KZ750 K1 - Low Beam Burnout

Low beam has burned out twice. It's a 10 minute, 10 dollar fix, but the thing is, I need my low beam - all the time...

Happened after I put a new voltage regulator on it, and I thought the fuse would blow before the light, but it burns out the turn signals too.

THis is only after 150 miles riding after having it a year - I had the top end rebuilt and it has a new wiring harness, battery, other odds and ends too.

Also, when It's hot, it has trouble starting, but starts cold no problem (as long as it's choked)

I've been waiting a year to ride the hell out of this thing, and I plan on taking it on 300+ mile trips, but when I can't get a decent 2 hour ride of it, it pisses me right off.

The low beam doesn't blow right away. When I put the new bulb in today, I strobed the shit out of it from low to high seeing if it was when the switch was activated (the electrical controls on the handlebars are all aftermarket and new as well, and my mechanic put those on)

I really don't want to take it back to my mechanic for this, but I will be having him put a new belt on it as well as reubild the brakes, but I'm tapped out on money for this.


I can ride it, but either with no light or a high beam and I'm on probation until december and I'm trying to ride as squeaky clean as I can (except when I make it go as fast as it possibly can, lol)

ANything helps

Ride safe

Use a multimeter or voltmeter to check how much voltage is being pushed from the regulator to the battery. This is very easy to check, just disconnect the headlight connector and hook the meter to the + and - battery terminals and run the engine. If the meter shows about 14.5 volts at 4000 rpm the voltage regulator is working properly. It shouldn't hit or exceed 15 volts; if it does the regulator isn't doing its job. Ed

Have you checked the battery voltage at 4000 rpm's? It should not go above 14.5 Volts D.C. I'd check all of the grounds(Black with Yellow stripe) for corrosion and tightness. Do you think the bulb is blowing out from vibration or over voltage? It's usually one or the other. If in doubt on the grounds, take a M6 X 1 tap, and remove any paint or corrosion from any place the grounds are bolted to the frame.

MFolks wrote: Have you checked the battery voltage at 4000 rpm's? It should not go above 14.5 Volts D.C. I'd check all of the grounds(Black with Yellow stripe) for corrosion and tightness. Do you think the bulb is blowing out from vibration or over voltage? It's usually one or the other. If in doubt on the grounds, take a M6 X 1 tap, and remove any paint or corrosion from any place the grounds are bolted to the frame.

Well, I know the one turn bulb straight up broke inside the casing, so I attribute that to vibration, so that might be the case with both the bulbs, but the headlight? It vibrates, and I didn't jump any train tracks, so that shouldn't be the problem, but I'll double check.

The ground for one of the front turn signals (the one with the broken bulb) broke, so I have to solder that back, so I'm just going to take the butt splices off the regulator and solder them, then put dielectric grease on the mounting bolts.

The ground for the regulator shouldn't be a problem, because I had to buy 1 1/2" M6x1.0 bolts last night after I put it on (the stock ones weren't long enough)

After that I'll hook the multimeter up to it and run it at 4k RPMs and see if it spikes past 14.5.

If it does I'll have to get real nasty with the ebay seller I bought the aftermarket regulator from - but my mechanic specifically told me to put a new regulator on it - and to be honest, after I did, it seemed all the electrical systems were much more responsive (mainly the time from I activate the turn signal, to the time it responds.

Sounds like I know where to go, but before we leave it at that and wait for me to check back in, I hook the multimeter to the battery or to the +/- parts of the headlight assembly? Both?

Thanks for all your help guys, you guys are the best, that's why I come here.

Ride safe.

Take the multimeter, and set it for Volts, Direct Current(VDC), range of 20.Put the RED probe on the Positive(+) battery terminal, and the BLACK probe on either the Negative(-) battery terminal, or a good frame ground. Start the engine up, let it get warm, and then take it to 4000 rpm, watching the multimeter. I find a set of alligator clips that fit the multmeter's probes to work the best for testing by yourself.

Salder69 wrote: Low beam has burned out twice. It's a 10 minute, 10 dollar fix, but the thing is, I need my low beam - all the time...

Happened after I put a new voltage regulator on it, and I thought the fuse would blow before the light, but it burns out the turn signals too.

The voltage reg is probably not regulating. As stated above, Rev the engine to 3V and measure the battery voltage: it should be 14V, if it's higher than 14.5V your reg is not working and that's frying your bulbs.

Multimeter set at 20V range DC had nothing go above 13.56V with the current voltage regulator on it.

I took off the new regulator and got the original and I'm putting insulated disconnect terminals (the flat kind, not bullet) on each, so I can hook the connector in and try/test both.

Choked her and started her and she started right up, so the warm starting issue is really beyond me, but I can kickstart it fairly easy after she's been running a good 30 minutes, so I'll use the electric starter for cold starts and then the kick for warm.

Should I post a new thread with results or just reply again?

Salder69 wrote: ...............Should I post a new thread with results or just reply again?

I suggest you keep this thread going rather than starting a new one. That way if in the future someone with a similar problem finds this thread using the "search" feature they will be able to follow the whole thing to its conclusion and apply the same repair. Thanks, Ed

The regulator does not ground through the case, it has a separate ground wire.
If the ground wire is not connected, the alternator will not charge and you'll run the battery flat. So that's probably not your problem

steell wrote: The regulator does not ground through the case, it has a separate ground wire.
If the ground wire is not connected, the alternator will not charge and you'll run the battery flat. So that's probably not your problem

Hey there. I appreciate your input, but I got confused by your post.

Are you saying the ground wire (which I believe is brown on the regulator) MUST be attached to charge the battery?

The aftermarket regulator does NOT have a brown wire, and when I asked my mechanic, he said that one shouldn't matter and it should ground through the frame.

All I know is I just got done soldering flat terminal disconnects on both the new and original regulator and the female ends on the plug that goes to the wiring harness.

I tested the new one last night and it didn't go above 13.56V (was about 12.6V at idle).

I'm going back to the unit tonight and going to test both, and after a good 10 minutes warming up this time, not the 3-4 I gave it last night, and rev the shit out of it and see it goes past 14V.

All things considered, I'll probably just put the stock regulator back on it and try and return the aftermarket one.

I want to ride, not deal with technical problems. That's what the winter is for...


Thanks for everyone's help.

Ride safe.