E: Engine Ignition Advance

oexing

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My guess, most troubles motorists have with spark plugs are just a consequence of picking the unsuitable grade of plugs. When deciding on grades you don´t want to go for racing types as is state of the art in Indianapolis but instead you really look at YOUR style of riding. This will be the factor to get the sutable grade and the brand will not be essential. Otherwise the "bad" brand would have been in real troubles for selling "bad" products for ages. A Vincent engine is not different from other gasoline types in this respect - apart from having crap magnetos for ignition often enough.

Vic
 

Simon Dinsdale

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Knowing something about high voltage gas and vacuum switches and ceramic insulators having worked on them for years I think it's down to the ceramic insulator material used today. Now taking that knowledge and looking at a spark plug I have a theory about what's happening but I no longer have access to stuff like electron microscopes to look for contamination of a cross-section of the ceramic surface etc.

Basically spark plug manufacturers today make plug down to a cost and so have a manufacturing process that produces plugs that suit modern computer-controlled injection electronic ignition where they can start an engine cold without using a rich mixture and so reduce the emissions. The upshot of this is the spark plug never sees anything like the rich mixture seen in our old engines and so the spark plug manufacturer can use a lower cost ceramic which I suspect has a coarser grain structure. I don't know if spark plugs 50 years ago had glazed ceramic insulators but looking at new plugs today they don't appear to be glazed. Now these modern plugs appear to fowl easier with a rich mixture and once that occurs the plug is scrap and this is what we are seeing with modern plugs in our old engines fed via carbs. I have taken such a fouled spark plug and tried to even bead blast them clean and they still won't work so the contamination has penetrated the grain structure of the ceramic surface and is not simply sat on the top of the surface.

Please note this is all just a theory, but after suffering problems with Champion plugs in my Vincent, but not in modern cars, I have found Denso Spark plugs to be one of the better ones for older designed engines and have used in my Vincent the Denso W20EP-U for the last 15 years and the last one I changed was as 20,000 miles and still working fine. I have stocked up with enough so I will never have to buy a spark plug for one of my bikes ever again, but beware and always buy from a known source as yes there are fake plugs out there, probably made in China.

Just realised I probably started a panic buy on Denso plugs, but at least it different from panic buying toilet rolls"

Simon
 
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greg brillus

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Simon I would say you are most likely correct........Plugs can be a pain.......I would say the main thing is to have an engine that is in a well enough state of tune that the plugs run well enough to not give trouble........And that should be the case. Of course that is easy for me to say, given I am a mechanic, and play around with these things every day. So basically if your engine is burning excess amounts of oil or the carburetion is too rich, then yes plug failures will be a common problem........Like our modern fuels, we have to live with it all.........An engine old or new that is tuned up well enough will run happily and not fowl plugs regularly.......
 

highbury731

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Is the Green Spark Plug Co a safe supplier?

I tried their site for the Denso W20EP-U - they list it for £1.70 inc VAT. Seems cheap to me

Also, I read that they are factory set to a plug gap of around 1mm / .040" ish, and are delicate wires. Can they be set to small clearances for our poxy magnetos?

Paul
 
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oexing

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These days many spark plugs have an internal resistor at 5 kOhm to fight radio emissions. In case of crappy mags that type may not be the best idea so go for plugs with no resistor, possibly this being the cause for some troubles today. So not really a question of brands, more like wrong grade or resistor. On some plugs an R in the code may show the resistor kind.

Vic
 

Simon Dinsdale

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VOC Member
VOC Forum Moderator
Is the Green Spark Plug Co a safe supplier?

I tried their site for the Denso W20EP-U - they list it for £1.70 inc VAT. Seems cheap to me

Also, I read that they are factory set to a plug gap of around 1mm / .040" ish, and are delicate wires. Can they be set to small clearances for our poxy magnetos?

Paul
Thats where I get them from. Yes they are cheap as they are the Denso std non fancy range and contain no exotic electrodes.

They are a std copper / nickel plug with no resistor and don't have any fancy narrow electrodes made of unobtanium etc so don't I know what you mean by delicate wires. Yes you can easily alter the gap to suit you ignition and they run fine on coil ignition and Lucas magneto as I have used them with both ignition types.
 

LoneStar

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I've used Denso plugs with success - but on the other hand, never had any issues with NGK even though I flood the bike sometimes due to over-tickling.

Denso (and others) made non-resistor plugs with platinum fine-wire electrodes. These fire at lower voltage than plugs with larger, standard electrodes - helpful with a magneto that may be less powerful than when new. In any case, magneto voltage is proportional to RPM - a disadvantage compared to coil ignition when kick-starting.

Denso platinum plugs that will fit the Vincent are WxxEP-ZU, where xx is the heat range. 20, 22 & 24 correspond with NGK 6, 7 & 8 heat ranges.
 

erik

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VOC Member
Maybe it is a Little bit interesting what I did whith the atd unit : I drilled a 5mm hole in the tufnol idler so when I insert a 5mm pinn the atd unit is blocked in full advanced Position .No flimsy wedges necessary which could Escape into the Timing chest.To my mind this makes life easier to find the correct firing Point. Regards Erik
 
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