Two in the one day! So I've recently ditched the airbox for one of the foam filter intakes. Running jetting as per the recommendations most others are following: 168/170 mains 45 idles FactoryPro Needles, 3rd clip 4mm floats 1.25/1.5 IMS All stock air jets Once it's warm, it runs smooth, good and bloody strong everywhere. Idles fine, sarts when warm instantly. But even in 20 deg C weather, it struggles to start from 'cold' without the choke. Taking off on sudden throttle when cold, it hesitates coming off idle. Idling cold, if you give it sharp, sudden throttle, it falters briefly, and half the time it goes *coughclack!* and dies. More alarmingly, it's usually accompanied by smoke wafting out from the intakes, usually mostly the front one. Additionally, the hose at the bottom of the oil reservoir seems to pressurize and spurt oil out! :eek1 Put the choke on, or let it warm up, it stops happening. My theory was lean mixture detonating prematurely and causing kickback, but with 45 pilots it seems unlikely it would be lean. Adjusting IMS either way hasn't helped. Valves are in spec, carb boots are seated properly. Can anyone suggest what's causing this backfire/carb smoke?