Warm/Hot starting issue

[LAB3]

Well I'm pretty well stumped at what's been going on with my bike, it's been taking 10-15 seconds worth of cranking to get it started after only about 30 minutes of riding. Cold starts are just fine, no need for the choke as long as the temps are above 55° or so. I've been through all my electrical connections more than twice but have yet to touch the carbs, it runs just fine once it gets started. I've read that an old and worn out starter relay could be the issue but have put off replacing parts without a good reason to suspect something is afoul. Any ideas as to what I should be looking for or at?

[DiverRay]

If you don't need the choke for a cold start, you are running rich. Try full throttle when you crank, and see if it starts quicker. Just open to full, and then hit the starter button.
You may want to think about putting 1/2 can of Berryman's B12 Chemtool into the fuel tank before your next 30 minute ride. This will help break up and clean out any buildup from ethanol laced fuel.
I'm lucky in that I can buy ethanol free gasoline here in Idaho. That is ALL I run in the bike, and my small engines.

[Radioguylogs]

Checked the air cleaner recently?

I know I only look at mine about every 5 years and they are fine, but I don't put the miles on any one bike like you do.

I have the same intuition as DiverRay since it starts without choke -> seem rich. If it starts with the butterfly open, it will confirm rich.

[skids]

Mine will sometimes do it when hot if I eat lunch or something. If I pull the "choke lever" all the way out and use the throttle when cranking it starts. It is not intuitive because cold use of the choke requires no throttle.

[LAB3]

Checked the air cleaner recently?

.

Got around to cleaning my air filter on Sunday (Uni) and it indeed was quite filthy. Generally speaking I clean it at every oil change and I think I must have used too much oil on it last time I cleaned it. Made a run of about 100 miles yesterday with a few stops and it started back up as it should.

As to not needing to choke most of my bikes have never needed it in the summer months. It got chilly this weekend and it certainly has needed it the last few mornings.

[gtem]

Mine will sometimes do it when hot if I eat lunch or something. If I pull the "choke lever" all the way out and use the throttle when cranking it starts. It is not intuitive because cold use of the choke requires no throttle.

Skids I've got more or less the same thing with my '79. I've always heard hard starting when hot/warm can be associated with too-tight of valves, but I just recently adjusted mine, on the loose side of the spec. I just chalk it up to the nuances of a 45+ year old machine.

[DEEBS11]

Yes, when the valve does not sit firmly on the seat, compression leaks out and makes it more difficult to start. Why worse warm than when it's cold? - The heat expansion makes it even worse and it loses even more compression than when it's cold with minimal or no valve lash gap.