Ok, when you clean your carb, remove all the jets, the needle jet, and the idle-circuit adjusting screw, and clean them all out real good, using spray carb cleaner, and make sure it blows out thru all the little orifices real strong. This includes all the little orifices and passages in the carb body as well as the jets. Pay close attention to that tiny little orifice in the carb venturi floor, just behind the needle jet, and make sure it's clear.
Even when it looks clean to they eye, it might not be. Blow it out good with the carb cleaner. Be careful. It can blow back into your face because it's powerful spray, and you don't want to get it in your eyes.
As the weather cools down, the bike needs to run richer than it did before. It might even require a jet change, depending on how it was previously jetted.
When you put it back together, put the idle-circuit adjusting screw at 1.5 turns out from the closed position. That's a good starting point, and then you can work it in by ear from there, if it needs to be. Turning the screw in richens, and turning it out leans. It's an air bleed screw. If the bike runs best with the screw turned pretty far in, then you probably need to go to the next richer pilot jet.
Make sure that there's no visible cracks in your rubber intake hose. They might not look like they go all the way thru, but they sometimes fool you and leak air anyway. Clamps need to be good and tight too. Also be sure you're not leaking air at the gasket between the intake manifold and the head.
The way I solved my exhaust leak at the head was to get a piece of aluminum roofing flashing(thin sheet metal) and wrapped it around the headpipe where it goes into the head. Just one wrap, so that the flashing butted-up against itself and didn't overlap. This was just the right amount to make a better fit, and stopped the exhaust leak. I then trimmed it to the size where it didn't stick out from the head, and you can't even tell it's in there. I was lucky and got the right result the first time. It may require some experimenting with different thicknesses of sheet aluminum to get it just right. But it does solve the problem without goopy gook on it or ceramic glue, or anything like that. It's a clean fix.
I was using a cold BR9ES plug over the summer, which worked good, but I switched to a hotter(normal) BR8ES for the colder winter months. That worked good.
Make sure that you aren't shedding any rust particles from the inside of the gas tank down into the carb. And periodically check the fuel bowl to see if there's any water collecting in there.
Also, I index my plug. I know some people think it's immaterial, but I think it helps.
In a hemi head like the Bullet, the open part of the plug ground strap should face into the chamber, biased slighty toward the intake valve, at about 1 o'clock position. You can make a mental note of where this aligns on the porcelain outside of the spark plug, and just screw it in so that it will be indexed correctly. Sometimes you need a fresh crush washer for the spark plug to get this right, but quite often it will line up without having to get another one. Don't over-torque the plug trying to get this right. If it doesn't line up pretty easily, then just leave it be, or get another crush washer.
This helps ensure that there is proper flame spread off the spark plug electrode for more reliabile ignition and better burn of the mixture, and some say it's good for a little extra power too.
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