78 KZ650 D1

I started a thread about this a while back but haven't been able to work on things for a while. I figured I'd start a new thread because so much has changed since the first post.

My main 20A fuse blows as soon as my bike warms up. I fire up the bike and without touching it at all, the fuse will eventually go after about 2 minutes. If I replace the fuse immediately after that and try to start the bike again, the fuse will blow instantly. Sometimes it blows as soon as I turn the ignition key but this is only after the bike has warmed up.

Due to scorch marks and excessive heat (will burn your fingertips) around the connections to the reg/rec, I thought maybe I had a bad reg/rec. A couple people told me to unplug the reg/rec and see if the fuse still goes. So I did that, the fuse still went.

This leads me to believe there is a grounding problem elsewhere, though, I have searched high and low on this thing without any luck. I've opened up the controls and headlamp almost a dozen times, no exaggeration, and can't see anything.

Is there anyway to use a meter to track down something like this? I feel like I'm just shooting in the dark here.

You have to isolate circuit branches. For example, warm it up and shut it off. Then remove the red wire that feeds the coil and turn the key on. If it still blows, It's not the coil. Disconnect the headlight, etc. Try to find something that when disconnected, keeps the fuse alive.

What it can be is wires in the harness that got stretched rubbed through the insulation and can ground out. Those are pretty common

Incase you need.... KZ650 web site dedicated to 650's....
Wiring Diagrams...

http://diagrams.kz650.info/wiring/WiringDiagrams.htm

2 thoughts come to mind in your situation,,,, but first, to blow open a fuse whether heat, electron flow all that theorhetical down to earth scientific theory of applied science, keep it simple... Excessive current through that fuse blows the fusible link....

With that said.... in your case may be explainable but screw that....

If blowing open after 2 minutes, you're most likely drawing close to the 20 amp range right off the bat... After a couple minutes it just gets so damn hot it blows the link open.....

Or..... after a couple of minute warm up period, something on the load side of the fuse (non regulator side) takes a direct dump to ground....

As can be downloaded from the provided site for your KZ model, if that drawing is correct, the regulator could crap directly to ground and that fuse wouldn't give a rats ass for that is a direct feed into the battery (+) ....

Try this.... Disconnect everything for bare bone minimum operations....

Stater/Dynnamo, Vdc Regulator connected as designed, feed the +12Vdc into a inline 20 amp fuse then a 20 amp on/off single pole/single throw switch... The switch out put is your feed into the coils RED/Yellow conductors....

If you have a Dyna ignition, also switch +12Vdc to it...
Even disconnect the starter and use the kick start... INsure your feed back for charging the battery is connected but d-connect everything else.....

Now run your test... fuse blow yes/no....

If no, then one at a time start plugging in your other connections... Example, start with d-connecting everything but what you just had in a bypass off the ignition switch...

Otherwords, battery to 20amp fuse to white conductor up to ignition switch... Jumper switch outout to coils only... Test... Blows Yes/No...

Then re-connect lights or brake stop light what ever... Basically one at a time... until you find the one connection that blows the fuse... chances are it;s in the instrument cluster/head lights....

I realize this is somewhat confusing so I'll STFU now....

As a side question, is it normal for the two yellow wires coming from the alternator to the reg/rec to be super hot? And if so, could they be getting hot as a result of anything other than the alternator?

Confusing??? Naw. I know what u were trying to say and I read it and it made perfect sense to me--but of course I'm in the rubber room at the old farts home right now so everything makes sense to me,including this little cocka rocha Ive been talking to for the last few minutes.Beeba-bubba-booba-bumble.bj

In all seriousness,get some spray electrical cleaner and clean the fuse contacs on the fuse block as well as the wiring contacts that attach to the fuse block.They do get corroded.bj

I'll mention that I have swapped out my fuse box for mini ATO blade type fuses.

Good point BJ... One better, replace them old fuse clips with these....

BTW "Beeba-bubba-booba-bumble."... Spewed my Dr Pepper...

Yeah I'm rocking those already. Good stuff.

You have a DVM capable of DC amperage measurements?
May provide some answers....

Yeah my meter can do Amps DC for sure.

Can you elaborate on what I should do with that. I'm pretty new at this stuff.

Measure on a cold start your current draw...

~8-9amps or are you pulling ~ 18-20amps right off the bat.....

If at the latter, turn off the engine immidiately and start disconnecting one at a time your electrical harness connections until you find it drop ~ 9amps....

