar problems or can anyone offer any advise on what to check / adjust? Any help would be much appreciated. Cheers Ben.