I had the same problem with NGK plugs, it was talked about on another post recently. I tried a few new NGK plugs in my Manx, they had a weak spark then nothing. I tried an old lodge plug and it had a good spark. I've also had similar problems with NGK in my Dommie, but they work well in my Commando. I think they don't work well with magnetos, probably due to resistance although they weren't resistor plugs. I don't know what heat rating an M20 is but Norton singles are about a 6 in NGK and N5 champion plugs

email (option): horror@blueyonder.co.uk

I use only Champion plugs, and as a general rule, I put L86C in my SV's and L82C in my OHV's. I can't remember what the 18mm plugs are in my Norton's but they are still Champion. I buy my plugs quite cheaply (on line) from http://www.gsparkplug.com/

Ron

email (option): ronpier@talk21.com

Hello Ian F.

I also had some problems at the past with sparkplugs.
In my case they did work, but I could only start the motor for a short while,
(I mean- 2 minuets or less)
And then there was no more spark, no matter what I did to the sparkplug-
Clean, burn, adjust, burn in fuel in order to try and maybe dry it... nothing.
An entire box went like that, but I cannot remember which brand it was.
Anyway, a plug of another maker did work perfectly.

Regarding the heat level of the plug,
It does not have to do with the fact of whether or not the plus sparks,
But with the heat distribution on the faces of the barrel head:
Colder s.plugs disperse the heat in a "shallow" manner, whilst hotter plugs
"Suck" the heat higher, keep more heat, and only give away some heat to the
Head surface.
The heat rating is usually determined by the shape of the ceramic insulator around the electrode.
It can also make damage if using the wrong temp rate, such as melting
The electrode of the s.plug onto the barrel if using much hotter plug,
Or soot accumulation if using too cold.
Nowadays, many makers recommend slightly different heat ratings for different climates.

Wishing you all a very happy new year,
And a great thank you to all of the contributors and to dear Henk.
Noam.

email (option): noam10"at"gmail.com

NGK always had questionable durability for racing (cold plugs - around 10 grade) fine in the TZ but always needed something much hotter running than expected(lower number ... 6/7/8 as opposed to 10 grade) in Manx, Triumph etc.
They had a bad habit of simply 'lighting out' and stopping working.
We always use Scitu rev counters and these alwasy give us warning when a plug is on its way out.

Not helped by all the copies now on the market (EV/EG price - std plug supplied!)

Yes old lodge work well into thier old age.

Bosch seem to be reliable and have various electroded set-ups - i am currently using the twin earth plugs in the B25 and these give much better 'bottom end'.

CHAMPIONS - similar to Bosch, but i never had any luck with their 'hard/cold' racing plugs for some reason.

Ford 18mm plugs i think from a cortina, (complete with taper seat - just dont over tighten them) work fine in the ES2 norton, for many years so far.

I usually run BP5HS in my M20.
You do need a hotter plug with this rubbish they call fuel now days.
Fuel is very conductive at cylinder compressions so once damp will condust quite happily and this is made worse by the fact that insulators are no longer glazed.

Breaking in new plugs is the worst and it is not uncommon o have them go bad direct from the box.
I have also found that shutting down the engine by turning off the fuel seems to give a lot better plug life

email (option): bsansw1@tpg.com.au

Thanks for the info. on the M20 plug grade for the Trevor...Handy to know.

I've always run Champion plugs myself without any hassle...Saying that though, I had a new one go duff just the other day in the TRW...

The bike was running OK when I put it in the workshop..The next time I went to use it, it fired up on one cylinder. I replaced the plug (same type and grade) and have had no further problems... ...Ian

