Ok thanks. Im taking the bike apart as far as i knowledgeably can, im not going to take the carbs off because ive had problems in the past with getting them back on. Ive only just noticed, my chain is very tight, ive loosened it now, could that have caused any drop in power?

No- you can stress the chain and the output bearings..but I reckon the motor would still win.

ah damn.. ok i was hoping it was something as easy at that. The breather hose from the air filter into a box on top of the rear two cylinders, what is the box for? i havnt got a small enough spanner to undo the screws to see what it looks like inside

That's the crankcase vent.

Aye, no need to look in it - you'll see the camshafts. it allows the engine to breathe into the airbox as the gubbins is all whirling about inside the cases.

thats ok then, glad i didnt go any further. Im still really confused with it not getting the power. theres nothing blocking the air, the vacuum is fine, fuel is getting into the engine fine (ran the bike without fuel connected until it died, put the tank on, started fine), when i try to hold the revs at say, 4000 it jumps all over the place, it mostly bogs down between 5000 and 7000 rpm. Swapping the spark plugs around doesnt change anything.
I also put some shell performance in the tank (or whatever its called, the better stuff) to see if that would make a difference, it doesnt feel as though it has.

took it out about an hour ago, seemed to be a bit smoother but still drags, also doesnt seem to want to rev 9k+. It will, just feels as though it isnt getting enough fuel to keep it revving.

And the plot thickens. My carbs dont have a pilot screw. My Haynes manual says i should have one, but ive taken the carbs off, inspected them as thoroughly as i can, and definitely no pilot screw.

I dont know if this has happened recently or further back in the past or if its somehow come loose, come off the carbs and given me this problem, as i havnt purposely taken the carbs out to look at the pilot screw before, so ive never noticed. Ive googled as much as i can but there isnt much to tell me if theres any way someone can service this bike in such a way that it will run fine with no pilot screw setting..

If anyone has any thoughts, let me know ASAP as im using the bike every day and i dont want to damage it, if not any further. Thanks!

I'm amazed it runs at all well enough to ride without some pilot screws. In all carbs?

You got a pic? Sure it is they that are missing?

As i havnt had to deal with pilot screws before, im 99% sure that i am looking in the right place according to my manual. I will get a picture when i get a chance to take the carbs out again