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Allan G, bill50cal, Gordon Gray, kevin, MikeG, NickL
Total Likes: 33
Original Post (Thread Starter)
by Gordon Gray
Gordon Gray
I put this in the general forum but the bike I’m asking about is a 1967 B44R. Boyer with POD and is wired negative earth.

Earlier this year the bike was running fine. Starting first kick and idling smoothly.
Then it stated “popping” on deceleration. Sort of the same thing you get with an air leak at the head/pipe connection. But the “pop” seems to be deeper in the engine ( if that makes sense?) Just not exactly the same sound as an air leak at the head pipe. The bike started and ran fine until after lunch and it wouldn’t start. Long story, short……I changed the plug and the bike started and ran fine without any popping.
I figured I had solved the problem. It had a NGK plug in it and I replaced that with a lightly used Champion (both were the correct stock heat range)

Well this past weekend I take the bike for a ride and the popping has returned. Probably put 300-400 miles on it since the plug swap. I’ll keep running it like it is to see if it finally won’t start….and then swap the plug again.

I can’t say for 100% sure if the champion is going bad but that popping is exactly what I was hearing last time.

Any idea what could be happening???? I’ve never run across this before….or even heard of it.

Can you kill a spark plug…. and if you can….how? Coil?

Gordon……I’m not a robot.
Liked Replies
by Lannis
I've got a bushel of dead spark plugs out in the shop, some back from my Yamaha two-stroke days.

I've experimented with some of them. Screw two clean, used, gapped NGK plugs into my Firebird - just gives an occasional pop. Screw them out, screw in two new Champions - starts first kick and runs perfect. Screw out the Champions, NGK back in .... just gives an occasional pop.

Tiller starts farting, popping, won't run. Take plug out, clean with solvents, check the gap, carefully clean with crocus cloth, wire brush, etc until it looks like new. Won't run. Screw in new plug, runs perfect.

In my experience, once a plug gets gas-fouled, i.e. trying to spark while wet with gasoline from flooding, etc., it will never work again no matter what you do to it, no matter how clean you get it, even if a spectrometer can detect no hydrocarbons on it ... it's dead.

I'm saving the dead plugs in case some technology comes along that can clean them. I'll be about $600 ahead!

2 members like this
by bill50cal
How about a ride up to my place plug in hand
2 members like this
by Andy Higham
Andy Higham
The worst thing you can do to a spark plug is clean it with a wire brush!
The brush will leave deposits of metal on the insulator causing tracking.
2 members like this
by Twin Pot Phil
Twin Pot Phil
Nick, when I ran the TZ we noticed that a previously fouled and cleaned plug reused gave a different reading to the others that were not 'seconds'.
The historic would just be OK on 'seconds', I suppose because being air cooled the plugs ran much hotter and burnt any gunge off, although the historic ran on 100% Avgas and the TZ was on the best pump fuel.

What we did find with the TZ was that NGKs had a much wider heat range compared to Champions, this was also what we found with the historic.
2 members like this
by quinten
Originally Posted by kevin
thats the case with non resistor plugs. resistors dont work as well with magnetos, but theyre an "improvement" for everybody else.

who runs magnetos these days, besides us and aeroplane people?
resistor plugs are fine with many Magneto's , just not Magnetos on the edge of not working .
( by default , antique magnetos probably fall into this class )

a resistor plug slightly increases the voltage needed to fire across the spark plug gap
... the Magneto coil is forced to hold the primarys collapse , perhaps , a few milliseconds longer
... resistance in series is simple additive resistance ... where the spark-plugs air-gap provides the major resistance .
... meaning you could stress the same Magneto equivalently , by slightly increasing the plugs air-gap .