email (option): ian@wright52.plus.com

Hi All
Had some interesting problems with spark plugs on my R60 BMW - thought I'd try some Denso iridium thin centre electrode plugs as they are supposed to spark at lower voltage (to help the 55 year old magneto!!) well they did initially start with hardly more than just turning it over but then the left pot stopped while out running. I thought of a dead plug but found that what ever thin electrode plug I put in the left cylinder would stop after a few Km but would work again if swapped to the right pot!. I then swapped the HT wires on the mag so the cylinders were firing off the other ends of the HT coil. Guess what - the failing then swapped to the right cylinder. Only explanation I have is that the spark is of opposite polarity from each end of the magneto ht coil (it fires both cylinders - flat twin - on each revolution one on the exhaust stroke) and the thin electrode plugs dont like sparking backwards from the earth electrode. Have gone back to ordinary plugs with no problem!! Also years ago I had an A7 Kawasaki with rotary disc induction fitted with Kawasaki racing steel discs and that was very hard on plugs (10 grade NGK) NGK were about the only plugs that would work but probably part of the problem was the lead in the fuel as it went ok on lead free avgas - still very hard on the plugs.
You used to be able to get a little clear plastic gadget that had three pointed electrodes in it that was used to check which polarity the spark was - cant find mine now!!
All the best for the New Year
Doug W

email (option): watsond@xnet.co.nz

Wow! Thanks for the input here guys :-)

I'll give a BP5HS a try and see how we go...

NGK = "Now Gone Kaput"

email (option): fozzie001@hotmail.com

Is this listing correct.. Alternatives to the NGK BP5HS??

Brand Model
AC Delco 44FFS
AC Delco 45FFS
AC Delco 46FFS
AC Delco B44FS
AC Delco R43CFS
AC Delco R43FS

Bosch 0 241 229 578
Bosch 0 241 229 641
Bosch 0241229578
Bosch 0241229641
Bosch W145T35
Bosch W6BC
Bosch W7BC
Bosch W8AP
Bosch W8B
Bosch W8BC
Bosch W8BP
Bosch WR7BC+
Bosch WR8BP

Champion L11YC
Champion L12Y
Champion L89CM
Champion L92Y
Champion L92YC
Champion OE059
Champion OE059/T10
Champion P-L11YC
Champion RL95YC

More research here:-
BSA M20, M21 (Cast Iron Head) Original Champion: L10 Modern Champion: L86C NGK: B6HS

As I have a cast iron head, should I be running with a BP6HS plug or it's equivelant?

email (option): fozzie001@hotmail.com

Yes and no
That is the list of plugs with operating ranges tha overlap all or part of the operation range for an BP5HS but not necessarity the exact equivalent plug.
So a BP 5 will cover 3/4 of the range of a BP 4 or a BP 6.

So that is the list of plugs whoes operational parameters overlap some ( including all ) of those for a BP 5 and have the same physical dimensions.
The closest direct crosses heat range wise are :-
Bosch W8's ( all of them ) the WR are resistor plugs
Champion L 11 & 12


As I previously mentioned to avoid fouling you need to run hotter plugs than originally specified.
OTOH if you have a stash of original or NOS 1950 petrol the the B6HS is the correct plug

The new plugs have projecting electrodes which is what the "P" stands for but when your bike was new there was no projecting electrode plugs and the center electrode ends flush with the end of the body so both of the plugs shown in Noams post above are Projecting Electrode type.

Similarly the Y champion plugs signifies a V grove in the earth electrode again a new feature since M20's were made.

I can not remember the nomentlacture for all the plug codes as I only remember the bits I need. There is another code depending upon weather the top of the plug has a solid cantact or a screw on cap so there is not as many plugs at it would seem.

email (option): bsansw1@tpg.com.au

Ian - i would say that you should be somewhere between a 6 and no 'harder' than an 8.
To be honest, too 'soft' (hot running) plug makes very little differance unless you are running on the ragged edge.

AV gas is full of lead, so don't think its lead-free - TetraEthyele lead (or whatever) is what enabled the RR series of engines produce the power they did, on ever higher boost pressures.

I had a Kawi Samuri an Avenger - yes they were hard on 10 grade plugs, probably due to a marginal ignition system .... but it made no difference if you left 8 grade plugs in (did'nt foul) and did'nt swap to 10 grades as recommended in the typically conservative Japanese instruction book.
All the triples, the next generation after the above had CDI and were completely reliable. However any idiot can f**k-up the best of bike.

