TOPIC:

Just a thought - is the fast idle screw (the one linked to the choke) somehow interfering when the bike heats up?

Try and back out (or tighten?) the screw so it's nowhere near engaging and see if that helps.

Just a thought here, cause it happened to me, the big wiring harness that goes down the frame was just rubbing on one of the rods for the carby, the upright ones where you balance the carbs, seems it was just enough to slow the return of the throttle (sometimes) so had to cable tie it up a bit better to clear the linkage, also made it a bit easier to get the carbs in and out, as I said just a comment, cheers Pete.

The big wiring harness is close but not in the way. Thanks.

I have played with the fast idle screw in and out and doesn't seem to affect it unless the fast idle is actually engaged. Thanks.

Are all the choke plungers going all the way in when you take off the choke, I had a bit of play in the lever shaft and mine wouldn't quiet shut off so she was running a tad rich till I fixed it.

They seem to be. I'm not running rich, I'm having the opposite happen. I'm getting lean as it warms up.

I've had lots of little problems over the years, trying to wrack my old grey cells to remember what they all were, I did have another problem with fuel starvation when the bike got hot, and in OZ it's usually hot , turned out to be a crappy fuel line, the heat from the motor made the pipe soft and she sort of kinked a bit internally and starved my carbs, a bit of better fuel line and a straighter connection line fixed that, although now I seem to be starving a bit when I give it a gut full and keep it there, think the replacement vacuum petcock isn't feeding enough, might have to invest in a Pingle.