Who wants a piece of ignition equipment , so sensitive to error , that 5k ohms could break it ?
2 members like this
by NickL
In order to increase the actual spark energy and allow the
spark to have an extended duration it is necessary to increase
the current, the result can be a spark with 100+ mj BUT this
requires a coil or coils with a very low impedance/resistance
primary. Such coils would generate massive heat if used with
a non dwell controlled system, and would burn out quickly.
Typical current on a modern coil is between 8-15 amps This
current is only present for the timed dwell duration normally
less than 2 or 3 milliseconds. The use of a microprocessor to
provide this control is standard practise now but various earlier
systems employed matched coil and control chips to give very
powerful setups. The ubiquitous GM modules were based on
Motorola's MC3334 chip and are a good example.
These facilities became more important as leaner burn engines
were pursued with the emission controls becoming more stringent.
These setups are also very desirable in high compression engines
as to ignite a greater compressed charge requires a larger voltage
to establish an arc across a plug, the increased energy stored in
an HEI type coil enables the gap to be wider whilst also maintaining
the arc for longer. This ensures combustion even with poor head
design / flame path.

Once a micro is available many things become possible so most
aftermarket units have modified timing curves etc so engines can
become perkier without pinging etc.
It is debatable as to whether a standard unmodified 60's British
single or twin would see a great difference between a basic EI or
an HEI type. The timing curve would be the clincher rather than
spark energy in my mind.

Blimey, i can rabbit on eh?
2 members like this
by Cyborg
Long ago, I came across a similar problem. Ultimately it turned out to be the kill switch. I’m not suggesting that is you problem, but it does support your thoughts it may be something like a weak coil. This particular bike was brand new….would run with a new plug, but after some miles it would start to misfire and eventually get to the point where it wouldn’t start. Install a new plug and all was ( more or less) ok again. Turned out the kill switch was bleeding some voltage off to ground. Weird because one would normally expect a kill switch to either work or not. Replaced the kill switch and problem solved. Basically the plug was eventually fouling….helped along by the weak spark. So could be coil or something else in the system.
1 member likes this
by quinten
the right heat range plug .
only works with the right fuel mixture .

plug can get overrly hot , with too a lean mixture
plug may not reach operating temperature , for self cleaning , if mixture is too rich .

or if mixture is right , change the heat range of the plug .
Ethanol can run a cooler plug , 10 or 15% blend shouldn't matter , but maybe does in individual cases ?
1 member likes this
by edunham
My personal experience is the same as yours for singles. Twins and triples (don't have any fours), at least in my experience, seem to tolerate a gas or carbon or oil fouled plug that's been cleaned. Make sure you have a bunch of good plugs handy when you get your C-15 running!

Ed from NJ
1 member likes this
by MikeG
Send it along if you want Gordon (hope you don't have to) and we'll have a session over it. Every coil I've seen go bad got real hot as it failed. I don't know if its possible fir a coil to go intermittently or not though.
1 member likes this
by MikeG
Gordon-aside from the several hundred mile figure, can you give an hour figure? Like it acts up after an hour when you hit that mileage figure, or with less mileage it acts up after riding for 3 or 4 hours or more? Is it the same bike you had at Windys this past May? Is the coil in a place where you can feel it for excess heat when it does act up?

Lannis! I have a plug sand blaster with your name on it.

Originally Posted by Lannis
I'm saving the dead plugs in case some technology comes along that can clean them. I'll be about $600 aheadb!Lannis
1 member likes this
by dave j
dave j
My friends C15 seemed to kill plugs. It used to spit back through the carb a lot so must have been something to do with this. The wrong grade causes spitting back, I read somewhere.

1 member likes this
by DavidP
Tis a puzzlement. Yes, it could be the result of a hot carburetor.
I had some popping going on with my Bonneville. I cured that with larger pilot jets (Mk2 carbs.) So your problem could be the result of a clogged idle jet.
You mentioned that this is your only single with EI. The only time I experienced serious popping was once when I neglected to connect the wire from the regulator before a ride. The Pazon starting popping once battery voltage fell below 11V. I was able to get it home and discover the problem. A healthy battery and charging system are critical with EI.
Ethanol fuel can also cause problems. It throws the A/F ratio out of kilter slightly. Before I changed pilot jets I did notice more popping when using ethanol fuel.

