***WARNING LONG POST***
Right guys, time for an update. There has been some nice weather here recently, so I gave myself a break from studying for my uni exams and decided to tinker a bit. Thanks for all your help, I think I may have fixed the problem (for the time being at least).
@LSM, that was the first thing I checked to be honest. I did the prescribed 'self tapping screw and silicone sealant' job on it, so just checked to make sure it still is fitted properly, and it didn't appear to be leaking or anything. I also replaced the rubber intake manifold as suggested by pretty much everyone at the service too so that ruled out that link.
@geoffbaker, throttle was fine too - was a bit paranoid about that one since I'm still not pro. at removing/refitting carb and throttle bodies - esp with the tank in place! But it dis indeed clunk, and I observed it through the air intake side as I turned the bars and made sure that the throttle body did not lift at all.
@Thumper, it was definately popping (so lean midrange? but see my findings below, they may contradict this, so maybe it wasn't a 'pop' as you describe it)! Infact when I was on my way home that last time I passed a few cyclists (the pedal kind) and damn near killed them cause i had a backfire right beside one of them. I put my hand up to apologise, but I felt like a right twit!
With regard to jetting, thanks to all who pitched in, here are my findings.
Before service, jets were stock and needle clip was in 2nd from bottom position. Got quite a few problems with misfiring before I did the service, and low and behold the plug was covered in soot when I took it out. So I kinda knew my bike wasn't gona like big jets just quite yet (waiting for new exhaust for that!)
First off (after service), the carb was fitted with 120main and needle clip in middle. About 30miles after service (it was a fresh plug at service) this was plug colour;
Brown, but looking quite dark. Anyway, after I started having all the problems I described earlier, I had to use a bit more of the throttle to get around since it wasn't liking the midrange. After my last trip just before I posted on here, with the same settings as before, but with about 50 more miles on it, started to look a lot more black
I stuck a new plug in and decided to drop the main jet to a 117.5 ( i thought the 120 was maybe causing the whole mixture to become rich and fouling the plug with more miles) but richen the needle up (1 clip down). I know I should have probably done them one at a time, but basically this was my decided treatment and I was sticking to it! Anyway, after going for a nice 50 mile jaunt yesterday (where I was using all of the rev range, but mainly cruising at 50-60mph). Had a wee peek at the plug after some midrange riding and this was the result (very good light cause it was so sunny!)
That looks like a nice chocolate brown/cafe au lait colour there. Would you all agree, or do you think it's too light and I should richen up a bit more? It's a bit more difficult to start now, got to give it a bit of throttle, but seems spot on after it's warmed up. My only concern is that even though it's a bit more difficult to start, it still refuses to start at all with the choke on! I though that this indicates a rich runner, but i've always had that problem even from bog stock day1...
Anyway, thanks again for your help!
Cheers, Stu