I have just completed checking my valve clearances on my WR400. I live on a remote Island in Australia and have only just gotten back into bikes after about 10 years out of the scene. There is no one on the island to help with mechanical troubleshooting so I have had to teach myself. I have learnt heaps off all of you guru's on TT. After checking my valve clearances I thought I should strip down my carby & give it a birthday. I had never noticed a bog in my throttle before going thru my carby but there is certainly one there now. Also my machine was no where near as responsive when I had finished with it. I have stripped & re-stripped my carby & cannot find anything in there that seems to be out of place. I ordered a jetting kit from Jd Jetting, ( excellent service) & I have put it in today & I beleive I am now close to sorting out my problems. I am in a hot environment 35deg celcius & up to 90% humidity. We are on a flat island, (less than 1000ft alt.) These are my bikes current specs. 2000 model WR400 WHITE BROS PRO MEG PIPE - 8 PLATES JD'S RED NEEDLE - CLIP POSITION 6 FROM TOP 170 MAIN JET IDLE MIXTURE SCREW 2.5 TURNS OUT PILOT AIR JET 75 PILOT JET 38 BYPASS VALVE SEAT 3.8 STARTER JET 65 MAIN AIR JET 200 I have stepped down from the 2nd clip position all the way to the 6th & my plug electrode is still grey. I do not know alot about jetting (obviously) but I feel that the 38 pilot jet should be more like a 45 maybe. The further down the needle my clip moves the more responsive it is through out the range. I haven't read of anyone running on their 6th clip position before, should I swith to the blue needle??? The other thing I am not sure of is whether my air mix screw is set correctly. I started at 1.5 turns out and kept unscrewing until the bike started to die then did the same screwing back in. I counted the turns & put it back at the half way point between the two deed spots, I ended up at 2.5 turns out. The last point is that I re-set my accel. pump screw as per yamaha's spec for my model which is put a 6.6mm drill under the slide & adjusted the play out of the linkage. I still have a noticable bog. I have read numerous threads on the different mods for ap problems & throttle bog & will try them if it gets to that but I cant understand why I didn't have it before I pulled apart the carby & I do now. The only other thing I can think of that may have some bearing on my problems is that when I check my spark it is not a fat blue spark, in fact it looks a little weak. I have done all of the electrical test in my manual & everything is in spec. The bike still does go very strong but I wonder weather it could be better??? I have already learnt so much off everyone on these forums but I thought if I gave you guys some specifics to my problems I may be able to get some more specific answers.