Motorcycle Repair: restarting after storage, suzuki bandit, valve seals

Question
Hello Mr. Howell,
I have a Suzuki Bandit 400cc, 1991, 4 stroke. I had the carborator synced three years back, replaced the plugs at that time as well. The next year after winter, I tried to restart it and couldn't. Had a mechanic look at it and said the plugs were dirty and replaced them. Ran well. This year, same old same old. The bike won't start. I took the plugs out and it was covered with black carbon looking stuff. It wasn't chunky, just coated in black. I brushed off as much as that stuff as I could. Still won't start. I'll be replacing the plugs to see if that'll work again this year.

Question 1: Do you think that the plugs would be the only thing keeping it from running? I know that is hard to answer being that you haven't seen the bike.

Question 2: What is causeing the black stuff on my plugs? And how do I remeedy that?

Thanks, S. chiu

Answer
S, The new plugs will make it run, The black stuff on the plugs in oil residue most likly from worn valve guides,Sometimes the valve seals get hard and cause the black also.I would first run a compression test,Then a leak down test to make sure the rings are ok.If they are ok you will have to take apart and check the guides and seals.Good luck. Try me again. Glen
P.S also check the carb. jetting ??