To the original question, can you kill a spark plug. I've killed several using a cutting wheel to remove the metal to inspect the insulator after a plug chop. But I have an otoscope now. laugh
1 member likes this
by BSA_WM20
Unlike old plugs modern ones do not have a lead based glaze on the insulator .
Thus once the first spark tracks down the plug nose it is dead .
Unlike fuels of old, modern fuels are quite conductive at crank case pressure
So if you get the tiniest amount of condensation on the plug nose then the plug will short down the insulator and the plug will always be a problem
1 member likes this
by htown70
Maybe fuel in bowl is getting hot after a bit of riding and causing a bit of vapor lock leaning out the mixture especially on a hot day. Would also make it hard to restart when hot. I had the hard hot restart problem on a 70 Thunderbolt. Solved it by installing a phenolic spacer between the carb and manifold.
1 member likes this
by DAMadd
New singles guy here, and it may be nothing but as a long time auto tech, how about the engine ground. An intermittent ground ( that gets worse with heat) . The other side of the spark plug works thru ground so a corroded ground strap? Not sure how it plays into the positive ground/ei equations, but bad ground + or - isn't good
1 member likes this
by Lannis
Originally Posted by Gordon Gray
Lannis it was a wonderful ride......160+ miles round trip. Bike started first kick every time, and idled like a clock.

Hwy 18 from North Wilkesboro to Morganton.......then Hwy 70 running parallel with I-40. My daughter lives off 70 just outside of Marion, NC.

Mostly two lane.....max speed limit 55.......lovely ride.

The B44R with non stock tire sizes (larger) and 19/47 gearing was very happy putting along a 55 mph.


I'll bet that our grandchildren will always remember Grandpa (or, in our case, Grandma and Grandpa) riding up into their yard, dressed in animal skins, straddling machines propelled by fire....

1 member likes this
by kevin
im racking my brain trying to figure out what might be the issue. a misfiring plug can certainly get wet enough to foul. if you jiggle th ewires when putting a new plug in, that might make the connection again. it doesnt explain why its only on decel. thats whats odd

one thing. they say that EI doesnt always agree with unit singles, for electronic reasons that i dont know much about. i had a boyer on a B44 and it would not run. finally found that the box would not advance or retard. so when i set the timing with a strobe at full advance, thats where it stayed. i put points back in it and it works somewhat better.

perhaps you might try a set of points and see if th eproblem recurs. if youve got other singles to rob just a temporary swap might be instructive
1 member likes this
by DavidP
I've always been a Champion guy. Maybe I missed out on the "bad" ones when I didn't own a bike from 1995 to 2008?
Of course, I've also used "comparable" NGK plugs. I used B8EV and EX plugs in my A65, but they always seemed just a little off in my Triumphs.
The worst was when my regular shop put a set of ND Hot U plugs in my Trident. Ran like crap until I replaced them with proper N3s.
Champion plugs in Triumphs, Motorcraft plugs in Fords, NGK in my Toyota, and Bosch in Volkswagens. That's my story and I'm sticking to it. laugh
1 member likes this
by NickL
I've had the same old set of B8EV's in my beezer for the last 27k miles
around 10 years.
I've put oiled up fouled plugs out of the racer in it every now and then
to clean them, just ran them for a few days, then reused them back in
the racer. They are B8's or B9's either EV's or EG's.
With a good EI plugs are seldom a problem. Experimenting on the racer
with jets etc has fouled them a couple of times on that but normally they
clean themselves ok after giving them a wipe off.
I used to favour Lodge plugs years ago with the racing trumpet as you
could start and run on the same plug, with champ N54's you'd have to
warm up on N3's or 4's. The RL49's from Lodge were great plugs.
1 member likes this
by kevin
thats the case with non resistor plugs. resistors dont work as well with magnetos, but theyre an "improvement" for everybody else.

who runs magnetos these days, besides us and aeroplane people?
1 member likes this
by NickL
quote Kevin
but all an EI does is trigger a magnetic field collapse at the coil. the plug doesnt know what caused the field to collapse, whether it was points, or a transistor, or a monkey with a knife switch. so i dont think the problem is EI. its the plug thats failing, and i think the problem has to closer to the plug itsel;f.

