No spark. At all.

[Bentwrench]

Okay, so I picked up a 1978 model XS650 about two weeks ago. It was running (rough, I've been told) last fall, and then was stored under a tarp outside all winter, due to too-many-project syndrome on the part of the former owner. The bike is complete, and looks in pretty good shape, but so far, after much lurking and usage of the search function, I can't get spark. Here's what I've done:

1. Cleaned the carbs. Not an electrical troubleshooting step, I know, but they needed it, so I did it. Twice.
2. Replaced the battery. The old one had frozen solid, and the cells were obviously low. Couldn't hold a charge. So I ordered a new one from Mike's XS, and charged it up with my AGM-safe trickle charger.
3. Cleaned and regapped the points. Great write-up on this site, thank you.
4. Tested the engine kill switch. It's working as required.
5. Checked all my fuses. One of the POs replaced the fuse block with individual fuses - they all check out, and as I said, the bike was running with the replacement fuses last fall (as in, the wiring to replace the block is not currently under suspicion.)
6. Checked the plug wires and boots. They work and have resistance as required.
7. Coils... well, I've tried to test them. They seem to be working as required, as in either they're both blown, or they're both fine. I have to admit, the instructions I've found here to check coils are a little confusing. As far as I can tell, there are really only three connections to them - two small wires that attach to the harness, and the plug wire. There is infinite resistance between the two small wires, and I'd have to recheck, but there's some resistance (but not infinite) between the plug boots and the small wires.

And that's it. I'm not sure where to go next. With an engine not running (although my started does work) I'm not sure what's the next likely culprit. I'm willing to bet it will be a common connection for both cylinders, as the bike was running less than a year ago.

Any suggestions? Please help. The suggestion that gets my bike running wins at least a pint of beer.

 

[DogBunny]

If you have infinite resistance between the two small wires, then the primary coil winding has an open and is no good.
On a stock 78 coil, the resistance between the two small wires, the brown and the orange, should be somewhere around 4.4 ohms.

 

[retiredgentleman]

The 2 small wires on each ignition coil should measure around 4 ohms. If they measure infinity then they are junk.

Even if those old coils measured OK I would get rid of them. Buy a new single ignition (dual output) coil along with new plug wires. Those old coils only had about 12K volts when new, and probably even less as they aged. A new coil will give 30K volts or more. Look for a coil with a primary resistance of 4 to 5 ohms.

If you want to continue to use points, you can use them with a new single coil, just by connecting the 2 sets of points in parallel.

I prefer Coors light

 

[Bentwrench]

Ah - sorry. I shouldn't have tried listing results from memory. Just went into the workshop, and both coils are reading a consistent 3 ohms on the small wires.

No beer yet. And Coors light - really? Ah well - no judgment...

 

[Bentwrench]

Oh, and an ignition upgrade is in the cards. But I'd like to confirm the bike is running with it's current gear before putting more money into it. I mean, besides replacing things that have simply stopped working...

 

[Bentwrench]

Scanning the wiring diagram, there doesn't seem to be much left. I should be able to test from the coils to the kill switch, to the fuse, right? And where do the coils ground to?

 

[Bentwrench]

So, here's where I'm at.

I traced the wiring diagram, and figured that if I close the points, turn the key to on (with the battery out), I should have a complete circuit to the appropriate spark plug. And I do. On both sides.

Which means that either my new battery is no good, or my coils are not sending what the plugs need. I suppose my plugs could be bad too...

Unfortunately my multi-meter only measures volts in 10s and 250s, so checking a 12 volt battery accurately is beyond it. Time for a new tool.

And I'm about to go to my wife's family's cottage for the weekend. Which means it will all have to wait until next week.

But in the meantime, is there anything else I could be missing?

 

[Bentwrench]

How about the condenser? I was looking at ignition parts on Mike'sXS, and spotted replacement condensers. It would fit my "one point of failure for both plugs" puzzle piece... a search of this site doesn't show an easy solution thread for testing this part.

LOL - 5th post in a row...

 

[hmusket]

A quick question,just to save you from 6 posts in a row, have you checked the voltage at the coils connections?

 

[Bentwrench]

I have only checked the resistance at the coil connections. How do I check the voltage?

 

[Brian902]

R/W (red/white) wire should have 12 volts with key on and volt meter positive lead on this connector and negative lead on a good ground.

If not 12 volts, make sure no other kill switches are on. If less than 12 volts, test battery to see what it's voltage is, the two should have be equal. If not you have a bad connection somewhere in the system.

In another post I suggested running a positive wire from the battery direct to the R/W wire for a quick test.
You need to put a fuse in this test wire or else you run the risk of shorting out something the first time you touch the live wire to ground. Murpyh's law, that will happen at least once. One bad short like that can destroy electrical equipment in a Heart Beat.

Don't leave this test wire hooked up for anything more than a test as it is drawing power all the time and will eventually kill your battery.

Hope this helps.

 

[hmusket]

In your first post you said you cleaned and regapped the points, did you also check the timing? Are you sure the points are openining and closing?

 

[Bentwrench]

We have spark! Kind of!

So, the PO came by, and we went through the system. One coil is junk, we re-cleaned the ground, checked the condenser, and finally got spark on known good plugs from my XS400.

Unfortunately, the 400 plugs don't fit the 650, so I'll have to wait until I can replace that last piece.

Out of curiousity, how do I check the timing when the bike isn't running?

 

[Bentwrench]

Plugs in, and she fired up almost immediately! As in, I only had to glance at the starter, and she worked! Then the kicker, which I'll likely use most days, which also worked beautifully.

So, it was lots of things, and it seems I owe myself a beer. Good deal! Thanks for all the suggestions and help!

 

[XSLeo]

In your repair manual it tells how to set the points, you set the gaps then use a tester of some sort. I use a 12 volt light bulb. solder some wires to it. One to the side of the metal base, that's ground. One to the dot in the center of the base, that's positive.
Now attach clips to the wires. Hook the ground to a fin on the engine. Hook the positive to the points you want to time.
Line up the timing marks so the rotor mark is half way between the to F marks.
Do the upper set first. Now with the key and engine stop switches in the run position, a loosen the screws holding the main breaker plate, turn the plate so the light is on. If it won't come on rotate the engine 360 degrees till the timing mark line up again. Now slowly rotate the plate back till the light just goes out. This is the point the points open and fire the plug.
Noe rotor the engine over a few times and watch the light, it should go off every time the rotor timing mark is between the F marks.
Now do the lower set. These are mounted on a half breaker plate. repeat the procedure as you did on the upper set.
It may take a bit of fiddling to get the two sets of points to fire at exactly the same but it helps the bike run better. Getting them so both occur between the two F marks is acceptable.
It will take time and patience to get there but worth the effort.
Leo