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ET: Engine (Twin) Spark Plugs

G.L. Winter

Website User
VOC Member
What are the most suitable spark plugs for a standard B model Rapide which is used at leisurely speeds in a small village and country lanes?
 

kettlrj

Well Known and Active Website User
VOC Member
I use Denso W22ES-U plugs on my 'B' Rapide. They are fired by magneto. I set the spark gap at 12 thou. The bike starts easily and runs well with these plugs.
The engine runs with 8:1 compression ratio, Mk2 cams and 1 3/16" TT9 carbs.
Regards Richard.
 

Attachments

ClassicBiker

Well Known and Active Website User
VOC Member
KLG FE70 if you can get them, sometimes they turn up, if you see them purchase them, better than anything currently produced.
A quick fleabay search will usually turn up some new old stock. But as with anything check the prices carefully. I've noticed some vendors will offer them at low prices but the shipping cost seems to be for a private courier with armed guards. There is a vendor near me who has been asking for $20 for a FE50 and $20 for shipping, totally ridiculous. The two below I found by searching KLG FE70. I usually query "KLG Spark" then spend a little time going through them. Skipping those that are obviously not what I'm after, but double checking those that aren't entirely clear as to what they are. Those that list by the car they fit are a good bet for being reasonably priced. Don't discount those that can be taken be taken apart (detachable) and cleaned "DFE70". It's the same plug.
Doing this I've managed to amass a small stash for my Vins, Triumphs, and MG B without breaking the bank.


 

Gary Gittleson

Well Known and Active Website User
VOC Member
I've been using NGK BP6ES for the last three years. They're supposed to be slightly hotter than the FE80 but at least in my case, the plugs are running a bit on the cool side. Otherwise, the NGK's seem fine to me.

So what wonders would I experience by switching to KLG? I did use them in my Norton Atlas all those decades ago. They seemed to work well enough although that Atlas was a beast to start at times. I guess I didn't know enough and/or didn't have enough money to correct the situation back then. The problems were probably in the mag and/or carbs. Compression was fine, as the bruises to my right shin were able to attest.
 

peter holmes

Well Known and Active Website User
VOC Member
It would be hard for me to tell what wonders might await you if you were to try KLG FE70 spark plugs, probably nothing spectacular, all I can tell you is that they quite simply work for me, I have tried most of the others, NGK, Champion, Nippon Denso, Bosch, etc. and the KLGs seem to work best, they start easier, seem more reliable, and last longer, if I feel the starting performance is going off a bit I give them a quick clean and away they go again, I have a few in reserve and calculate that they will probably see me out, unlike the aforementioned other brands would be likely to manage.
 

Sakura

Well Known and Active Website User
VOC Member
It seems unlikely to me that old technology like the KLG FE70 is the answer for every Vincent, and I don't think anyone is suggesting they are. Unlike modern bikes which are basically identical, in each model, every Vincent is now pretty unique, as has been attested many, many times. Therefore most Vincents will "prefer" a particular plug. One size does not fit all.
 

vibrac

Well Known and Active Website User
VOC Member
I think in previous iterations on here of this subject its been said that the previous status of NGK being the premium modern plug has taken a dive due to the claim that modern cars with black boxes dont get rich mixtures and so NGK have lowered the capacity of the plug to withstand rich mixtures by reducing the ceramic coating processes that were needed by carburetor engines. And it seems that contrary to the received knowledge of most of my automotive years the dreaded Champion plug has gained ascendancy. That may be true But I must agree nothing looks better than a racing FE75 KLG with a red (pink?)insulator you can just see it peeping out of my spare plug ole' behind my steering damper on the Flash

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G.L. Winter

Website User
VOC Member
Thank you, Stu, for your suggestion. I happen to have some N9YC plugs on hand, and so shall try them. The KLG FE80 plugs I have been running seem a bit too cold for my decidedly relaxed sort of riding.
 

Albervin

Well Known and Active Website User
VOC Member
Plugs and oils. Great sources of discussion. I always ran my old C Comet on an NGK B6 something. No problems. I then bought my Rapide and did the same. Also no problem. Then I lashed out and bought a stack of British plugs from the Green Spark Plug Company. Not exactly a waste of money but close. It is important to know your NGK plugs are Made in Japan. I can lean on my kick starter and the bike fires up. I have no idea how old those plugs are.Specs are pretty much standard Series B Rapide; magneto, no high comp, no high lift no big carbs.
 