Not quite Kevin, several reasons.

A transistor will collapse the magnetic field more quickly than a set of points.
This will increase the rise time of the secondary voltage.
The faster rise time will overcome fouled plugs more readily.

Controlling dwell will optimise the 'charge time' of the coil thus ensuring the
coil will run cooler at low rpm and more effectively at higher rpm.

There will be no secondary ignition from points bounce.
If you watch a scoped set of points working at over around 3000rpm
you'll see what i mean.

Using high energy type coils will give a larger energy spark, this is only
possible with electronic current control. This larger energy spark can
ignite much weaker mixtures and can give significant improvement in
high compression and performance engines.

There are further reasons electronics are far superior but i won't go into
detail and bore the hell out of you.
1 member likes this
by kevin
this doesnt bore me, nick

i learn stuff here all the time

j just now i learned that the speed of the collapsing of the magnetic field in an ignition coil is controlled by the nature of the trigger as well as by the nature of the coil. i didnt know that

what kinds of coils are you calling "high energy?" that seemsvto ve a term everybody uses for whatever theyre selling.

im using a rebuilt ARD magneto at 7000 to 8000 rpm on a twin-plugged race bike, four non-resistor plugs on two diode-equipped forked plug wires. i have point bounce on it and will be installng a twin-plug pazon i already have.

the pazon comes with two dual tower mini coils is it to my advantage to use some other kind of coil with this unit?
1 member likes this
by kevin
im at the limit of what i can do with old tech, tony. ive had this pazon twin plug unit for several years, and its time to graduate from the magneto and put it in.

coils are the pazon PVLs

[Linked Image from]

the rest of the kit is normal smartfire

[Linked Image from]

but the rotor came out during the time when pazon was messing up the clearances, so i dont know for sure whether i have the old bad one or the new good one.

[Linked Image from]

either way, ill be testing the non-resistor B9ES against the champion N3Cs to see whether theres a difference.
1 member likes this
by BSA_WM20
If you really want to be confused have a look at a "Runtronics" ignition.
They use DC amplification & a cluster spark rather than a single big fat one
Generally used on model aircraft an old customer fitted one to the T100 set up for vintage MX
By the end of the next season 1/2 the bikes were running Runtronics ( or one of the equivalents )
From memory they were not particulalry that good for street racing but bees knees for vintage MX
O has a spin on his Seeley B44 kitted out with ne & that made my B50 feel like a C11 afterwards
1 member likes this
by NickL
Originally Posted by kevin
is the problem that the points arc during the break and so there isnt a clean on/off but rather a period where they are switching back and forth?

To prevent a huge arc across points, a capacitor is placed in parallel.
So when the point break, the arc is extinguished by the energy being stored
to the cap. This action alone slows the transition between states. The
time taken for the cap to charge slows the collapse of the magnetic field.
Also points will have a closed to open transition time with a progressively
increasing resistance, this time is much larger than that of a transistor.
BUT the biggest problem with points is bounce creating secondary ignition.
A well setup maintained advance unit with good quality points and high
quality capacitor of the correct value will be fine but never as good
as a well sorted EI in terms of performance.

I think the pazon unit you have is supplied with HEI type coil/coils as standard,
it is a micro based HEI system. You can easily check, if the coil primary is less
than 1 ohm it's fair to suspect it's an hei type.
1 member likes this
by kevin
those guys are generally way over my head. i just sort of stumble along behind the conversation, but i learn a lot if they talk down to me.
1 member likes this
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