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Beginning last December, my engine was developing a slight hesitation just off idle.  I'd step on the gas pedal and I would get a dead spot for a fraction of a second then recover, almost like a POP! but in reverse.   The engine ran really smooth in any gear at anything over 1,500 rpm and sounded great.  This season, the hesitation was getting more frequent, so I suspected the coil.  

After I cleaned up all the electrical connections and swapped coils, nothing really changed much, and if I lugged it a bit in 4'th on a slight uphill it would do it repeatedly but randomly.  Not like it was the same cylinder all the time, but it seemed to be jumping around.  What was especially concerning was taking off out of an uphill stop and it was like it coughed once, bogged and then took off and that's not good!

So far, I have:

-  Pulled the carbs and, on the bench, pulled the jets and shot some carb cleaner through them and then blasted in from the mixture screw holes - No real change.

-  Installed new gaskets at the carb base AND at the intake manifold base - No change

-  Checked the sync on both carbs and they were dead synced - No change

This morning, just on a hunch, I stopped at my FLAP store and bought a new set of NGK BR6HS spark plugs for $20 bucks (that's the plug Pat Downs recommends).  Gapped them at .025" as recommended by Bentley (actually, they come pre-gapped) and put them in (which sounds easy, but this is a CMC where it's a real PITA to even see/feel, let alone get to, #1 & #3 ).  

Miracle of miracles!!!  It was the Twenty Dollar Cure!  All of the hesitation is gone!!  It was actually a pleasure driving around on back roads at slow speeds, again!   Amazing what a new set of plugs can do.

Then I checked the gap on the old plugs, which had been in there since when I ran the MagnaSpark I, back when I had the big, clunky, MagnaSpark I HEI coil and they were gapped at .032" because IIRC, CB recommended that gap with their old coil.  But now I'm running a new, more-or-less-stock, NGK coil which isn't as "hot" as the old MS I coil, so the .032 gap was just a bit too much for it and it was running as if it needed a tune-up.  

So, the lesson learned is the plug gap should be matched to the voltage output of the coil and maybe checked so often - It makes a BIG difference!

Now just watch....   Now that I've written about it, it will probably screw up again, just to spite me.

Last edited by Gordon Nichols
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It's been buggin' me for a couple of weeks.  Everything somehow sounded familiar from the dim, dark past, when everyone was running points and carbs and lots of people knew the tell-tale warning signs of points, condenser and plugs wearing out.  

This never really felt like it was a carb problem.  Just some of those nagging things from 50+ years ago that said "It's the Ignition, Stupid!"  and Stan telling us that 95% of Carb problems are ignition.  Hence, trying the new coil - It was an easy swap.  

Never occurred to me that the MagnaSpark I coil was "hotter" than the MS II version (which is also half the physical size) and I needed to adjust the plug gap to match - Until last evening when I realized that the symptoms were just like an engine needing a tune-up.  The only thing left was plugs, so for $20 bucks (and $35 for the coil) I'm not out much.

I used to run Platinum-tipped plugs in Pearl, but both Pat Downs and the guy who rebuilt my carbs dIdn't like them.  All we used to run on our snowmobiles and motorcycles were Platinum tips and we loved them - they seemed last almost forever.  Anyway, I switched to regular tips and forgot that they don't last as long.  I made it worse by leaving the plug gaps really wide for this coil, too.   Live and learn.

Something else to consider:

Many years ago, i switched from an 009 to a Mallory Unilite distributor. The Unilite (like the Magnaspark and PDP's Shockwave) run different distributor caps -- with the little t!ts (described such that you know what I'm talking about, but NGK calls them "terminal nuts") on them like a normal spark-plug would have. All of them then use the different (non-Bosch style) plug wires.

The 7mm Bosch wires don't want that little "terminal nut" on them, so the NGK plugs we all use ship with a removable little "terminal nut". The "terminal nut" ship loose, threads on the plug, and then the wire snaps on.

That "terminal nut" can easily loosen, and you can't really use loctite on the studs because loctite is an insulator. I chased an intermittent miss for almost an entire summer that turned out to be a loose "terminal nut" on one of the plugs. It would make contact... mostly, but sometimes not.

Just something (else) to keep in mind. If it's been done wrong, I've done it.

Last edited by Stan Galat

@Gordon Nichols, how many miles were on the plugs?

6K - 8K miles, tops.  The plugs don't look especially old or fouled or anything and they all look about the same.  If #1 and 3 weren't such a PITA to get at I would consider re-gapping the old plugs and putting them in, just to see what happens.  #2 & 4 took maybe 2 minutes each while the other two were closer to 15 mins each.

I am glad you found it, Gordon. It totally makes sense.

My plugs are gapped at 0.040", but I can do that as I use a coil pack which has a pretty hot spark. It's off a later watercooled VW Golf/Beetle.

I also use those screw-on "terminal nuts". I installed them with tiny little lockwashers and used vice-grips to snug them up. Hope that helps.

"If it's been done wrong, I've done it." Copy that, loud and clear.

I like the Bosch (?) style long Bakelite plug wire ends with the little spring thingie in there that rides over the threaded ends of the spark plugs, sans nuts.  The bakelite ends give you something to grip on to and push or pull to put on or off.  I went full system gear with my Magnaspark, including wires and terminals.  No more bakelite terminals. and I'm going to say getting the wires properly attached to the plugs was a pretty iffy thing, seemed to me. Too much wobbly rubber, little tactile feedback about how it was all going. And the hole covers for the tins left a lot to be desired, IMHO.  Did not really fasten in like I thought they should.  Finally, as to gap, I dont remember what was done there.  Its likely that the gaps are a little short for the Magnaspark system, which includes their coil pack.  All that said, the new "system" seems to work as promised.  No issues so far.

If #1 and 3 weren't such a PITA to get at I would consider re-gapping the old plugs and putting them in, just to see what happens.  #2 & 4 took maybe 2 minutes each while the other two were closer to 15 mins each.

Have you ever gone at them from the bottom? I made my surround tin in three pieces, if I take out the side pieces, you can get right to them from underneath.

Last edited by Stan Galat

@Stan Galat. My heat shield is similar, but one big horse shoe in shape.  I found out long ago that swapping plugs with the shield out was a breeze from the bottom and almost pulled it out this time, but managed to swap the plugs and get 1 & 3 snugged up tight with only moderate grunting and contortions (and no swearing this time, either!)

I recall Carl Berry installed some sort of marine style inspection covers in the wheel well wall for plug access, which is a good idea, but 3-piece removable heat shields would be just as good.

Interesting facts about ignition systems:

You don't need resistor ANYTHING unless you have a radio or some other sensitive electronics in there(such as EFI or electronic ignition or crank fire/distributorless).

If you do need a resistor element in your system, it can be plugs, wires, or the rotor. You only need one element to be the resistor. I don't think more helps here, and I don't think it hurts either.

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