Motorcycle Repair: 85 honda shadow 500, electrical, header pipes, combustion chamber

Question
hello,  i'm trying to troubleshoot a 1985 honda shadow 500 (vt500).  i've owned the bike from new and never had any previous issues, and have never made any modifications.  i believe the fault may be electrical.   several months ago while riding through rain the engine dramatically lost power, it still ran, and quickly recovered, this happened several times.  just recently it has happened again, although not recovered this time.  the engine will start, although not easily, it will not idle without being given some throttle, the engine sounds different, the bike can be ridden but with greatly reduced power, the tach guage reads 0, i did check for spark by removing one of the two plugs for each cyclinder while the engine was running and spark was observed at both.  

any ideas?

thanking you in advance.

Answer
when running the bike check the heat of both header pipes... is one cold ? if one of them is cold You might have a bad plug cap, you could have water in the carbs and a fouled plug.... A sparking plug, out in the atmosphere only means that there is some spark. The plug has to fire under thousands of pound of pressure inside the combustion chamber.... plug cap, new plugs, drain the carbs too, put it back together-try it... yes-good, no- remove the tank and seat and go through the wiring connectors and clean all of them. try it now...