See if your on the extreme high side right away, would explain why your Stator wires are hottter then normal....
Meaning your over taxing the AC generation due to a short/faulty....

That sounds interesting. I'll try that.

Newbie question: What connections do I need to make with my meter leads for the Amps DC test?

Did this all start to happen after you put the new style fuse panel in?
The connections on your meter? Most will have a separate 10 AMP hole to put the red positive probe into, then the black negative stays in the same hole. Turn the Dial to DC 10 AMP setting, then 1 lead goes to one side of the fuse, and the other lead to the other side of the fuse. IF you get a negative reading swap the lead around to change polarity. Your meter more than likely will be able to take 10 AMPs, but there is a fuse inside that will blow if you exceed this much, maybe 15 AMPs. There is another way to test for a short to ground, cheap, but may take awhile.
Get a spare 12v bulb with 2 test wires coming off of it, put it across the battery terminals and it should light up. This verifies the light works, now hook 1 end of the light to the hot 12v side of your main fuse in series, this means still using the fuse for protection, and the other end to the load side of the circuit. First without turning on the key, do a full, and I mean full wiggle test of the harness to see if it shorts. The light will come on/ blink if it gets a ground. You may need to have the tank/ side covers/ head light bucket/ seat open to access this. If it doesn't light up, then it would be on a circuit which is switched. Then back to unplugging and trying to see if there is 1 Item you can pin down. They do sell a short circuit finder, there is a meter that can be run along the harness, and a circuit breaker with a buzzer that takes the place of the fuse.This buzzes when the short happens.
As far as the 2 yellow wires getting super hot, no this should be a minimal amount of heat. the heat is from resistance in the connector, and more than likely the wiring that's close to the plug. You may have to clean the connector, but more than likely the wires are damaged and you would need to either cut back to good wire and splice, or replace the wire completely.

alexnelson wrote:
They should not be super hot. One thing to always remember on old bikes: hot wires and hot fuses don't always mean excess current, it can be corroded connections. The associated voltage drop across a corroded or dirty connection creates a ton of power dissipation.

The alternator wires may be getting hot from too much current, or conducting heat being generated in the regulator/rectifier assembly.

alexnelson wrote:
Unless you have a meter that can measure >30A, don't try it. You'll blow traces in the meter.

Good point Bounty
Keep in mind.... Most DVM meters are designed with internal fuse ratings of 20Amps for AC/DC current measurements.....

NOTE I said most so as Bounty mentioned, read your DVM manual no doubt....

Same time, his situation is not blowing the fuse right away so most likely not a dead short thus >20amp current flow....

To answer your question... With meter set for DCamp measurement, 20 amp range or higher.....
Your DVM manual should inform you of exact DC amperage configurations but useally conifigured as such.....

Oh god, here we go.... Electron flow is negative to positive.... Engineers are taught the oppossite...
I look at this way, as long as it is flowing to spec I'm good....

* (+) to fuse leg.
* Otherside of fuse to Black DVM probe.
* Red probe to switch/ignition switch....

What's your measurement?

BTW, have plenty of 20 amp blade fuses ready.... It will take a couple blown fuses to figure out....

One of 2 ways to go about it...
1) Start as mentioned with bare minimum connected for running....

2) Start as is presently connected & d-connect one at a time...

OMR

Motor Head wrote:


No. The new fuse panel was one of my many attempts to fix the problem.

It all started when I opened my headlamp to tighten the nut holding the left signal light to the headlamp housing. Now you're all thinking, "Well, your problem must be in there!" Maybe it is. But like I say, I've had then thing open so many darn times and can't see anything wrong.

I took my tac and speedo off a while ago. I rode for at least a couple weeks with them off before this happened though.

My point is I've been all over the bike and I can't see the problem with my own eyes so a method of testing is all I have to go on.

bountyhunter wrote:


This is my meter.
ca.fluke.com/Fluke/caen/Digital-Multimet...-77-IV.htm?PID=56126

mA-10A

Guess I can't do the Amps DC test.

Huh...?

First page of your link....
10 Amps continuous (20A for 30 seconds)

Same time, nice meter you have there so get yourself a clamp type current meter then you won;t have to worry about it....

Or better yet, they do have Fluke Current Clamp adapters that plug and play (measure) for the fluke DVM line of products.... Spendy, well yeah but it is a Fluke after all and you want to fix your baby right...

Something caught my eye in your last postings....
Disconnect the headlight harness plug and re-test....
Fuse blowing?