Possible fuelling (CB125)

[Fairies attack]

The CB is being a pain in the arse right now.

It is struggling to get past 8k, everytime it hits it. The bike just seems to burble and pop, even down hill, and opening it up more makes it even worse.

If I come up to a corner and drop it a gear then, go to come on to the power (bit of a joke but hey) it seems to die, and feel flooded.

If I go up to 9k in 4th (I think) then take it to 60mph and change up it instantly bogs and drops back to 40mph. Riding in 4th (Whatever the gear from top is) it goes happily to 10k doing 60mph.

Not sure what the problem is, to me it sounds completely fuelling, since it dies then picks up, and looses power at certain revs. If I whack it back in 1st and keep going it will make 70mph, but the moment I stick it in top it just bogs and feels like it is going to die.

This is also coupled with the throttle sticking open, even though the cable is free and was oiled a few weeks ago.

Any ideas?

I did run it out a few weeks ago, but the tank fuel filter was cleaned from all the horrible brown gunk, so what else could be the problem?

FYI:
Engine rebuilt completely 2k ago,
New Rockers 500mile,
New filter and oil change 100mile,
Tappets done 500mile with rockers.

[Teflon-Mike]

sounds very like 'The Corporal' pre top end rebuild.
You say its been rebuilt.... how? with what?
Has it had a rebore / new barel?
Were the valves reground? (as opposed to 'lapped)
Was the cam timed in correctly?
Those eliminated, post rebuild, similar symptoms remained, but much less promounced.
Perished carb rubbers, were a bug bear, followed by worn needles & Main jets.
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[SpannerMonkey]

Sounds like my pc50, and thats due to igntition issues =) might be worth a thought.
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