97 carb. Up until a week ago this bike ran like a Swiss clock. Went out one eve and it ran fine. Half way home stopped at a junction. Pulled away again and the surging started............From stone cold it's perfect....After approx 4 miles the bike starts to surge on a partial throttle. Say 2500rpm and up. At wot it pulls like a train. Until its warmed up the bike is like silk but the hesitancy / surge appears to be getting worse the hotter it gets. Albeit it never cuts out it feels as tho someone's pulling on the grab rail slightly. It idles perfect at about 11 - 1150rpm. So far, Carbs balanced, Tank cleaned and fresh fuel, New fuel filter, New petcock diaghram, New fuel supply lines and vac pipe. All vac ports have their plugs in No leaks at carb inlet rubbers (tested) Carbs stripped completely and cleaned. Stock carbs. No bent needles or wear. All diaghrams are perfect. Jets are whistle clean. Factory setting on air screws. Carbs are stock factory to UK settings. Floats all good and in spec, no wear marks. New air filter, Air dams in place in front of air filter intakes both sides. Plugs are new and iridiums, not fouled. Ht leads are 5k ohms on the caps and contacts are clean. Coils are 2.9 and 3 ohms at primary windings and 33k at secondary. Continuity from cdi to coil leads. Continuity from ignition pulse sender to cdi. Ht leads are also in spec, 5v present at tps. All header pipes equal. With bike running on idle if I pull any cap there's a noticeable change in engine noise ie cylinder out. This is driving me crackers. To the point I've had enough with it unless someone can shed fresh light please?Thanks!