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Triumph 3HW spark plug

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Personally I don't like NGK and for years I've used Champion L82C in my OHV engines (L86C in SV's)

But lately I'm going over to Bosch W7AC in my OHV's  (W8AC in SV's)

I was periodically having to change the Champion plug in the rear cylinder of my Indian Special after it would foul up and fail. There is a slight over oiling problem on the cylinder which I'll look into one day, but changing to the Bosch grade which I researched has dramatically decreased the failure rate.

They're only about £2 each inc post from Tim Green so worth buying  some of each make to try for yourself.

https://www.gsparkplug.com/

 

Ron

 

Edited by Ron

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Thanks Ron, 

I too have fallen out of bed with NGKs and have been using Denso Iridiums in my Jap bikes.

 I just couldn’t find out any info online for the correct model of plug 😀.

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I don't think the Iridium's are any good in a magneto bike, but I tried them in my special (coil ign) and despite the huge extra cost didn't really find any benefit.  It seems ironic to be putting a German plug in these bikes, but it wouldn't surprise me if they're all made in China anyway!  But for about a tenner you can buy 5 plugs, say 3 Bosch and 2 Champion or vice versa and keep some with the bike for trial. Ron

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I was wondering about magneto and iridium plugs, I’ll just get normal ones then, all my jap bikes have electronic ignition.

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Yes Magnetos don't like plugs with any form of built in suppressor or even suppressor caps for that matter. Just plug the lead straight on with a spade terminal or a non suppressed plastic/Bakelite cap .

The spade terminals and knurled nuts and non suppressed caps are also available from Tim Green.  Ron

3HW 203.jpg

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Thanks Ron, 

I’ll go with Champion, I can’t bring myself to put a german plug on a British bike 😃.

Edited by HotBed

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4 hours ago, Ron said:

Yes Magnetos don't like plugs with any form of built in suppressor or even suppressor caps for that matter. Just plug the lead straight on with a spade terminal or a non suppressed plastic/Bakelite cap .

The spade terminals and knurled nuts and non suppressed caps are also available from Tim Green.  Ron

3HW 203.jpg

hi Ron,

When riding my WM20, I used a lawn mower suppressor cap as it is of lower Ohms rating than a normal vehicle ones, think from memory, 5000 against 15000. Never had any problems and I did high mileages with it. It was against the law to have an un-suppressed vehicle as I can remember having the radio or TV on and an old motorcycle passed by, you could hear every gear change on the interference received!

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Yes Richard they will of course work with a suppressor and most bikes would have had one fitted as I guess that Wireless suppression was far more important than any adverse effect it would have had on the mags life or its ability at the best spark. 

The HT leads were often quite busy things back then, as in the case of some bikes, they were fitted with a Lodge or KLG non suppressed Bakelite cap, an in line suppressor and a rubber covered immobilizer. If I fit a suppressor "for appearance sake", I drill out the innards and slide it on the lead and glue it on with clear silicon.   Ron 

WDL-G 118.jpg

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The incorporation of resistance in an HT lead is not just beneficial for RFI suppression but it helps curb the rate of erosion on the plug electrode. The current flow is very small & the introduction of a seemingly high resistance into the circuit results in a drop of only tens of volts which is minimal with an HT of thousands of volts.

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OK Clive I'll put that to my magneto guy. Maybe it's a myth, but the magneto guys I've dealt with over the years and other guys, supposedly in the know, are adamant about not using a suppressor??  Ron

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Ron I have no experience of magnetos my observations are just based on vehicle ignition. I think I measured the current flow in a typical ignition system whilst running was 7ma.  I think that equated to a drop of 10v in an HT of about 7kV in a suppressed lead or lead with a suppressor.

Over the years I often heard of people advising that suppressed leads should be removed & copper used & to use no  suppressors. But I think some of that sprung from problems of resistive cables failing & in particular the termination of the inner conductor.

I wouldn't have thought a magneto system would require a higher current as that would only increase electrode erosion, we all know higher current on a welder melts metal faster.

As an aside at most shows I operate an amateur radio station on 50, 70 & 144 MHz on the lower two bands RFI is pretty extension & on some occasions wiping out quite strong signals. This interference can be homed in on with the yagi antenna long before I can hear or see the offending vehicle. So sometimes wonder if the ignitions systems are run with minimal suppression in belief of improved performance or whether the vehicles are being run to the original wartime spec.

If it is the latter I would have thought it would have been  an issue for wireless communication within a unit. Also no amount of camouflage or stealthy driving can disguise the onset of a vehicle up to a quarter of a mile away. I know this because I am in a radio group at WPR adjacent to the main road where I could detect on coming vehicles & then view them disappear along the main road. Given their speed I estimate that they could still be detected up to a quarter of a mile away with a directional antenna.

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Ah you had me worried Clive. Yes we are talking Magnetos here. I just received this back from my guy who has been restoring all era magnetos for 40-50 years. Ron

 

Hi Ron,

Yes you are correct.

I read an article from the US Army Air Corps years ago,  the article probably from the hey day of magnetos in the 1920s said it was bad news to use suppressors or spark intensifiers on magnetos.  I believe the Americans.  It's complete combustion that you want.  

Cheers,

Chris

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That's an interesting link thank you.

I see that the spark gap is quite large on a magneto ignition compared with distributor ignition & the current is much higher as well.

Maybe the erosion rate is shared on a 3-point plug? Do plugs wear out more rapidly than in a distributor system, although I suppose perhaps they do as a vehicle  may have 4 or more plugs to share the work which is at a lower current?

That would explain why m/cycles seem to be the most generous of the producers of RFI. I didn't say that before in case it looked unduly rude. Anyway Ron that was an interesting lesson learned, thank you.

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Yes Clive it's all worthwhile discussion. You mention a 3 point plug. It is erroneous to assume that multiples of the electrodes spark together. Only the electrode with the best conditions (Gap etc) will spark. Just the same as any plug. It's just that the spark has a choice of route. Ron

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Ron yes its good to talk about these things & explore the subject.

This is not to argue but to explore a bit further. But is there only one spark on a 3-point plug? This is a picture I took of a fouled up plug & there were several of them at it!

 

Dsc04318x.jpg

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What sort of plug is that, Clive ? The pre-war KLGs had a single centre electrode and three adjustable. Received wisdom is that, certainly on worn engines,  with only the closest sparking, there was a tendency for the other two to foul up until they eventually shorted out.  This may have been more true of two-strokes or really worn oily engines.

Motorcycles were always bad for RF interference, even when in good condition. Is it because there is no screening from bodywork ? Japanese motorcycles had tin-plate clad suppressed caps but if it rained then they gave a display like the Aurora Borealis so we always took the cladding off !

 

 

PB161009.JPG

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The plug is a RSN13P a screened plug with a single side platinum electrode. The plug is so fouled that there is no spark across the official gap!

Do some aircraft plugs have 3 electrodes? I wonder how they behave or meant to behave?

Then to tilt the topic even more I have a BIOS report of the German WW2 development of sparking plugs for use at high altitudes with an HT of only 700v !

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