Glowing Muffler Headers Okay (Solved)

[Ilikemotorcycles]

I've worked on bikes and engines for years but I can't get the GS500 to run right.
2007 GS500f with only 1800 miles.

Before the carb rebuild the float needle center pin was stuck in the the needle  essentially making the floats set higher. This was making the engine flood very quickly. Wet plugs.

I've rebuilt the carbs, set float height(13mm)and checked that I have the little O ring under the diaphragm cover. I didn't replace diaphragms because they seem good and I left the carbs together because the fuel inlet T wasn't leaking. Fuel mixture screw set at 2.5

So the bike seemed to run fine so my next step was to go through the warm up procedure mentioned here and get the air mixture set and the idle where is should be. Starting on choke it would go to 3-4K like everyone says it should. After a minute I ride off through the neighborhood.

I'd say after about 7-10 minutes I loop back by the house to check on everything. I'm getting some backfireing. Not a load crack like sometimes when you shut an engine off and start back immediately but just a consistently louder exhaust note than at cold start up. I can see the inside of the muffler is red-orange hot! But the headers are still black.

From what I understand the PAIR system routes clean air into the exhaust to finish burning any fuel.
The plugs are black so I'm guessing it's rich and making the muffler a second combustion chamber.
I can ride it long enough to get it "fully warm" to start adjusting the carbs before the muffler starts cooking

I haven't checked the ignition timing or the valves but I wouldn't suspect that because of the low miles and if the valves or timing was making the exhaust red hot the headers would be red too?
What could be making it run like this?

[grader]

you said it was running rich before you worked on it, maybe the exhaust is now fuel soaked and is just burning off. also you are still rich if the plugs are black. take it for a good long ride and check it when you get back, the exhaust should clean out and you can recheck plugs.

[Ilikemotorcycles]

I replaced the plugs and it ran much better until it got hot. The inside of the muffler still got orange red hot but took longer. I think one of the plugs were bad so it was running one cylinder and burning all that fuel from one side in the muffler.
Since it ran really well and on both cylinders until it got hot I think a coil might be bad and weaken as it gets hot. I'm going to try running it once it cools down and see if that helps. Has anyone had a bad coil kill a spark plug?

[user11235813]

I replaced the plugs and it ran much better until it got hot. The inside of the muffler still got orange red hot but took longer. I think one of the plugs were bad so it was running one cylinder and burning all that fuel from one side in the muffler.
Since it ran really well and on both cylinders until it got hot I think a coil might be bad and weaken as it gets hot. I'm going to try running it once it cools down and see if that helps. Has anyone had a bad coil kill a spark plug?

Easy enough to test the coil with with a multimeter.

[herennow]

Coils are well known to have symptoms that start only when hot. This is quite common.  you can test this by swapping coils around and seeing if problem moves to other side of engine.
you can tell if bike is runnign on one side by checkign temperature of each side (by hand - dangerous, by cheap 20$ infra red thermometer - safe) or by pulling cap off spark plug and seeing if bike runs.  should run - badly - on each cylinder alone. DONT DO THIS FOR LONG - JUST A FEW SECONDS - IT CAN STRAIN YOUR COILS.

Does seem you are running too rich. Maybe check fuel height with clear tube - you could maybe be getting leakage past the needle valve outside seat (bad o-ring)

Good luck

[Ilikemotorcycles]

Thanks for the replies! I finally figured it out. But before I found the issue I did check the float height and I swapped the coils to the opposite cylinders. Neither attempts changed anything. So I decided to go over the carbs one more time and found the pilot jets were ruined by the previous owner. I just wasn't paying close enough attention to catch it and I would usually only look through one jet at a time. Some drilled out the pilot jets to different sizes.
If you want to see how bad it was i made a video.
Here's the link : https://youtu.be/42KDHFQR0bs