1972 F6....no spark? Help.

flyjosh · Posted: Tue Aug 11, 2009 3:24 pm Post subject: 1972 F6....no spark? Help.

I have a 1972 F6 and it's getting no spark. At least that's what I think. I pulled the spark plug out, hooked it up, kicked it over and I can't see anything that resembles a spark on the electrode end. Am I doing this test correctly?

Second, what should I do to start to trace down the problem? Is it just a bad coil? How can I determine that? Any other advice? Thanks.

jayel · Posted: Tue Aug 11, 2009 5:45 pm Post subject:

need to make sure ignition is wired correctly and key ON works, kill switch ON works, points clean? good plug? plug wire and cap ok?

flyjosh · Posted: Wed Aug 12, 2009 9:51 am Post subject:

I guess I should have included more info. It's been running well for a while. Lately it's been cutting out for a min or so and then it will run fine again. I was thinking it was a fuel issue, but now I'm pretty sure it's an ignition issue.

I'll try some of the things mentioned. But there's no kill switch or points. So, I'm thinking it's a bad connection to the coil, or a bad coil. I'm gonna go work on it now and see what I can come up with.

KirkN · Posted: Wed Aug 12, 2009 12:19 pm Post subject:

Well, the first thing, of course, is verifying the plug itself. 90% of the time, that's the problem.

Sounds like you're doing the test correctly. My preferred technique is to use a pair of needle-nose vise grips to lightly clamp the plug to a cooling fin on the head or cylinder. That way, you're sure the plug is making good ground. Kick 'er over and look for spark.

My preferred "verification" technique is to grab a spark plug out of a known running machine (since I have a stable-full... Smile

) to then verify the integrity of the rest of the circuit on the bike in question. If the known good plug doesn't spark either, then the problem is in the circuitry... The follow-up to that is to then take the questionable plug to the known running bike and repeat the clamp-to-the-cylinder test. That way, if the plug don't spark, you know it ISN'T because of the rest of the circuit.

Both tests are required to prove one or the other or both...

Sorry if that's too basic, but you DID wonder out loud if you'd been doing the test correctly... Smile

Also, no kill switch??? And it's been running well, off and on lately? How have you been shutting it off?

Good luck with it.

Kirk

flyjosh · Posted: Wed Aug 12, 2009 12:37 pm Post subject:

Nope...that's not too basic, that's just what I was looking for. Thanks.

And no kill switch on the F6 as far as I can tell. There's no place on the handlebars for one (it's completely stock), and I can't find anything on the wiring diagram. I just turn the ignition switch to the off position.

Steve Searles · Posted: Wed Aug 12, 2009 1:06 pm Post subject:

Make sure you ground the spark plug base to something, cylinder, frame, etc. That is what he meant by clamp-to-cylinder. Basic again I know.

flyjosh · Posted: Wed Aug 12, 2009 3:00 pm Post subject:

Ok, the latest is.....

1. A new spark plug was tried and the result was the same.

2. I removed the 90 degree boot that connects the coil wire to the plug (pic 1). When the coil wire was touched to the cooling fin, and the engine kicked over, there was a small spark between the coil wire and cooling fin.

So does that mean that the 90 degree boot is bad?

KirkN · Posted: Wed Aug 12, 2009 3:57 pm Post subject:

Sounds like it to me.

If you got a spark to jump from the plug wire to the cylinder when you kicked it over, that pretty much verifies that the entire circuit is CAPABLE of making a spark.

Put on a new boot and give 'er a try.

Actually, to confirm prior to spending any $$, fasten the wire to the plug top somehow, lay the plug base against the cylinder, and try 'er again. See if the plug sparks that way. It should.

flyjosh · Posted: Wed Aug 12, 2009 6:07 pm Post subject:

Why can't things just be simple....arg.

I hooked the coil wire directly to the spark plug and nothing. If I put the coil wire against the cooling fin without the plug, it still makes a spark. So, I'm out of ideas. Anyone got anything else?

I also cleaned the ground at the coil. When I kick it over the headlight still lights up, so the magneto seems to be working. I just tried to measure the voltage going into the coil, but couldn't figure it out. Actually, I may have it hooked up right, but it's very hard to read the voltmeter while I'm kicking it over.

Russell · Posted: Wed Aug 12, 2009 8:44 pm Post subject:

If I leave out the bit where you had the coil wire direct to the plug and got nothing I would have said your issue was definitely the plug cap.
I wonder if the last cm or so of the lead is all chewed out where it connects to the cap?

flyjosh · Posted: Tue Aug 18, 2009 5:06 pm Post subject:

Ok electric guys....more questions for ya.

I thought it might be the plug boot. It's a resister type boot at 5k Ohms. But, turns out that it's fine. I still have a small spark if I touch the wire (minus the boot) to a cooling fine.....but it's a small spark. If the coil was bad, could some voltage still be getting through.....just not enough to pass through the boot? Or is a coil either good or bad?

I can get a used coil for 30 bucks....should I give that a try?

Russell · Posted: Tue Aug 18, 2009 7:30 pm Post subject:

So you are quite satisfied that at the point where the Boot connects to the lead that the lead itself is in good shape and there is a sound contact with the Boot?

flyjosh · Posted: Tue Aug 18, 2009 8:02 pm Post subject:

100%...no. Maybe about 85%. The problem is, if I take much more off, it won't reach the plug anymore. The boot has a threaded needle thing that goes up in the wire about 4 or 5cm. I'm assuming that this is enough to hit at least some good wire. I did take off about 2cm early on. I might see if I can take a few more cm off and see if that works.

Russell · Posted: Tue Aug 18, 2009 8:17 pm Post subject:

I know about the length of lead dilemna. Have the same issue myself with my CB175 and a coil with two leads sealed into the body of the coil. Thats where the 'lead splice' that NGK sells might be useful for you.

jbcycles · Posted: Fri Sep 04, 2009 10:04 pm Post subject:

I've had the same exact problem with a F7 it turned out to be the ignition box... It took 2 used boxes to find 1 good one... comon problem on those models
JB Cycles