bigger headlight bulb

is it true that the kz900 altinator cant handle more wattage than an h4 bulb.what are the options?will a police alternator fit?anyone try THE SYLVANIA brite bulbs (silver or something like that)or these XENON GAS ,or LP USA ION bulbs?
Lockhart Phillips eCatalog

Post edited by: mark1122, at: 2007/08/15 10:24

Post edited by: N0NB, at: 2007/08/15 15:35

I don't have an answer, but
here's a way to post the link
without skewing the page so
much:

THE LINK

EDIT: Nevermind, the link has been fixed above. Thanks, all!



Post edited by: Biquetoast, at: 2007/08/18 08:39

OK, you're asking the wrong question. See, an H4 bulb is available in a variety of "strengths". Fer instance, on my bench I have three H4s. One is what is usually thought of as standard, 60 watt high beam filament, 55 watt low beam filament. The other two are 100w/55w and 100w/80w. The wattage refers to how much heat/light they produce (actually it's a number that represents work, but these are light bulbs, so...) and it is directly related to how much current each one draws. So, a 60w/55w bulb draws almost as much current on low as it does on high, so your electrical system really doesn't care if you have your headlight on low or hig, it needs about the same electricity. However, if you were to use a 100w/55w bulb, when you had your brights on your electrical system would need to make almost double the current for the heatlight system. This isn't a problem for your electrical system as long as you are turning at least, say, 3500 rpm. So, your system could use a 100w/55w H4 bulb, as long as you were careful not to use the brights while idling for awhile before shutting down. Now, if you went to a 100w/80w bulb, your headlights would always want a bunch of electrons, even on low, and you might not have the alternator for that.
Clear as mud, no?

I believe the H4 for motorcycles is 35/55.
It also has heavier guage supports for the
nichrome wire to handle the extra vibration
and bumps that a motorcycle bulb has to
endure.You can try a stronger bulb,but check
your fuse for excessive heat.

Actually, I think you might be right about the 35/55 bulb. But I've never had a problem with an automotive bulb on my 4 cylinder. Yeah, if you're running a big twin without balancers, or have a rock-hard suspension like my cafe racer in the 70's, a vibration-resistant bulb might be necessary. But my 1100 never seemed to eat bulbs. However, if you do run a bulb of significant wattage, and use 30 year old switches, you might want to use a relay. A Bosch-type 87/87a works. Just wire the low beam on the 87a blade so that if you have a switch failure your default is low beam. With my 100/80 I'm going to wire in an extra relay and resistors like this to give me a Daylight Running Light without an ongoing 80 watt drain on the system:
(ah, heck. Photobucket's not uploading, so I'll post it by attaching.)

wow .thats over my head???ok lets say i start with the simple meathod u first mentioned.a 55/100. what simptoms am i going to look for if its drawing too much power? wouldnt i just blow a fuse? i have a 1974 wireing system with just 1 20amp fuse for the whole bike.are u running this relay and 80/100 on an old z1?

Mark,
It shouldn't blow a fuse. Years ago I ran a 55w/100w offroad bulb in a Marchal headlamp on my KZ650C1 without a problem (other than the bulb itself eventually burning out). It was very bright at night on high beam. The issue is that if you spend lots of time idling at low RPM with the high beam on, like sitting at traffic lights in city traffic, your electrical system may not put out enough power to keep the battery charged up. Assuming that your electrical system is working up to spec, if you keep the low beam on when idling or stop-and go driving you should be ok. Ed

I run a PIAA "super white" H4 bulb in my KZ900. It's rated at 85w/85w. I have had no problems with my charging syst or wiring while running this bulb. I will note however that I keep my battery in good shape and have made sure that my wiring connections at the harness are clean and make good contacts.This bulb is bright! Just ask R4 :whistle:

pstrbrc.let us know how that works out.i think i could do that.it does sound like i could get away with an 80/100 though if i keep the revs up ,right? i never ride below 4000 rpm anyways and that would put out 14 volts but how many watts do these thing make??