I cannot believe some of the stuff about 'running in plugs' etc, where do does this stuff come from?
For damn near 50 years i've raced bikes, on everything from AvGas to NitroMeth. and back again and NEVER had plug trouble, other than caused by the ighition system, or self-inflicted (TZ running 20:1 R, when running too rich for the conditions).

a Cast Iron SV will run hotter than most things - in otherwords it burn off any deposit's.
Yes the center electrode can overheat, increasing the electrical resistance and hence, with a weak mag, cause a misfire - which can often rectify itself when everything cools down.

But think of your humble lawn-mower ... mines not had a plug in 20 years and i feed all sorts of fuel into it (2 stroke usually from the enduro bikes).

Thanks again guys - Trevor especially - your information has filled in a lot of blanks in my knowledge base :-)

email (option): fozzie001@hotmail.com

Hi

If anyone is interested, I still have a small number of uk manufactured champion plugs
L 86
L10
These plugs are NOS and for what ever reason, materials used I suspect, perform better than modern L 86c replacements available these time

Drop me a PM if interested

Job

email (option): Jonnyob1@googlemail.com

Modern engine burn a lot hotter .
Hot enough to melt the glazing on the center electrode so modern plugs have unglazed insulators around the center electrode.
As thus they pick up and dold fuel deposits which ae highly conductive at compression pressures. This is why a lot of plugs seem to be "bad" right out of the box.
They can not be mechanically cleaned and can only be burned off that is heated up enough to vapourise then ignite the fuel.
This is also why instruction for the maintnance of small engines say to replace the plugs at regular service intervals, not clean & regap as was done with old plugs.
So your NOS plugs with insulated noses are worth holding on to becaue you can not get them any more.

email (option): bsansw1@tpg.com.au

I think 'replace rather than clean' is more to do with selling plugs than anything else?

As for the insulator in the middle of the plug, i've never seen a 'glazed' one - and a friend collects the damn things !

Plug fouling, which became a problem in the 50's with the increase in 2 stroke numbers, has been blamed on petrol additives (mainly lead) and oil additives (mainly zinc) - both of which are no longer used as they mess up cat's.

The lack of zinc in engine oils is one reason for the 'special oil' requirement in VW/AUDI engines - to prevent camshaft wear - and that comes from VW themselves!

I ordered a couple of Champion N5c plugs in the vain hope I may get close to finishing my 1958 M21 project later this year but when they arrived I see they are badged as "copper plus".

The blurb says "Allows for accurate control of heat range. Copper core center electrode also optimizes the performance and longevity of the Spark Plug". Not sure they're optimised for a 58 year old side valve though - anyone got any experience of these?

Gary.

email (option): gj.owen@hotmail.co.uk

email (option): bsansw1@tpg.com.au

Getting back to Ian's original post might suggest you check that the inlet valve is not closing the plug gap to zero when you kick it over? This would explain why the unfitted car plugs sparked. Also, protruding earth electrodes would almost certainly contact the valve especially if the head or cylinder face has been skimmed.
Richard

Gary Owen

I ordered a couple of Champion N5c plugs in the vain hope I may get close to finishing my 1958 M21 project later this year but when they arrived I see they are badged as "copper plus".

The blurb says "Allows for accurate control of heat range. Copper core center electrode also optimizes the performance and longevity of the Spark Plug". Not sure they're optimised for a 58 year old side valve though - anyone got any experience of these?

Gary.

email (option): martynhillyard@msn.com

years ago you dumped them in battery acid to remove metalic residue .... did'nt do any good though.

All based on wrecking literally hundreds of plugs in everything from aircraft engines to hydroplanes and everything between ................
No suprise i had NGK sponsorship for a couple of years (still used champion plugs though ...)

And i still bet its to do with selling plugs ..........

Getting back original question - could be a valve closing the electrode gap - i have a tendancy to use extended nose plugs in engines - does give better tick-over and starting, but with a B25 the piston can hit the plug.
Had it happen the other day, its happily raced (the same) long nose plug all season - fitted a temp. sensor washer under the plug .... and it hit the piston, despite being further away.
Turns out, the sensor washer positioned the electrode @ ~180deg from the original position = contact with piston !!