Eddie, I have read alot of previous xr400 jetting threads after searching but still have not solved my problems which I think may be jetting related. Bike: 2001 XR400 Conditions: Live at 6200 ft with low humidity in Wyoming. Ride mostly from 6200-8500 ft. Would like to get jetting right for 68 degrees Temp. (most riding from 50-90 degrees) Mods: XR's Only exhaust and header pipe, Snorkel Removed and previous owner drilled a bunch of holes in the top of the airbox which add a measured 18% area to the original opening (without the snorkel), UNI air filter with open filter frame (no screens). Current settings: Stock Keihin Carb, A16A Needle with clip in 2nd notch from top, 155 Main, 55 Pilot, Fuel Screw 1 1/2 turns out, Valves recently checked and adjusted with no noticable change in performance. Running Issues: 1) Very difficult to start when cold - starts first kick every time when warm. 2) Cuts out when you crack the throttle off idle whether I try it when in neutral or when I'm riding slowly in 2nd gear. 3) Gurgles/misses when running wide open. All testing has been done with warm engine after riding for awhile. I bought it 6 weeks ago from someone at a lower elevation and I changed the jets from 158/58 to 155/55 and it did improve some but still has the same symptoms, but now the air temp here is getting colder so I'm not sure how that is affecting things. Between the very top and bottom it has run very well on hard trail rides so I think the needle setting is good. When I had the 58 pilot in, turning the fuel screw did very little in affecting the idle rpms and it would still run with it turned all the way in. With the 55 pilot it seemed to idle faster at about 1 turn out. Do I still need to go leaner? Would that help the cold starting? I can live with the off idle cut-out and wide open gurgle because when riding it hard on trails I never seem to be at those extremes but I really want to get this thing to start easier when it's cold. Thanks for your time and any input you can give me.