Only other thought is its something electrical breaking down as the engine warms up? But you seem to have changed those bits.
RWB XRV 750
Red XRV 750
Yellow Honda Trail 90 - CT90 no 1
Red Honda Trail 90 - CT90
Red Honda Trail 110 - CT110 Special
Yellow Honda Trail 90 - CT90 no 2
Horses for courses
Sounds like fuel starvation but you seem to have covered all the fuel stuff, . . . However this unleaded fuel can leave a gungy deposit in the carb (specially if the fuel tap was left on) and can reduce the effective size of the jet's. ie the brown deposit coats the jets inside, thus reducing the bore.
did you remove the jets to clean them ?
As you i thought it must have been fuel problem but im really beginning to think its something else, im gutted i cant get it going and i dont want to send it oo an expensive mechanic when im sure if i can get an idea what the problem is ill rectify it.
presumably it has been running OK at sometime, revs and power through the whole range?
How's the air filter?
-=[1998 XRV750 RD07A]=-
Did you have the plug cap checked? You havn't said if you've tried some of the suggestions.
Double check float height. Had a similar effect on a Guzzi once. Turned out to be a loose float needle seat, but again, if the float height is wrong, you'd get the same problem.
Why timing? Have you touched it?
Tried a new plug? - breaking down under load.
But, if bike was okay before, the fact that it was left for a while, have you checked all connections for corrosion?
Off road in Portugal; Cracking Grommet
First biking experience - dirt biking in the desert
First Honda CB200 in 1978
Biggest Honda CB750F2 in 1981
Lots in between
Some bikes have thrombosis; there's a clot behind the bars!