. My Euro WR400 has a #165 main, 42 pilot and a DRQ needle, 4th from top. Stock exhaust which oddly says “Not for Road Use” despite being quite quiet. Anyway, same as my WR450 from a few years back the stock jetting is very lean at low throttle and makes the bike run stuttery and snatchy, Popped in a #170 and much much better, but then do some digging and find lots of stuff from Mr Dean about using a needle with more taper to increase mid-range: http://www.thumpertalk.com/topic/45025-yz426-jetting-boosts-yzwr400-midrange-power/page__st__20 and for some reason I can’t even recall I happen to have an EMN brass needle in me box of bits! This needle has a steeper taper (first letter D vs E) and thinner straight part (last letter “N” vs Q), but the differences are quite small without comparing with a micrometer. Put it in the bike (+165 main) and holy- sh** what a difference! The pick-up from low revs is verging on the astonishing for a mere 400 - I would never have believed a WR400 could have so much grunt! And the power just builds in one long arm-pulling surge to max revs, wow. All very good, and the bike runs much smoother at low revs, real civilised. HOWEVER, the extra richness at low throttle has resulted in a slightly wooly pick-up from idle using only a small tweak of the throttle, like say blipping the throttle when down-changing at low speeds. Crack the throttle more and the pick-up is instant, no bog, its just when you ride very gently its noticeable or say when trickling along at idle in 1st. Still got the #42 pilot in, and fuel screw about 1 ½ turns out, but adjusting has no effect on my wooly problem. Funny enough I had a very similar problem with the WR450 when I richened up the low-end, though as that had more power it was not so problematic. Any ideas? Smaller pilot perhaps?