I was going to reference someone to one of the DIY's about installing resistors (one of the easier options after replacing stock incandescent bulbs with LED ones) just now and noticed there WASN'T a specific DIY about it. There are DIY's for installing aftermarket flashers, but none on tossing resistors in the circuit. It gets brought up a LOT and people say, "Just install resistors" and I know I've tossed a couple of pictures and drawn up some quick diagrams on how to wire them before, but there's no specific threads on it.
So here goes.
I explained briefly how thermal flashers work in one of my factoids
and how replacing your high wattage incandescent bulbs with LED ones significantly drops the load in your turn signal circuit. Unlike with most car turn signal circuits the bulbs in most motorcycle turn signal circuits at wired in parallel. This means that when one bulb is gone or replaced with an LED the wattage draw drops so the thermal element inside the flasher doesn't heat up. If the thermal flasher doesn't heat up then it can't cycle. What happens is you turn on your turn signal and they light up, but they stay lit because the thermal flasher never disconnects the circuit to cool down.
So what? So installing resistors "mimicks" the missing bulb(s) and allows a predetermined amount of current TO pass through as it would if you retained your stock incandescent bulbs. If the flasher was meant to operate in an environment with a 50 watt load (two 25-watt bulbs) and you replace the two bulbs with a 50 watt resistor the flasher won't know (or care).
Wiring-wise you just splice a resistor into each circuit (one for the left turn signal and one for the right turn signal). Each resistor typically has one red wire and one black wire. Most Kawi's have a black wire with a yellow stripe (your ground wire) and a green wire going to the left turn signal and a black/yellow wire and a gray wire going to the right turn signal. Often times you can access the wires pretty easily from under the passenger seat (and often there's plenty of space under there to mount the resistors as well).
On the left turn signal circuit find the 2-wires (they'll be next to one another) and splice the black resistor wire to the black/yellow wire and the red wire to the green wire. On the right turn signal splice the red resistor wire to the gray wire. The absolute easiest way to do this (although not the BEST way, but it works) is with a wire splice:
If you're not technically saavy this will work and last probably as long as you own the bike. The preferred way would be to solder the wires together and cover with shrink wrap to prevent corrosion though.
Wire splices allow you to slide it over an existing wire, slide the wire to be spliced in, and when you clamp it with pliers a metal piece cuts into both wires thus joining them.
As for the resistor part you can find the load resistors at most any auto parts stores and they sell them like crazy on eBay. They look like this generally:
depending on the size you're using. This particular one has black leads coming out of both side so you just wire one of the black leads to a positive side in the respective circuit. The direction of electrical flow doesn't matter for these resistors.
The resistors can get hot (as the product of wasting current is heat) so I would suggest not mounting them directly to plastic. I cut a small piece of sheet aluminum to mount mine to separate them from the plastic.
Here I mounted my resistors to a simple sheet-aluminum plate, bent it so it sits over my CDI and riveted it to the plastic piece it sits against. Easy peazy.
Resistor sizing depends on the load you're trying to replace. Since each turn signal bulb is typically 27 watts if you're only replacing one bulb per circuit you only need to splice in one 25 watt resistor per circuit:
If you're replacing your front AND rear turn signals then you are replacing a 50 watt load (per circuit) and the resistor required will be double the size:
Quick side note: There are only TWO turn signal circuits on a vehicle. You can mount the resistors anywhere on the bike and splice in near the front turn signals, the rear turn signals, next to the flasher, etc. So the front left turn signal and the rear left turn signal are literally the same circuit. Hence the wire colors to the front turn signals will match the wire colors going to the rear turn signals.
So yeah if you splice in a resistor into each turn signal circuit after replacing your bulbs with LED's you should fix your turn signal blink issues. That's it!