The white smoke indicates the need for new valve guide seals. The black smoke indicates that the fuel/air mix is far too rich. Re-jet the carb to stock #137 main jet. Don't mess with the pilot jet if the bike idles okay. No other settings to mess with. Install a new stock plug ; NGK R CR9E
ALWAYS have a fire extinguisher on hand when working on carburetors.
Drain the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Spray into all the little airways and fittings in the carb. Check the jet needle clip on the top of the needle. Put it in mid-range. Put the carb back together, clean the air filter and install the carb. Let the float bowl fill then start the engine.
I just thought of somthing. You may be creating the rich mix problem yourself. See the following starting instructions.
There is a proper way to start the engine. Four controls are on your bike to assist in starting.
Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Now release the de-compression lever. Give the throttle a 1/4 turn then let it snap closed. A diaphragm in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. Now give a strong kick through the full sweep of the kick start lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from the kick lever. This happens in the case of a misfire, aka > backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), until the bike starts. A good battery, a clean spark plug, a clean carb and clean air filter will also aid in starting.
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