There is a significant voltage drop in both the "hot" side and the ground circuit of the KLR headlight wiring, about like almost every other bike on the road. Some exceptions such as bigger Hondas.
It's simple to determine this, just put a voltmeter lead on the battery positive and the other lead onto the headlight high beam terminal with engine running and light on high beam. The voltage which you read will be the difference (lost voltage) between the battery and the high beam. If memory serves a Gen1 KLR is about 2 volts lost. I think the ground circuit is 3/4 to one volt from memory. The drops are certainly substantial.
My first KLR with headlight relays, had a headlight which was as bright with engine not running (about 12 volts across the battery), as stock Gen1's with engine running (about 14.5 volts across the battery). With engine running, the 2-1/2 volts greater to the headlight made a very significant improvement. It was almost like the bike had a headlight.
Time has moved on so I no longer do headlight relays. For years, I installed 35 watt HID which were about like a relayed 100 Watt Super Silver quartz bulb. The HID draws about 2.4 amps, while the stock 60 watt QI bulb draws about 4.6 amps with relays. The 100 watt draws around 6-1/2 amps with relays. Since the HID kits come with their own relay and dedicated power lead, plus they draw 4 amps less, which is huge on a KLR, the choice is a no-brainer, IME.
Before someone goes on about the light shell not being designed, blah, blah, I've installed something over 30 of them in KLR and no one complained about being flashed by other drivers. If it's a problem, the cost of an HID kit is something like $20.00 off eBay so not a big deal to try.
For a year+, I have been installing an LED H4 bulb off Banggood, which have been on eBay for a while now.
These draw about 2.8 amps and don't seem to be affected noticeably by voltage drop on a KLR so, other than to upgrade the fuse holders (a no brainer, IMO), all which is needed is the bulb.
These compare to two 100 watt Super Silver QI H4 bulbs in a Honda ST1100 with wiring upgrades. In other words: like 200 watt headlight.
The difference between the HID and the LED is about like a stock headlight with engine not running to a relayed KLR with engine running. I strongly recommend trying the LED.
This is the LED:
http://www.ebay.com/itm/112233171127?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The HID are like this:
http://www.ebay.com/itm/Motorcycle-HID-Headlight-Bi-Xenon-AC-Slim-Ballast-Kit-H4-H6-6000K-35W-Hi-Lo-Bulb-/171434316061?hash=item27ea48111d:g:5boAAOSw7ThUdD98&vxp=mtr
A few more points, in case they are useful to someone, I strongly recommend:
1) Replacing the KLR fuse holders (both generations) with weatherproof inline ATC or Mini fuse. They are available off eBay for a couple of dollars each. Much of the electrical problems I see on KLR is from bad fuse holders/connections.
2) The White Wire (Main Fuse Holder to VRR, Fan, Ignition Switch, is too small, so I run a second white wire up and terminate it to the cooling fan relay which gets rid of most of the voltage drop.
3) The headlight and common ground wiring is both too small, too long a dog's breakfast of back and forth + junctions. A good remedy is to pop the ground terminal connector out of the headlight plug, solder a 14 gauge wire across the top of the terminal, then put the terminal back into the plug. Ground the other end of the new wire to one of the 6mm bolts (10 mm head) on the overflow tank frame.
4) The voltage drop from the VRR to the White Wire is excessive and can be improved. If someone wants to know about that, or the VRR mod, post back.
These topics come up frequently on KLR Technical if that's of interest to someone on Facebook.
HIH
Norm