Spark plug failures

[Boxprod]

Does anybody have experience of buying a plug from an apparently reputable supplier, only to have it fail within a few running hours?

I bought a couple of NGK B7HS plugs from Am*z*n, which certainly look genuine, and were a sensible price (not ridiculously cheap, in other words), but I've had two of them fail within only a few miles.

They are fine from cold in my '74 350 widecase, and the engine runs very well now I've sorted out the carburettor jetting etc., but trying to restart it when hot is a nightmare.

I thought it must have been my fiddling with the jets, but I found that I was getting little or no spark at kick-starting speed with the hot plug. Change the plug, and bingo! Loads of spark, even with the plug that had previously failed this test and been left on the bench for a day or two.

So it looks as if the "NGK" plugs are either being built to a less than adequate standard, or else the prevalence of fakes has suckered even the canniest retailer on the planet. What I have seems to break down when hot, although they also recover after cooling down!

Tomorrow I shall do two things. First I shall go to my local motor factor and try to buy a Bosch equivalent (not quite so popular, so less likely to be faked...?), and then I shall talk to F2 Motorcycles in Wisbech about Brisk plugs, which are made in the Czech republic, and get a very good press.

And I shall let you know how I get on. In the meantime, I know that the sort of aerobic exercise one gets in trying to start a hot and reluctant engine is probably very good for the elderly.

Onwards and upwards,

Pete.

[themoudie]

Aye Pete,

So far I have yet to come across a duff NGK spark plug. I purchased them from either my Halfrauds local branch, or my local motor factor, via a local motorcycle repairers trade account. I used to also use Champion spark plugs in the 450, but found that the electrodes appeared to erode more rapidly than the NGK. Champion plugs in the Honda Bros and the SRX 600's also tended to erode or carbon up, inspite of being the Champion recommended heat range. Changing plugs in the Bros, especially the nearside front cylinder plug, is a tortious exercise and on a SRX involves fuel tank removal and soaking in PlusGas 'A' and blowing out the accumulated road grit from around the plug seat, before attempting to shift the blighter and not drop grit down the hole! NGK plugs appeared to enable the engine to start more easily and reliably tick-over than the Champion equivalent.

Only ever used Bosch spark plugs in Stihl/Husqavarna chainsaws and they were always more prone to oiling/whiskering than NGK plugs. Hence, a preference for NGK plugs.

I too have seen the 'Brisk' spark plugs marketed by F2 Motorcycles and would consider giving them a trial, not only in the 450, but also in the rest of the fleet, as servicing requires.

I shall be interested to learn of your experiences, if you should choose to give the 'Brisk' plugs a trial.

Good health, BillR

[graeme]

Pete,
Look at the NGK site explains how to pick Chinese copies.
Beware

[Duccout]

Hi Pete,

Apparently this is a major problem; a few months ago I did some research after hearing about this problem and it looks like buying any NGK plug is risky. I was lucky and found someone on eBay selling some new old stock ones and bought a few, but as for buying brand new ones.... The same problem is affecting Mitutoyo digital calipers, where apparently the fakes are indistinguishable from the genuine article. Funny times.

Cheers,

Colin

[Boxprod]

Thanks to all for the advice - an example of the experience and generosity of this forum!

As I wander down the rabbit holes dug around our wonderful and maddening old bikes, I try to remember that any faults are likely to be caused by the simple things... so rather than start taking everything apart down to the stator, I shall indeed change the plug and see how I get on.

One thing I don't quite understand about fake components of any sort is that they surely cost quite a bit to make no matter how low their actual quality. I mean, a plug is hardly a high-value product at less than a fiver a pop, and you would need a pretty good manufacturing setup to make them at all, so the fakers must be able to make them VERY cheaply and shift a ton of them in order to "succeed" at their business. And that takes a lot of hard graft and expense to make a convincing fake.

Could it be that like branded clothing made in far-distant countries, the "genuine" items come out of the front door of the mill, while the "fakes" simply come out of the back door of the same mill? (Example: Lacoste polo shirts with the crocodile logo pointing the wrong way.)

That's enough rambling.

Pete.

[blethermaskite]

Hi Pete,
Generally I prefer NGK plugs, however a couple of times ( I think) I may have got a fake/dud. But.....I have another question for you, is your 74 widecase 350 (that's what I have as well) running on motoplat electronic ignition?.....your spark plug failures sound exactly like the behavior of my 74 350 about 15 years ago as the motoplat system slowly failed to be replaced with a Lucas Rita system.
Just a thought.
Cheers, George

[Boxprod]

Dear George,

Yes I'm still running on Motoplat, but my entire system has been given some magic dust by Steve at Bradford Ignitions (which happens to be not far from me here in Cornwall). Website here: https://uk-motoplat.com/

I had him do two stators and check three CDI units. He dug the potting compound off the ignition coil and rewound that, with 25% more wire so giving a much fatter spark, and renewed all the output cables, then replaced the potting compound by hand (not pretty, but it works). The CDI unit I'm using at the moment came from a square-four racing Yamaha (?RG500), so they are pretty robust bits of kit, and Steve has confirmed that it's fine - in his experience they either work or they don't.

So I'm pretty confident that all is well with the Motoplat side of things. And I've got enough spares if something really has gone phut.

Fingers firmly crossed...

Pete.

[ranton_rambler]

Brisk plugs are mentioned further up this thread. This is by no means a scientific appraisal, but my pre-war Rudge was terrible when using both NGK and Champion plugs. There is no oil control ring on the Rudge piston, so they are a bit smoky at the best of times. And the Maglita ignition doesn't make the biggest sparks. I was recommended to switch to Brisk as they are apparently made the old-fashioned way with glazed insulators. Most modern plugs are unglazed as modern engines are so clean burning, and therefore absorb oil and unburnt fuel and stop working.

In the Rudge, the Brisk plugs have worked well and as they are the same grade as my Ducati 175 uses (Brisk N15 = NGK B6HS) I thought I would standardise both bikes to Brisk. The Ducati really didn't like the Brisk plugs, so I have gone back to NGK bought from a reputable source. It has standard coil & points ignition except for conversion to 12V.

Ian P

[Boxprod]

Dear Ian,
Your Rudge obviously knows a thing or two!
I've just done a relatively energetic ride of 160 miles each way to see my son (who is the proud owner of a modern 650 Continental - nice bike, as far as I can see so far). The roads are a mixture of fast dual-carriageway and sensible A roads, and I'm delighted to say that nothing fell off either the bike or the rider.
The Brisk spark plug did exactly what we all expect, without a single miss, so they get my vote.
Geared for what my arithmetic tells me is just under 14 mph per 1,000 revs in top gear, cruising at the legal limit (honest, officer) of 70 mph is just over 5,000 rpm, and I found I could keep it up for as long as I could manage the riding position (rearsets and clip-ons, but with the benefit of a half-fairing).
So Brisk plugs do the job as well as all our old memories of KLG, Lodge and Champion. I may ask the importer for a commission.
Happy autumn, everyone.
Pete.

[Jordan]

To help diagnose, you could try a cheap CDI coil made for scooters.
I have used one of these for some years now on my 350.
https://www.ebay.co.uk/itm/285299749657