thanks for the replys they're much appreciated, i think the power loss occured in 4th gear around 7k- 8k rpm so today i took it to 9k rpm in 4th gear without any problems at all "smooth as ever"
so the problem whatever it is is intermittent. i service the ex-up twice a year, only did it last week, it was free & easy just as it should be. As for the the plugs
, i bought an AIS kit off justy & was going to replace plugs when i removed the AIS, just haven't got round to it yet, so ive had the bike 3 years come november so god knows how long those plugs have been in. i hope the above will help, obviously i need to get the plugs replaced, i'm off work for a couple of weeks i'll put it top of my "to do" list.......thanks Alan.