The plug is a welch plug. The JB will get you going but welding is the answer in the off season. I doubt that would cause your current issues though. I would pull the plugs and ground the wires. Then crank it with it with a towel over the holes. If it pumps out a bunch of oil, then keep cranking in short bursts until you just get a mist coming out. Then put the plugs in a let er rip tater chip... Hopefully you will be good to go. But if not, there are several members in your area that may be able to help. [MENTION=52309]MPower[/MENTION], [MENTION=59515]suke[/MENTION] [MENTION=72134]1983[/MENTION] [MENTION=32110]IDoSeaDoo[/MENTION] all are really smart guys. Maybe you can drag it over to one of their places and I am sure they would look at it. I am out of town the next two weekends or I would offer to help. Good luck and hang in there.
That is typically leaking needle and seats. That is what is was in all the ones I have seen do that.
It floods the engine then when you try to start it it mixes with the water trapped in the muffler and you get the sludge in your picture.
Rebuild carbs with factory Mikuni kits and needle and seats, replace fuel filter and selector and gray fuel lines then should be good to go.
I got spare carbs but they need to be gone through I think. If you just park it for a couple of weeks I will help you out. I wish one of the Raleigh guys would pop in. I hate it that it is giving you fits. I am not worried about the gunk in the exhaust. When it starts once good, it will blow that crud out. So it started for a few seconds. What was the idle? Or did you just struggle keeping it alive by blipping the throttle? When it dies, are the plugs wet? Have you verified your plumbing? You can simplify it all by running one line from the tank to the carb, bypassing the selector and filter. Then put the return line in a empty bottle or something. Once it starts, you should have fuel returning. If not, something is not plumbed correctly or is clogged. Did it only start once or several times, at a few seconds at a pop?