it's impossible to picture what kinda overall condition the bike is in.. the exhaust is so stuffed up you are trying to start with it diconnected, so the condition is probably bad.
Are the head bolts loose also, and so you have about zero compression? Is the exhaust port on the cylinder blocked with carbon?
Fuel, compression and a spark are required to start and run.
Spray some Starter Fluid into the airfilter or carb. If you do have compression and spark, the bike will run for a moment. Now you know for sure all you need is fuel.
Where exactly is the fuel flow problem? Perhaps it's a dirty carb but you may be out of gas for all i know.. Or maybe the choke is not operating. (Starting requires a very rich mixture. Without a choke, this might not be able to happen.)
If bolts and nuts are loose .. if cables are not adjusted properly.. if .. well.. there's a lot of ifs besides 'if the carb is dirty" that can cause no-start.
Keep in touch.