FZR 1990 35/35W -> 55/60W Bulbs

yesterday i took the day off and decided on a whim to go to the automotive store near my home. it happened they had relays and wiring (that kragen didn't) to do the headlight upgrade i had been only half considering. the 30A automotive relay was $22 and the harness was $10.

Mind you, i was pretty terrible in circuits when taking physics in school. the guy there at the shop that helped me was really into it and thought my project was pretty interesting. he and his boss helped come up with this diagram (which i modified the FZR wiring diagram to make finding wires simpler). i didnt have to buy extra wires since the harness had wires that were approx 7 inches long and were 14 gauge, much heavier than the stock ones that were .... really really light.

please excuse my misuse of terminology... but here's the basic gist of the upgrade. instead of channeling the current that powers the headlights from the harness through the headlight switch (which i heard burns out if you use a 55/60W bulb on the 35/35W wiring), i used the relay to accommodate the larger draw. the headlight switch instead of directly switching the power back and forth between the low and high beams would now switch the relay on and off. basically the relay is always on "high beams off / low beams on" position until the switch on your handlebar switches the relay to "high beams on / low beams off". but that would mean the power to the headlights would have to come from something that turns on with the key instead of being on all the time (even with the key taken out).

here's the schematic of what i'm doing.

when you flip the high/low beam switch, the plate inside the relay flips from 87A (low beam) to 87 (high beam). the power from the high/low beam switch... instead of powering the headlights themselves, now sends the signal to the relay. that way there is no overload on the hi/lo switch at all.

i tapped the switch power (main switch) to power the headlights since it's a heavier gauge wire. i think it's the same as the harness, 14 gauge.

i had to do some work figuring out which wire is what, but here's what i ended up with. i have the stock wiring and modified wiring attached. i erased the rest of the stuff on the diagram so it wont be as confusing.

it's funny that the right headlight is only high beams and the left is hi/lo, when both of them seem to be hooked up to be able to accomodate both hi/lo. maybe someone can answer that for me...

If you really want to get it right, use two relays and run power from the battery with an inline fuse on larger wire. The stock wiring was designed to carry the stock load.

two relays? one for each bulb or one for low's and one for high's?

yeah, a fuse would be a good idea! i'll put that in today

Looks fine to me. Good idea to not route the headlight power through the switch. A relay should always be used.

I presume that the stock system actually does route the headlight current through the switch and there are no relays? If true, the only reason I can think that they made it that way would be beause they only installed 35 watt bulbs. (What are they thinking?)

If, however, the stock system employs relays, you didn't need to do what you did. For instance, the stock wiring on my Honda ST1100 employs two relays. One for the low beams, one for the high beams.

Note: If you really want to get maximum performance out of your lights, bypass the stock wimpy wiring and run a larger gauge fused line from the positive terminal of the battery to the #30 on the relay. And upgrade the wiring on the ground side of the circut. And to avoid having the light on all the time (duh!), wire in another relay for that new fused line that would be switched on or triggered by the Switch power lead. You'd be surprised by the voltage drop seen in stock motorcycle wiring. And small voltage drops can have a big impact on light output.

haha... sounds good, but what does "voltage drop" mean?

dkcwenge said:

two relays? one for each bulb or one for low's and one for high's?

Click to expand...

Yes, use the three wire stock headlight wiring to power the relays. One position is low beam, one is high beam.

what should the fuse to the relay be rated at?

i just called the guy that helped me and he did a calculation that what i would need would be an inline 10 amp fuse. the wiring is also 14 gauge.

Actually, the simpler way is to use the two relays with one handling the chore of turning on the low beam and the other handling the chore of turning on the high beam. Run the output from your high low switch to these two relays. I.E. the wire that goes to the stock low beam filament would now go to the #85 of the new low beam relay. The wire from the high low switch that used to go to the high beam filament would now go to the #85 of the second new high beam relay. With the stock wiring, neither relay would be activated with the ignition off so you wouldn't need the relay in the power circuit for the headlights.

Then run that new lead from the battery (locate the new fuse as close as possible to the positive terminal) and go to the #30 terminal on both new relays. Then the output terminals #87 on each new relay would go to their respective low and high beam filiments. Finish it off with heavier gauge wire for the ground side of things.

By the way, if you're interested to see what the voltage is that your bulb is seeing, simply unplug the connector from the bulb and measure with a meter between the appropriate connectors for both high and low beam operation with the engine running at 3000 rpm or so.

Voltage drop is a result of the natural resistance of a conductor. For instance, if you've got 12.8 volts at the battery and are running a light bulb 3 feet away and the wiring is a piddling 18 gauge, the bulb doesn't see 12.8 volts. It sees less than that. Upsize the wiring and there's less resistance and the bulb sees more volts and is closer to full brightness.

I'll try to find some good links for you. Suffice to say that gernerally speaking the wiring on motorcycles is marginal and most often, if you upgrade the wiring going to and from your headlight, you'll end up with brighter, better performing headlights. Much closer to what the headlight and bulb manufacturers originally intended.

Read this link: http://www.danielsternlighting.com/tech/relays/relays.html

Also, check out the rest of his site. Lots of very good information on lighting and bulbs.

Here's a good calculator. Scroll towards the bottom of the page:

http://www.powerstream.com/Wire_Size.htm

And if you're looking for a fuse block, these guys make one of the very best around. Different sizes. With and without the negative buss.

http://bluesea.com/category/5/21/productline/126

Voltage drop is also dependent on voltage, which is why hi transmission lines are up to 100,000 volts.... power loss is minimal.

I used to do lots of low voltage landscape lighting, for all practical purposes, you tried to never run more than 20 feet of wire. Some of the jobs I did had remote underground transformers in a vault and had #8 wire needed to go 40 lousy feet to feed a couple of lights that could have been fed with much smaller wire were the run ten feet.

oh awesome! thanks!!

Bump for awesome info.