It probably would be lean if you uncorked the exhaust system with a freer flowing system. I don't doubt it is lean period. My point was it being lean is not why there is so much heat in the back of these machines. It is because they use a exhaust system with air injection and a catalytic converter as part of the emission system and they are going to make heat trying to burn off raw fuel the engine is emitting.
Not really even saying the engine is lean or rich but the pipe is glowing because air is being introduced into a fuel rich exhaust stream and making the temperature spike because that is what it was designed to do cook off fuel because the cat is not capable of burning that much fuel out of the exhaust. So you take away the air and dump more fuel the cat will be taxed heavily. If your going to do that IMO the cat should also be removed for several reasons.
It is unlikely that if you remove air injection and add fuel for it not have detrimental effects on the cat.
Using a catalytic converter and taking away the air and adding more fuel also it would not be possible for the cat itself it run cooler. It is what it does burn off un burnt fuel and the more fuel it is burning off is always going to make it hotter. Not saying that the pipe not getting so hot couldn't still make overall temps under there lower I don't know but my point is
you are likely going to have problems at some point as it is not possible to take the air away from the design and load it with fuel without the possibility of catalytic meltdown.
Possible even the muffler housing not getting tremendously hotter because the core is no where near the external wall but the core of the cat is going to be considerably hotter.
Just saying if you are going to defeat the air injection and add fuel then it would be logical that the cat needs to go also. If you remove major design component from the emission system then the job should be completed by removing all parts of the system especially when those parts are part of what allow the others to function long term.