Topic: 1976 cb550k blows 15amp fuse when engine kill switch is turned to run

[wizzy]

Hey Everyone

    My name is Jason Wisniewski and i recently bought a 1976 cb500k. It did not have carbs with the bike when i bought it, and since then i am in the middle of transforming it to a cafe style bike.  It is all bone stock except for the clubman bars i installed. i was moments away from trying to start the bike for the first time in a while. I bought the bike from it's origional owner sice 1977. the bike has been parked since 1982 from what he told me.  i had to unplug all hand contols to take off the old bars and reinstall the the cafe one's.  i anm knot sure about the wiring in the headlight i just matched up all colors that were the same.  now when i turn the ignition key to run, the oil light and nutrel indicator comes on, horn works headlight dosn't and it is new not burned out? and when i move the engine kill switch from off to run it blows the 15amp fuse instantly. like is said before it is bone stock wiring.  if any one out there has any suggestions please help.
Tank you in advance Wizzy!

[dusterdude]

cant help much,but its obvious you have some kind of short in your wiring for the kill switch.i would remove the switch block from the handlebars and try it and see what happens,if it works that way,you are probably shorting when you mount the block back to the handlebars.good luck.

[wizzy]

Will the bike start with the kill switch controles disconnected?

[jrtruckn]

If I remember correctly the starter switch is on the same button panel as the kill switch. Atleast it is on my 74 550. Could be in your starter switch? If you can disconnect the starter switch then try it. I would try removing it from the handle bars as suggested above. There could be pinch in the wiring making it short out.

[wizzy]

thanks for the info, i just burned the last glass fuse i had so it's off the parts store i go. I should add that the wires to the electric starter are there but when i pulled apart the controle case when i switched over to the cafe bars the button and spring to the starter crumbled apart from sitting so long. i tried to tape the wires apart but i will try to disconnect altogether and go from there.  (?) does he kill switch have any hot/ live power to it, or is it's main function to send a ground signal to the ingition to stop it.

[paulages]

one would reason that you created the problem when switching the bars. given that, i would assume that you pinched the ignition circuit wires somewhere (bl/wh), or hooked them back up wrong in the headlight bucket. power is provided constantly to the switch as long as the key is in the on position. the fact that is is blowing in the run position means that the short is somewhere between the switch and the coils.

i would start by removing the right side hand control, and inspecting the wiring for pinched or bare spots. it the black and white wire you're looking for. did you run the wiring back through the bars, or did you re-route them externally? the short could be in the bars somewhere.

if everything looks fine there, i would inspect all of the black and white wire connections in the headlight bucket. look for something incompletely connected and possibly touching ground somewhere. reinspect all green, black and black/white connections while you're in there.

as for the headlight--do you have a 12v test lamp? i'd start by testing for power at the blue and white connections, just to make absolutely sure your bulb is not the problem. there is a wire that feeds the hi/low switch in the left side hand control (can't remember the colors off the top of my head..red/green maybe?). if this is not connected properly in the bucket, you won't get power to either.

[wizzy]

alright this is what i have so far, the wires comming out of the right hand controls are as followed
black-w/white stripe
2-solid black wires
yellow-w/red strip
black- w/red strip
the only one i can see that is hooked up to the engine run and shut off is on solid black and black with white stripe.  i plugged the black with white stripe into the same color single wire in the headlight bucket, but no matter what solid black wire i plug in is when the fuse blows.  what color should i be pluging the solid black wires to, the other solid black female wires all show "hot" with a test light.

[bryanj]

the black(s) take power to the kill switch and the starter button as the starter feeds power to the headlight(which i seem to remember you saying dont work) or the starter solenoid.

if you just want to get it going connect the black/white in the headlamp shell to any black in the shell BUT you wont get headlights OR starter

[wizzy]

was just in the garage and connected the black/white to solid black power and blew the fuse again when i turned the key to on position.  man this fuse thing has be frustrated.  I should take up stock in the fuse company. any more configurations i could try

[wizzy]

just to note again my electric starter button is missing so i will only be trying to start the bike by kick starter only.
sorry just thought I would add that in.
thanx again for all suggestions

[paulages]

your short is clearly in the black/white circuit, beyond the kill switch. kill switch off- no power. kill switch on- power finds ground, blows fuse. after the kill switch, the black and white wires go to the headlight bucket, then straight to a junction below the coils, where it splits to each respectively. maybe this connection is grounding to the tank?

you might be able to find the ground my hooking your test lamp to the positive side of the battery and prodding around at the black/white connections (all disconnected from each other) until you find one that lights it up. this would tell you which section your short is in.

[oldbiker]

Instead of blowing fuse after fuse, put a 12v 5w bulb where the fuse goes. This will light up when you put the switch to run position because of the short circuit (but it will protect the battery and wiring while you search for the fault) Now you can search along the black/white wire until you find the point where it is shorting to ground (frame of bike). when you find and correct the fault, the bulb will go out and you can now remove the bulb and put a fuse in place safely.

[UnCrash]

Instead of blowing fuse after fuse, put a 12v 5w bulb where the fuse goes. This will light up when you put the switch to run position because of the short circuit (but it will protect the battery and wiring while you search for the fault) Now you can search along the black/white wire until you find the point where it is shorting to ground (frame of bike). when you find and correct the fault, the bulb will go out and you can now remove the bulb and put a fuse in place safely.

Old Biker, excellent troubleshooting tip!!!

[wizzy]

awesome, thanks everyone for the heads up, it looks like i'm off to search alittle further after the headlight bucket. i will keep U posted on the progress.

[wizzy]

FOUND IT!!!!!!!!!!!!!! black/white wire was touching mounting bolt for the brace that holds the coils.  now with that said i have the wire diagram now i rented 1982 copy of clymer service book.  for 72-78 350-550cc hondas, man you should have seen the dust this thing had on it.  so my next question is the blue wire to the headlight should be the drive indicated wire. there is no power to it. i jumped a wire from the battery to the tab where the blur wire should plug into and it iluminated perfetly, the bike still wont fire up, maybe i am not getting spark. the coils look original the blue solid wire to the coil has power but maybe no spark in the plug wires. well any more help would be awesome.
thanks in advance Wizzy

[paulages]

start at your fuse box. test both sides of the headlight fuse, to ensure continuity through the fuse. if you have power to both sides, go to your headlight bucket and look for the brown/red wire. test for voltage here. this goes to your hi/low switch on your left hand control. if you have power to your hand control, but not through it there is  a problem with the switch. i would suspect that you didn't connect the br/r correctly in the headlight bucket.

[WJL75]

As long as you are in the headlight bucket, clean all of the connectors.  It's good maintenance and can clear up issues as well.

[wizzy]

looking at the fuse block my fuses are arranged 5a 7a 15a
and the wiring diagram shows fuses are arranged 5a 15a 7a
which is correct, if the wiring diagram is correct from left to right i have fuses in wrong order, in that case would that have a effect on bike not running or headlight not being on?

[jrtruckn]

If you have power to the coils then I would start with the points. Check the points if you haven't already done so to make sure they are clean. If you have a timing light that in my opinion is an easy and quick way to check for spark in the plug wires. I wouldn't suggest grabbing a wires like I did. It can smart if you have bad wires! If they are original coils and wires and you believe the wires covering hasn't broken down that your losing your spark out them then I would remove to the boots that plug onto the spark plugs. These boots screw on so you may want to remove them cut a little (1/4") off the end of the wire and screw them back on to make sure your getting a good connection to the caps. Another thing you can do (AS LONG AS YOU DON'T HAVE A GAS LEAK!!!) is, if you have an extra spark plug laying around pull the cap put the plug into it and ground the threads to the engine block. Make things as dark as you can and if your getting spark you should be able to see it.  Thats the way I found out that the PO on my 74 550k had switched the wires between the points and coils. 1-4 were firing when 2-3 should have been and vice versa. Once I switched them and knew I had spark it fired the first time. Not good but atleast it ran and I knew I had accomplished something. I then got a used timing light and that helped me tune it. Good luck!

[Patrick]

Pull a plug, ground the plug electrode to a bolt on the frame or the cylinder head and turn the engine over. If you have spark you should see it. Try that with either the one or four, then either the two or three. The one and four run off one coil and the two and three run off the other. If the plug sparks when grounded to the frame then your problem likely lies elsewhere.

Patrick

[paulages]

Pull a plug, ground the plug electrode to a bolt on the frame or the cylinder head and turn the engine over. If you have spark you should see it. Try that with either the one or four, then either the two or three. The one and four run off one coil and the two and three run off the other. If the plug sparks when grounded to the frame then your problem likely lies elsewhere.

Patrick

unless i missed something here, spark plugs aren't gonna turn his headlight on.. 

wizzy- i think the fuse arrangement on my '76 550F is the same as you are describing: healight, tail, main. in any case, this would only affect the headlight if its fuse was blown. too high or low a fuse will only affect the fuse's ability to do it's job: blow before anything else in the circuit does to prevent damage.