you could attach the cdi wire to another known good spark plug and then spin the engine at the speed its intended to go (with a drill or something) to see if their is a spark coming across the plug, if their is then the coil is producing electricity and the cdi (or cdi and ignition coil if their separate) are working properly, so its getting a spark. you could then take off the air filter, and spray starter fluid into the carb, and if it starts for a second then stops or starts firing at all then you know that the carb isnt giving gas properly. in which case it could be something as simple as the petcock valve being off or the fuel line (or petcock valve or gas tank opening or fuel jet) being clogged or partially clogged. the petcock valve that came with mine was problematic. i would start the bike and ride it, then after a bit it would start running lean, then stall out. or the carb is either clogged or not adjusted properly, you say you installed a new carb, which kind of carb? is it a dellorto, cns, or nt? from what i understand, the NT do work right out of the box most of the time, whereas the cns requires tinkering to get it functioning many times, and the dellorto needs the proper jet size (this i know from experience, the stock jet i had worked for me but was too lean, i had to order more jets.) if you dont want to order a fuel petcock, you can probably get a hose barb adapter from home depot or something that fits the fuel tank. just bring the petcock valve in and say you need a hose barb adapter with that size threads on the other side, then use an inline fuel valve if the carb leaks. i did that until i got a petcock valve. (you might want to drill the hose barb adapter to make it wider to get better fuel flow, i did, just clean the metal shavings well afterward so they dont mess up the carb or cylinder.) there could also be loss of compression. im yet to have that issue, but i believe their is a tool for measuring the cylinder's compression, unfortunately im not sure what it is, as ive never needed it, but maybe someone else knows what it is and how it works.
