LED's use much less power, which throws off the blinker devices used in older bikes. This usually refers to the signal bulbs, not the indicator/dash lights, though it could have the same effect. The solution is to install "load balancers", which draw the current the LED's do not, throwing out any power savings gained by the use of LED's...
If you install LED's, you will need to use high-output LED's, with series-limiting resistors. Otherwise, look for direct replacement LED's, which are designed to replace specific bulb types. These replacements are plug-in replacements, ready to go. These do not have load balancing circuits in them. Buy one, and try it to see if it affects the blinker circuit -- electrical parts usually cannot be returned for a refund, only exchanged.
LED's burn for 50,000-100,000 hours, where filament bulbs last 1,000-12,000 hours. They burn milli-watts of power, where filament bulbs burn 2.5 Watts (dash bulbs), to 27 Watts (turn signal bulbs). They are worth converting, if no load balancers are needed. They are the last bulbs you will install. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII