Electrical problems, arrrgh!

[pasteurized]

Finally got my '750 basically dialed in as far as jetting with the V&H 4-1 and stock airbox yesterday, and went for a long ride (which was such an awesome reward). Fast forward to last night. Hanging out with some friends, and one suggests I try a bigger (louder) horn that he had on his FZR 600 at one point. Same terminal connections, easy swap. Beep beep, yep, louder! Figured I would switch back to the original and take the louder one home so I could correctly mount it at some point. Turn the key in the ignition to start her up and leave, and nothing. No lights at all. After some careful investigation, I found that I could start/run it by kickstarting (running off the stator, apparently), and found that a fuse was blown that apparently ran to the battery. Shut bike off as it was late and got a ride home. Got the replacement fuses this morning, popped one in, got lights back on the cluster. Set choke, hit start button, and it will turn over as long as you hold the button but will never fire or start. Tried kickstarting a bunch of times too, nothing. Checked battery cables, other fuses in the area, etc, but all looked fine. Being that everything was great yesterday (carbs freshly cleaned, ran like a bat out of hell, etc), I'm thinking that it probably isn't getting spark due to an electrical problem. I need to go over to his place (where the bike is currently stranded) and pull a plug and see if it isn't firing, which is what I expect. But my question is, what died, seeing that it started up last night without any battery connected at all? I went over and tried to start multiple times today in case it was flooded, etc, but it didn't. Also pulled the new fuse and tried to start it off the charging system like it did last night with the kickstart, no go. I will check the plugs (coils) for spark, but what gives??

 

[Steve]

Check your fuses. Here is a cut-and-paste from one of my previous responses concerning fuses:

The top fuse feeds the ignition key, which controls power to the head and tail lights and the turn signals and gauges.
The 2nd fuse down feeds the brake lights, oil pressure switch and horns.
The 3rd fuse down feeds the ignition circuit.
The 4th fuse down is the main fuse. It is fed from the starter relay, which is connected directly to the battery. The regulator/rectifier also feeds the battery through this fuse, so make sure the contacts are clean and the fuse is good.
The bottom fuse only protects the ACC outlet at the bottom of the fuse panel. That should not have any effect on charging.

 

[pasteurized]

Hey Steve, thanks for the input. I will check all the fuses I can either tonight or tomorrow. I looked all over for a fuse box like my '82 GS650 had, and I cannot seem to locate one. The fuse that was blown was right under the left side cover, inline and it looked factory stock. Is there actually a fuse box on a '77 750?

 

[SPARKSS]

Electrical problems, arrrgh!

Hopefully you won't grimace at my reply......having gotten "caught" myself a couple of times over the years. Any chance you bumped the kill switch (which can even hang half-way and on a quick glance look ok???? I've almost never used it on any bike I've owned and noted you didn't mention it when going over what you tried.

 

[pasteurized]

Heh, yes, I have checked the kill switch as well. In fact, I played with it a bit, switching it on dims the cluster lights ever so slightly, so I know it is engaging the "running" circuit.

 

[Steve]

Can't tell you where the fuse box might be as the 750 is one size I have not yet played with. My son has had a 450 and 650, my wife has an 850 and a friend has a 550, and they have all been pretty much the same for fuse arrangement in the fuse box. The box has moved around, but the arrangement is the same.

.

 

[edbot]

The 77 750's don't have a fuse box. Just the one fuse behind the left side cover.

 

[pasteurized]

Damn, that's what I thought. Thanks.

The 77 750's don't have a fuse box. Just the one fuse behind the left side cover.

 

[earlfor]

My first inclination is that the increased amperage consumption of the louder horns burned the contacts in the ignition switch. I suspect you "toasted" the ignition switch.

For installing a horn with a higher power draw, a relay is required.

E.

 

[argonsagas]

I see Earl has already replied with the answer.



Connecting a powerful horn to the circuit directly will almost invariably blow the fuse due to the much higher electrical draw non-stock horns demand, thus the requirement for a relay to operate it.

The wire feeding the horn is a tiny one, (22AWB) and it goes through three splices within the harness before reaching the horn, so it cannot handle much current load and if you keep trying it, or use a larger fuse, you may overheat the wire and damage the harness.


Since you are constantly draining the battery, you might also look at this:

Your horn does not get a "live" feed at the switch. It is the opposite, with the circuit into the horn always live, and the switch providing the ground.

 

[pasteurized]

I understand what you two are saying about the horn drawing too much amperage. When my friend suggested it, I immediately told him that would be the case but he insisted that it would be fine, and sadly, I listened to him.

Any way to test if the ignition switch is the culprit? I get all the lights on when I turn the key, and it cranks like a champ when I hit the starter button...?

 

[earlfor]

The starter doesnt draw power through the ignition switch. Only the exciter wire to operate the solenoid goes through the ignition switch.

I would look at a wiring diagram to determine which output lead from the switch powers the coils/ignition system. Check the lead for voltage with the switch on. Sometimes, there can be continuity/12 volts output but no amperage. Whether the lead shows no voltage or 12v with the bike not getting ignition, at that point I would jump that switch output lead directly to battery positive. If the starts/runs normally, its a pretty safe bet the fault is in the switch. Or, if you happen to have a spare switch, swap them out and see.

E.

I understand what you two are saying about the horn drawing too much amperage. When my friend suggested it, I immediately told him that would be the case but he insisted that it would be fine, and sadly, I listened to him.

Any way to test if the ignition switch is the culprit? I get all the lights on when I turn the key, and it cranks like a champ when I hit the starter button...?

 

[argonsagas]

I am not certain of the wiring on this model.

I would take Earl's advice and check out the switch as well as all connections.

If you cannot resolve it that way you may have to go a more difficult route.

Logic is this way:
Power runs from the fuse box to the ignition switch.
When the switch is "ON" power runs through the switch to the kill button and also to the starter button, as well as to the ignition circuit and lights, although this is likely done through different contact positions inside the switch.

The kill switch controls the ignition circuit, and it is separate from the starter switch, so if If power is available at both the kill switch and at the starter button it should also be available at the ignition circuit.

Apparently it is not, so there must be a break in the circuit after it leaves the switch.

You must check all connectors along the route. Hopefully, you will find one loose and resolve everything. Remember to check both sides of each connection. I think you have a points ignition, so be sure you check input voltage there, and check for voltage at the coils.

Use a meter and look for voltage all across the ignition side. If you have a substantial drop, it may just be a dirty contact, which can be fixed by cleaning. This is not uncommon, and the voltage drop could be the reason for non-firing.

If none of these, and you have thoroughly checked all available connections and fuses, you may have is a problem at one of the junctions inside the harness, relating to the tiny wires that run to the horns mentioned earlier, as they are spliced into several parts of the harness and those tiny wires can overheat easily when too much amperage draw is run through them.

If the splice point got too hot it may have opened a contact, or melted and broke it.

Hopefully, this will not be necessary, and it is a pain to do, but a careful slicing of the harness tape may be all you need to find the connections and repair them.

 

[pasteurized]

Update time... aka, HELP! ;-)

Got to spend some time on it this afternoon. Opened the right handlebar control and checked the solder point from the off/run switch, tested fine. Tested the orange wire that runs from the on/off switch to the coils, tested fine at 12V at the point which they connect to the coils. Next, I checked the points; with ignition on and run rocker switch on, I got 12V to each of the points (when not making contact with the plate). Additionally, checked the wires that run from the points to the coils, and when I got 12V at one of the points, got 12V at the end of the wire where the coil would connect to the corresponding contact point. All ok there. Tried to check for resistance of the coils, but had a hard time getting a good reading. The readings I did get were in the low 4s. But like I said, I don't have a whole lot of confidence in those readings.

One thing I did notice is when spinning the motor over with the starter, I didn't seem to be able to see much of any spark coming from the points when they made contact. I was, however, able to take a screwdriver and move it around between the point and it's striking area and with the ignition on, get it to spark with the screwdriver. No real visible spark on its own though when cranking the motor over.

No spark whatsoever out of the plug wires. I tried a lot of different things. Disconnected and reconnected the wires going to them, replaced one of the coils with an extra I have, even ran a separate wire from the 1-4 cyl point directly to the coil, bypassing the wire in the harness to see if that had any effect. None whatsoever.

Kind of really stuck at this point. The coils are getting constant power from the off/run switch, getting 12v from the points, points don't seem to be sparking much (but apparently are doing their job?) and no spark at all from the plugs. I guess that leads to the coils being bad, but then why didn't my replacement coil fire the plug I connected to it either? Maybe if someone can better explain how the coils/points are wired, I could see if there is something I am missing?

Any input would be great, as I am up in arms here.

 

[pasteurized]

I'm pretty stumped, earl (or anyone else!) have any suggestions on where to go from here? I will be going over there tomorrow afternoon to do any other testing I can think of.

 

[earlfor]

OK, there are some possibilities. As I said previously, you can have 12 volts but with not enough amperage to power anything. For example, you could stack 8 D cell flashlight batteries and get 12 volts, but there is no possibility you could crank your car with that 12 volts.

From your checks, lets assume (for the moment) you do have continuity in all the required circuits since it appears so. We will further assume the points are working properly since points do not usually go bad instantly, but degrade slowly. We are left with good circuits, but not enough flow/amperage. If your battery is showing 12 volts, that level of charge is a DEAD battery. How old is that battery? The battery should show a minimum of 12.5 volts and preferably something around 12.7 or 12.8 depending on the type of battery you have. You will need to have at least 12.5 volts in the battery in any event. Once you have a charged battery, I want you to do a couple of things. Your bike should have an off position for the headlight. Turn it off. If you do not have an off headlight position, open the headlight shell and unplug the headlight. Next, the orange/white lead in your harness that connects to the + terminals on the right and left coils is a single wire in the harness that has a "Y" pigtail on the end that allows you to power both coils. Disconnect the two harness orange/white leads from the coils. In their place, take a 4 ft length of 14 guage or larger wire and make a "Y" pigtail for one end. connect the "Y" end to the coil + coil terminals. Connect the other end directly to the battery + terminal.
This will eliminate any voltage drop the might possibly be in the wiring harness or switches and bypass any voltage drop caused by the ignition switch. Once the above is done (and you have a charged battery installed), Remove the #4 spark plug, reinsert it into the plug cap, ground it against the engine, turn the ignition switch on, and bump the starter. You should see the plug spark. Then reinstall the #4 plug, connecting the spark plug lead/cap. Now remove the #3 plug and repeat the process to be certain you have spark on it also. If you have spark on 3 and 4, then you should have spark on all four. If you have spark, the bike should start and run normally. We would now know the problem is not in the ignition system, but in the wiring and switches.

Let me know what happens and we can take it from there.

E.

I'm pretty stumped, earl (or anyone else!) have any suggestions on where to go from here? I will be going over there tomorrow afternoon to do any other testing I can think of.

 

[pasteurized]

Hey Earl, thanks for your time in replying! I actually just went over basically the same thing with my dad on the phone. He is pretty knowledgeable about points ignitions and crappy electronics systems, due to his experience with British cars in the past (has owned more than a handful of Triumphs and a few MGs). He explained the way that the points system works as far as how the electricity flows through it and it makes a lot of sense now, as I was kind of shooting in the dark before.

I will try your suggestion and at that point it will definitely be narrowed down a bit more. I'll report back tomorrow evening with the status.

Thanks again, I really do appreciate the comments and suggestions. If anything, it's really nice to know that someone else knows what I am talking about, and that gives me some courage in my attack

 

[earlfor]

Once you understand how it works, it usually a simple thing to isolate and verify each compenent along the line is working. We'll get you there, its just going to take a few checks and eliminations of possibilities. LOL
Lemme know.

E.

Hey Earl, thanks for your time in replying! I actually just went over basically the same thing with my dad on the phone. He is pretty knowledgeable about points ignitions and crappy electronics systems, due to his experience with British cars in the past (has owned more than a handful of Triumphs and a few MGs). He explained the way that the points system works as far as how the electricity flows through it and it makes a lot of sense now, as I was kind of shooting in the dark before.

I will try your suggestion and at that point it will definitely be narrowed down a bit more. I'll report back tomorrow evening with the status.

Thanks again, I really do appreciate the comments and suggestions. If anything, it's really nice to know that someone else knows what I am talking about, and that gives me some courage in my attack

 

[pasteurized]

Ok, here is today's update:

Bypassed the ignition/kill switches by running a lead directly from the battery to the orange wire on each coil. Additionally, I ran leads from each point to its respective coil, essentially bypassing the wires that run from the points to the coils that snakes around the frame. No consistent spark. There were two separate times that I got spark from one of the plugs (#4), but it was not very consistent and once I let off the starter button, it would not fire again. I tried all the different plugs and was not able to get any spark out of any of them. This was in the garage with all the lights off, so it was pitch black. I was able to see some spark from the points but it was weak spark and it didn't seem very consistent. Tested the condensers via the resistance method and they both checked out just fine. The battery was pretty worn out from all the starter spinning after a bit, so we temporarily added jumper cables from a car battery (not a running car) to the bike's battery and even though the starter would spin quickly again, no go on the spark.

I guess at this point I would have to say both coils are shot. I don't know how both would die simultaneously. One more thing to throw into the mix is that I have an extra coil that we swapped in place of one of my bike's and it failed to show any spark as well. I don't know the status of this coil though, as it was a used piece that I have had in a box for a few years.

I wish there was something that would just shout out to me "order dyna coils!" and I would go ahead and do so. Normally I would have just bought Dyna Coils and a Dyna S ignition and done this right, but with my wedding a month from tomorrow, I want to be pretty dang sure that what I buy will fix it.

 

[earlfor]

OK, you're installed jumper wires fromthe battery to power the coils and jumper wires from the points to the coils. You have eliminated any possibility of it being a switch or wiring harness problem. You have added the battery capacity of a car battery with a jumpers and the electric starter spinning over quickly proves there is plenty of amperage available.
So............. The problem is either the pointsets or it is the coils.

I have a "birdie" in the back of my head telling me there is a possibility the rubbing blocks on the pointsets have worn down and your points are not breaking with enough of a gap. If you have spare replacement pointsets, it would be best to install them, gap and set static timing. If you dont have replacement points, gap the old ones and reset static timing.

Check the coil resistances. I know you said you tried and didnt get a good reading, but................ that doesnt tell us anything. LOL Set your multimeter to the ohms scale (looks like a horseshoe). Set it to the lowest scale that includes any value up to 6. The resistance between the terminals on a coil should be 5 ohms. A slight variance is not a problem.
Now set the meter to an ohm scale that will include a value of 50,000 (50K).
Check the resistance between the contacts in the 1 and 4 plug caps and then between the 2 and 3 plug cap contacts. The reading should be between 30,000 and 50,000 ohms (30-50K) If the coils are in this range, they should at least work long enough to start the bike. Old coils may break down after warming with for a minute or two, so the test does not guarantee good coils. If they coils are bad with good reading, they should at least function for a short time.

Check the point gaps and static timing first to make sure it is correct, then check coil resistances. If all seems within specs, it should start.

Lemme know.

The cheapest way out of this mire probably would be to buy new coils and new points. The best solution is new coils and a Dyna S ignition.

E.

Ok, here is today's update:

Bypassed the ignition/kill switches by running a lead directly from the battery to ............................................