Another Stutterer

[red98]

Spent a bit more time on the bike today. Ran it for nearly five miles with no issues. Whilst it was ok tried putting the choke on to see if it made any difference. It didn't. Tried going down to 3000 revs several times and every time it picked up ok. Got to about 5 miles and she started to play up. Pulling any more than 1/4 throttle resulted in severe stuttering. Tried putting on the choke whilst the stuttering was happening, didn't make any difference. Road her home.
Replaced fuel filter and a friend lent me a set of vacuum gauges to check the carb balance. Had to adjust 3 & 4 ever so slightly. Bike was now getting hot and fan was running as expected. Blipping the throttle when the bike is hot results in a little stutter as you flick the throttle.
After the balance I thought I would remove No's 1 & 4 Diaphragms. They look and feel fine. The rubber is soft and supple and no signs of holes. I also removed the plugs and apart from being very slightly black they were fine.
After I had put everything back to together the bike had cooled down a bit. I started her up and blipped the throttle without any real sign of the stutter. Got to be heat/time related.
I'm now leaning more to an ignition or some kind of electrical fault. If it was a carb/jets/diaphragm issue then surely it would occur from the start.
What effect would a pick up sensor breaking down/overheating have?
Have a short couple of video's I took on my Iphone of the carb balance but don't know how to load them.

hi soapy......agree with you about the electrics  ,those diaphrams look fine,worth checking as you can now cross off you list of "possible stuttering causes"......iam just about to replace the pick up coil on mine,should be done this weekend as it looks like iam not working now (bl**dy weather)...will let you know how it go`s.......did check mine with a multimetre a while ago now and it checked out fine,this was checked with engine off ,not sure if you can check with engine running and at stuttering speed ......will have a think about that.