bike problem

[Dave Daniels]

I've been conferring with Dave Beard but thought I'd seek other opinions as well. My bike started running rough a couple weeks ago on my way home from work. Actually, it started right when I started it to come home. Sounded like it was running on three cylinders.
   
  Pulled the tank off and the spark plug wires off and gazed down the wells. No. 3 had oil in it, so I figured one of my figure 8 gaskets went bad. 
   
  So, I orderd some new ones and switched them out. Also put in new plugs. Got it all back together and started it up. It ran fine for a bit then started getting rough again.
   
  So, I pulled the plugs again and looked in the wells again. No oil this time, but no. 4 plug was getting carboned up.
   
  So, I cleaned them off, put them back in, put the tank back on and hit it again. Ran good for about a minute, then went rough again. So, I got a can of wd-40 and sprayed it on the exhaust pipes coming out of the head. It smoke completely off all but no. 4. It just ran down that pipe. 
   
  So, it seems no. 4 isn't firing.  Any ideas?
   
  Thanks,
  Dave D.