Starting to gel with it now Rab thanks mate. Just fitted a pcv as need to sort fueling since fitting exhaust and removing cat. Bike pops on a closed throttle below 4k. Not sure the pcv will sort this though as its on a closed throttle so zero fuel. I reckon its the kleen (pairs in Honda speak) feeding air into the exhaust and helping ignite any unburnt fuel but need to do some.more research.