First, a big thanks to JD, Clark, and Taffy for helping us to understand how to jet these bikes! I thought I would post my setup as it seems to work fantastic. Perhaps others can benefit from this too. There are A LOT! of new folks on the list that may want to listen. I'll preface this by saying I have tried quite a few settings before, my jet parts counter guy links I'm a loon. This has been a learning process for the last year. While other settings have given good results, the following has given the best so far in terms of sheer power that is still useable. Temp: 50 F Altitude: 800 ft Humidity: 48% (could be a little off, this was from a very old baromter) Terrain: mixture of mud, soft MX track, leaf filled trails, hills, no sand. Bike: '00 WR400. YZ timed. Stock YZ pipe. WB tapered Ti header. Airbox lid off/thottle stop cut, WB powerfilter. No other engine performance mods. Other stuff than may be of interest: Use castrol 20W/50 oil. Red Line watter wetter. OK, here's the beef: Jetting: Needle: EKP #4 Main: 170 (172 felt no different) Pilot Jet: 48 Fuel Screw-1.1 turns Main air jet: #100 All other jets/settings stock (AP and TPS stock) As a few folks have mentioned, a combo like this gives a nice torquey feel down low and is smooth on the trail. The moment you wick it past 1/4 thottle, it leaps to life. 4th gear wheelies (14/52 gearing) where doable for sure. Very smooth, yet on the verge of peaky power. Slamming the throttle open is not a problem, it doesn't bog at all! I was using the EKN for a while, and while it felt pretty darn good, it seemed to "overreact" a little too much. Wheelspin seemed to be more of an issue than the EKN. Since it's a typical slippery spring, I opted to continue to use a little smoother combo. Thre EKN (#4 was really the only position that worked well at all) also seemed to bog a bit when opening the throttle quickly from idle/off-idle. I hope this helps someone out with a '00 and similar setup. Please note, with WR timing this probably isn't the hot ticket. On a totally separate note: Under the advice a tire thread a few months back, I tried the Mich S12 front/D755 rear for soft-terrain conditions. The D755 works better than a 756! The S12 was AWESOME! The control and resistance to washing out was superb! I may keep experimenting with rears, but the S12 is a keeper!