Wet, oily plugs. Bike either doesn't start or only runs for 5 minutes before dying

Wet, oily plugs. Carb already set to leanest setting.

Bike either doesn't start or only runs for 5 minutes before dying.

Everything was great when I had the stock muffler on, that is until the endcap fell off. After that, it got very loud, stared backfiring like crazy, lost most its power, and kept flooding the plug. The situation has not changed since I installed a new $20 chrome muffler that I got from thatsdax.com.

Today I put a fresh plug in to test my new muffler and rode for about 2 minutes. I checked the plug and it was wet. I repeated this 3 more times and the plug keeps coming out oily and wet. Besides the wet plug, it is still backfiring every once in awhile.

My carburetor has its E-clip set on the top, leanest, groove, and I've turned the idle air screw out half a turn to make it leaner.

I have the CNS2 carb and I'm running about a 32:1 ratio.
Note that the plug was black and wet before this whole endcap thing happened, but it was still running very well for as long as I needed it to.

From the symptoms, I think it it's too rich, but my carb is set as lean as possible without getting a smaller jet. A secondary explanation could be that the ignition coil isn't firing correctly, but I don't know how to test it.

Like I said, it was running great before the endcap on the black stock muffler fell off.

Please help me troubleshoot.

Re: Wet, oily plugs. Bike either doesn't start or only runs for 5 minutes before dyin

Earlier today I checked for spark. The spark plug cap that came with the kit is really loose, and they gave me two of them. I would have preferred 1 good one instead of 2 crappy ones. Anyway, I wasn't quite getting a consistent spark, so I switched the cap out with the unused one and checked for spark by taking the plug out, grounding the outer electrode to the engine head, and rolling the bike forward for the engine to turn a few times. This time I got a consistent spark.

Tonight I went through the carb. It had some fuel in the overflow line, but the floats are adjusted OK I think. I reinstalled and turned the petcock to the on position without any further overflowing.

After that, I started her up. She goes for a while, but still eventually dies and when I pull the plug, it's still oily and wet. If I give it any throttle whatsoever, she dies immediately. If I let it idle, she goes for awhile (1-2 minutes).
Since I had the carb's throttle needle on the leanest position this whole time, I decided to move it's e-clip to the center position. This goes against all that makes sense, because my plug comes out wet, but I'm out of ideas. I'll try to run it again tomorrow.

Re: Wet, oily plugs. Bike either doesn't start or only runs for 5 minutes before dyin

OK, I checked for vacuum leaks by spraying carb cleaner onto the carb intake and also around the head gasket. The engine did not surge, therefore I ruled out air leaks.

After that, I checked the magneto. This may not come as a surprise, but it was not screwed in all the way, and the ground wire wasn't fastened securely.

The other tips either of you gave are probably not the cause, but thank you for the ideas. Chalk it up to my inexperience and crappy build quality by the manufacturer. I think my problem is solved. Now the bike is ready for my camping trip this weekend (after I tune the carb)!

If I somehow end up with the same problem, I'll update this thread.