Back fire at startup

No they have a special arrester to stop that from happening, it is required by law.

have you tried checking the lean,rich needle on the carb sounds like it's to lean. good luck

Does the cooling fan ever run when the engine is hot? If not, you may have a problem with the fan thermostat.

For the record, spray carburetor cleaner does no good if it's sprayed on the outside of the carburetor with the engine running. That's not what it's for.

Noises are very hard to locate on engines. You may have a valve lifter that bleeds down when the engine isn't running. Not a major problem but let the engine warm up before revving. It's probably more trouble than it's worth to replace it.

the reason that the catylitic converter is hot is because of a rich condition in the engine, one cylinder is not firing. This is most likely the cause of the back fire that you are having. It may be related to the tapping sound if it is a valve that is bend or broken.

Turn engine until valve tappets are on the back of the cam lobes. (TDC firing) Adjust as per any engine inlet .010" hot and exhaust .012" hot. Turn over until next piston in firing order comes to tdc (90 Degrees) and repeat process of adjustment.

Clean throttle body

If it is running that hot, I have a strong hunch that the engine is running way too lean.

Do NOT ride it on only one cylinder. Lots of bad things can happen. Sounds like some kind of electrical problem with the one cylinder. Could be bad plug or plug wire or a loose connection or intermittent short/damaged wire at or near the coil.

yes, provided there is no excessive build up. The gas and air mix must be right before the mixture will ignit. a household stove will do this each time it's turned on. That's why yhe igniter sparkk hits about three times before it lights. proper venting will confine any fumes to the cimbustion chamber to be carried out the exhaust. If the odor is strong then have the appliance checked for safety sake.