Cylinder stops firing when bike heats up

[metalfab]

Set up a test spark plug with an extremely large gap. See what the max gap each coil will jump with the engine cold. A failing coil normally cant pass this test. The bad coil should have weaker spark, and the color will be different too. Also check the voltage to each coil when it dies, you could be loosing power. If its new enough to have electronic ignition, one of the drivers in the ignition box could be failing when hot.

[Rijko]

Set up a test spark plug with an extremely large gap.

I know, i am a bit of a nerd :-)
Love the old Suzuki Service bulletins.
Like this one : they warn to not let the gap exceed 8 mm or you may blow the coil. (page 5)
Guess they mean extended testing as they describe removing the side electrode altogether on page 3.

[earlfor]

Carbs seem OK, according to previous posts.
I did not see this issue though:

Each coil fires two cylinders and you have a problem with only one misfiring.

Small break in wires could be culprit as the break would close when cold, and open more when hot and even a weak spark combined with compression could still fire at higher RPMs

Change the plug wires and connector.

It's a 450. Coils fire one cylinder.

[epytus]

All the electrics talk got me on the right track - it's fixed! But for a pretty shameful reason...

The battery was bad. Yeah that's it.

I originally thought this wasn't going to be the case because I tried with the battery on the bike and separately with a car battery jumper hooked up. The jumper is basically just a motorcycle battery in a case, actually the exact same internal battery I have in a scooter I own. So I figured it would have ruled out the battery issue. But nope.

I bought a new battery because I noticed this one wasn't taking a full charge anymore. Still could crank the bike up but apparently not good enough.

I'm guessing the battery was losing charge after a few minutes of running. Either that or the cables were coming loose on one of the nodes when it was heating up. Then the cold might've tightened it up again as it contracted. Therefore causing the 2-3 min working time and the working again after sitting for awhile.

Thanks to everyone who chipped in I appreciate the thought you guys put into it and I probably would still be stuck thinking it's my carb without this forum!