Caddy - The writeup.

Thought I'd whack it here for you to read at your convenience rather than waiting 'til you're online or trying to explain it over the phone.

Started him up - Popping, backfiring at first. Settles after a min.

Pulling away/riding in low gears - underpowered, stalls occasionally. intermittently clearing causing sudden increase in power (I nearly back-ended someone as I was leaving the rugby club due to this... ) also popping and backfiring.

Motorway speeds - He actually seems quite happy at high speeds.

Verdict - Don't go slow.

D'oh!.....poor Roger

That could have said "FAO Caddy...". I'm quite relieved that didn't say what I thought it was gonna...

Sound like a blocked jet in the carbs to me, I had the same earlier this year, its rather similar to carb icing in its symptoms. Though the sudden increase in power and the fact its fine as high speeds says blocked/fowled jets to me.

I quick test would be some Redex in the tank, though if you can pop the tank up and fire him up with the airbox off you should be able to see the jets squirting, or not squirting as the case maybe.

Sounds like a blocked pilot jet to me. Easy to clear if you pull the offending carb off the bike and strip the float bowl off it. You can blow the jets clean with either carb cleaner, or an aerosol can of compresssed air. The pilot jet usually sits alongside the main jet, set up into the body of the carb. It's a little brass thing with a slot screw head that has a tiny hole in the centre. The main jet sits in the centre of the carb body and usually protrudes downwards into the float bowl. It's a bigger version of the pilot jet and normally looks like a long 6 or 7mm nut with a hole drilled down it.

Easiest way to find out which carb is playing up is to check the heat from the downpipes when you start it from not quite cold. Start it up on choke and run it up for a minute or two then turn it off. Leave it to cool down then come back and start it again without choke, and check which downpipe is getting hot. The cooler one has the blocked pilot jet in the carb.

G'day all! Finally got back online, but don't have a phone line in my new place yet.

Ping! It does sound a bit like a jet issue, and the fact that he's running well at high revs rules out an air leak in the system (i.e. air box coming off).
It's blummin strange though as we've had the carbs apart and cleaned everything in them including the jets. It could be a tuning issue (which is out of my league), but it could be a bit of residual detritus in the system. At least you can tonk the hell out of him!!! And he does run a lot better now the air box is on

Anyone else got any ideas? And where's Spannerman when I need/deserve some abuse!

Might be a bit of crap has worked its way into the jet, and as said before I would blow it out with carb clear first and see how it responds.