peter holmes

Well Known and Active Website User
VOC Member
It seems unlikely to me that old technology like the KLG FE70 is the answer for every Vincent, and I don't think anyone is suggesting they are. Unlike modern bikes which are basically identical, in each model, every Vincent is now pretty unique, as has been attested many, many times. Therefore most Vincents will "prefer" a particular plug. One size does not fit all.
Well yes and no, it is true there are endless possibilities to modify a Vincent to "make it better" but the environment that the spark plug operates in, the combustion chamber, is not so easy to change from the original specification, 8-1 compression ratio seems to be about all you need, a spark is delivered by whatever means and jumps across a gap, the ratio between fuel and air should be about the same whatever device is being used, the fuel is rubbish compared to days gone by, but should still ignite, none of that explains why KLG plugs work the best for me, but they do.
 

oexing

Well Known and Active Website User
VOC Member
Spark plug discussions are endless most times, in all forums, and people tend to advertise certain brands religiously. But fact is you have to choose the suitable grade in any brand for YOUR style of driving. Get this wrong and you end with all sorts of troubles - but most will find black plugs today by picking the famous racing grades although they baby their engines. In consequence the plugs not nearly get that temperature to burn clean. Sorry, get a "touring" grade plug and you´ll live happy ever after and brand is no factor at all.

Vic
 

kerry

Well Known and Active Website User
VOC Member
Interesting information posts BUT BEWARE , I have had a box of 'fake' denso plugs from eBay that caused me terrible problems and they actually looked better than genuine ones, apparently there are also duff NGK ones about, I must say I only buy plugs now on eBay from the green spark plug co, In my D I have been using Champion N4C Not sure if they are correct though ? I will be looking out for FE70 like everyone else I guess
Kerry.
 

Nulli Secundus

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I have also bought what I believe are fake Champions for my Commando from a very well known UK Norton parts supplier/specialist. I ignored advice and went to NGK after that, which is the brand I also use in my 1938 Rudge race bike.
 

kerry

Well Known and Active Website User
VOC Member
I know my denso were fake, from a box of 10 5 failed within about 10 - 20 miles, I didn't know there were fake champions about, someone suggested 'brisk' spark plugs are easily the best but I don't know if they make them for Vincents, they are a modern plug for older engines etc ??
 

oexing

Well Known and Active Website User
VOC Member
I wonder how all those "fake spark plugs" looked when replaced. My guess: Black. Has anybody sand blasted these and tested again ? I have never come across fake plugs in decades and believe you just picked a too hot type for your pottering around these times. Does not help to have same types in the engine like you had when you were a few days younger - and a bit more dedicated on the throttle . . . . .

Vic
 

kerry

Well Known and Active Website User
VOC Member
They were not black, they were faulty and that was agreed with a Denso representative, attached shows both genuine and fake, ironically the fake looked better but failed promptly, examples of fake NGK are also online for your perusal.
 

Attachments

ClassicBiker

Well Known and Active Website User
VOC Member
A few years back I was helping the stepson of my friend work on his Honda 900. The stepson received a brand new set of plugs, NGK, from his father. The father had acquired them from a friend of his who owned a parts store of some description. They appeared brand new and genuine. We could not get the bike to start at all. So we replaced the new plugs with the old beat up Champions. It fired up no problem. We got curious if the failure to start was because of one or all plugs. So our plan was to replace only on Champion at a time with a NGK. With three Champion and one NGK the engine ran like rubbish. So we swapped that bad NGK out for another NGK. Same result. The remaining two NGK plugs were no different.
I don't think it was an NGK quality problem, as I know people who use NGKs with not issues. I believe they were knock offs from counterfeiters. Understandably retailers look to buy from the least expensive wholesale distributor source. The wholesale distributors purchase from the manufactures, one would hope, so I don't understand how the counterfeits make it into the supply chain. I would hate to think the distributors were knowingly filtering the counterfeits into the system for the sake of profit or that the retailers were knowingly buying them from a questionable sources for the same reason.
I'm sure the problem is not just limited to spark plugs, either.
Steven
 

oexing

Well Known and Active Website User
VOC Member
Steven, thanks for sharing your troubles with NGK plugs in the forum. Seems fakes are a real factor with famous brands but I would not have believed that modest price items like spark plugs were attractive for fakers. When fabricating fake plugs there are quite some costs of investments to start production so one could produce working spares as well with no practical extra costs - or so I´d think. I have always had Bosch plugs since I was a boy as they have the nickel plated steel sections for nice shiny durable finish. With good luck Bosch seem unattractive for fakers as I never had defects as described. Basically a spark plug is no complicated item so should be reliable in operation. Some or most types have an inbuilt resistor for less radio emittance or limiting current from coils. I seem to remember that resistor plugs were not recommended for magneto ignition with poor mag types . A faulty resistor may be tested with a multimeter and in doubt the plug be scrapped. Anybody with a fake NGK for testing this ?? To be honest, I am now curious to get a fake for looking inside to learn what can be wrong with these. In most cases I only had fouled plugs in need for cleaning due to wrong grade choice.

Vic
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