weak battery? hard to start and run

[spf]

My '89 GS runs like a top until last Thursday. Previous owner and I have kept up with maint. Motor always comes to life immediately, before I can take my thumb off the button. Here's the prob. - riding to work, switched to reserve and rode 4 more miles, arrived at 7am. At 4pm, no start.  Had I goofed and turned the switch past lock and left the rear taillight on, draining the battery all day? Started charging the battery, went and picked up 2 gallons of premium.  30 minutes later, refueled, very hard to start. Could get maybe 4,000 rpm, not much more. Could hold steady in 3rd gear, but would bog down when I gave throttle. Left plug was sooty. Pulled both plugs and checked spark which was blue but seemed wimpy. Installed new stock NGK plugs, same result. Doesn't idle well, even when I adjusted main screw. Hauled my baby home and need to get it running. Haven't had a chance for battery test as of yet.  Can't suspect carbs, since they have been running fantastic. Appreciate your advice. — spf

[craigs449]

My guess would be that you sucked up some crud from the bottom of the tank when you switched to reserve and you have a partial blockage in the carbs.  I would try a bit of seafoam, then pull the carbs for a good cleaning after rinsing the tank a few times with fresh fuel.  It doesnt take much to clog the jets, especially with crud that has been sitting near the bottom of the tank since 1989!

[spf]

Thanks - that Seafoam cures everything from cancer to ingrown toenails. Never used it on any of my bikes.  Will give that a try, then clean the carbs, etc.  Appreciate the tip!