Higher Wattage Headlight Bulb OK?

The MKII motors had the same high output alternators as the J motors had. That was one of the big changes.

Ok, I've read this topic post, and another one about switching out/adding lights and what the wattage issues would be.

I'm looking at doing this also for my bike: '82 Kz750, and after looking at the manual, it says it's a Sealed Beam 12v 50/35W headlight. My question is, what do those numbers mean, and would replacing it with a H4 55/60W (those are the most common ones I'm finding on websites) make any difference to power consumption/effectiveness of the light? I do not know what size headlight it is (ie. 5 3/4" or 7").

What this means is that your Lo beam is 50W and the Hi beam is 35W and it is a sealed beam meaning that the entire light has to be changed. If you go to a H-4 than you will have to buy a headlight reflector that is considered a Semi-Sealed beam meaning you can change the bulb in it. The H-4 bulb that you are looking at is 55W lo-beam and 60W Hi-beam. The power consumption on the lo-beam (which you will use 95% of the time)will be only a third of an Amp more than the one you have. This is insignificant. On the high beam it will be an additional third Amp. Once again insignificant. H-4 bulbs come in different Wattages. I have some that are 100/90W output. That will double the total power consumption of the electrical system and would cause a big problem. At that point the bulb would draw almost 8.5 amps instead of the original four point something.

Great info . So basically the 55/60 won't be an issue for power, that's good to know. Also, other posts suggest LED lights, or sticking with Halogens, but then suggest a certain reflective lens, or whatever the technical term is, for the headlight. Would that be a major concern, or do most sealed beams have the newest and brightest lens in them already?

Sealed beam Halogens work fine. I use Wagner. The H4 bulb type that goes into a reflector works well also and allows you to replace only the bulb when it burns out plus gives more choices. I ran one of these for years (Marchal) and tried several different bulbs including a 100W one. That one did push the electrical system to it's limit, but it sure was bright at night! I went back to sealed beam because the reflector eventually got a bit dull and flakey inside (maybe from the heat of the 100W bulb?) Ed

Another thought is if you use a higher output alternator stator to run 100 Watt bulbs, the plastic headlight housing and related wiring may become "Crispy Critters".

cperrotta wrote:

Great info . So basically the 55/60 won't be an issue for power, that's good to know. Also, other posts suggest LED lights, or sticking with Halogens, but then suggest a certain reflective lens, or whatever the technical term is, for the headlight. Would that be a major concern, or do most sealed beams have the newest and brightest lens in them already?

I believe the standard 35/55W units are for LOW beam and hi beam respectively. The low beam is the 35W lamp, so going up 20W to 55W will be about 1.4A increase which is not a whole lot.

In rating automotive bulbs xx/yyW the first #xx/** is always the Hi-beam the second #**/yyW is always the Lo-beam. Hayla has a very good explication of effect of different power outputs on your system.
www.rallylights.com/hella/BulbHelp.aspx#LightOutput

Thanks everyone for the knowledge and info! Much appreciated.

So just to complete my story, I ended up getting a 55W/40W (up from a 50/35). Slight weirdness at first, but it's running ok now.

Side-effects:

- I have a much brighter light now. Luxurious, after the old one. It's Halogen.

- At first, the right blinker Indicator was stuck half-on (dull glow). Now, that one works fine but the left indicator is shot, doesn't work. I've been meaning to check the fuses, but if one's working and the other isn't, I can't imagine it's fuse-related.

Don't even know yet if you can replace the bulbs in that dash unit. My guess would be you have to replace the entire unit as a whole. We shall see.

If anyone has any good recommendations on new coils or anything to make the electrical system a little more strong, resilient, etc. I'm happy to hear about it.

New sparkplug caps, new sparkplug wires(or high tension leads known to some riders)and new coils would be where I'd go along with a fresh set of properly gapped sparkplugs would be a good "tune up".

mind2find wrote:

So just to complete my story, I ended up getting a 55W/40W (up from a 50/35).

- I have a much brighter light now. Luxurious, after the old one. It's Halogen.

I think that's what everybody runs now in the 7" round lights. I think mine is about 3X as bright as the stock lamp. Once when my halogen popped, I put the stock one back in temporarily. I rode off at night and turned around and came home because it seemed like I was blind in the dark.:laugh: