i use one of those bicycle mirrors that plugs into the end of the handlebar tube. The metal tube is thicker than on a bicycle and the plastic mirror mount had to be trimmed a little to get it in the hole..
It will go faster if you change that muffler with just about any free-flowing exhaust pipe.. it will get loud but it will likely go about 5 to 8 mph faster with no other modifications.
There's no easy way to clean a carburetor. Stalling and flooding might be a float adjustment. Might be bad fuel flow.. might be vacuum leaks around the manifold.. I would take the time to pull the carb and find the problem and fix it.
The easiest way to get to the carb is to remove that large pivot bolt in the front of the engine. The engine will drop to the floor. Now remove the four intake manifold screws and remove the carb. First, disconnect all nearby cables and wires and lines that are routed through the engine area.. Decompression cable, throttle cable, rear brake cable, fuel line, condenser wire, sparkplug wire, etc..
Have a buddy hold the bike while you remove the bolt and lower the engine.. slowly. Watch carefully for any wires, lines or cables that you forgot to disconnect.
When you put the engine back up, do it before reconnecting any cables. Then re-route the cables and wires so they don't have to be disconnected the next time you lower that engine.