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What are your thoughts on Spark Plugs for a Twin?

BlackLightning998

Well Known and Active Website User
VOC Member
Evening all,

As you may note from my thread on Carb problems I am currently suffering an annoying problem on the front cylinder of my twin, as yet unidentified but looks like it is either carb problem (running rich) or oiling problem to the front cylinder - too much of it in the bit that burns the fuel!!

Anyway - I have gone back to a Champion N5C from the NGK B7 that I was using.

I wondered what the "weapon of choice" is for the Twin these days - I found this information below on Iridium Plugs and wondered if these are something that VOC members have tried?

Look forward to comments and recommendations.

Cheers

Stuart


"Iridium spark plug specifications and benefits
Relatively recent advances in fabrication techniques have enabled the use of Iridium - an incredibly hard precious metal, for the construction of spark plug electrodes. Laser technology is used to weld the Iridium tip to spark plugs manufactured by both Denso and NGK. It's worth noting that spark plugs can't increase the potential power that an engine can generate but a more efficient spark will provide more efficient combustion and associated performance and economy benefits. A poor spark from a worn or low grade spark plug will reduce efficiency. An Iridium plug will produce a more efficient spark. Notable properties of Iridium are its melting point - approximately 2450 degrees C, considerably higher than Platinum, and it's strength - approximately 8 times that of platinum. The table below compares the characteristics of Iridium with those of other precious/semi-precious metals commonly used in the construction of spark plugs.
There are currently two main manufacturers of Iridium spark plugs for automotive use available in the UK. NGK produce a product range known as Iridium IX and Denso produce Iridium Power spark plugs. Both are very high quality products using laser welding technology and manufacturing techniques perfected over a very long history of spark plug design and manufacture. Both manufacturers also manufacture OEM Iridium plugs, installed in some vehicles at the factory and usually having Iridium centre electrode and platinum chipped ground. Where an OEM Iridium plug is specified there is little to be gained by changing to an Iridium IX or Iridium Power plug. Champion have manufactured Iridium plugs for use in large industrial engines for quite some time but have not yet put any automotive parts into production.
Advantages of Iridium spark plug types
Due to the properties of Iridium, the spark plugs centre electrode can be made with a much smaller diameter than with platinum, Gold or gold palladium and copper/nickel types without sacrificing service life. The spark plugs potential difference is more concentrated at the tiny Iridium tip and hence less 'spark jump' voltage is required - this can be as much as 5,000 volts less than with standard plug types. Ignition is improved and less strain is placed on the ignition system. Benefits of improved ignition/combustion include better fuel economy, increased power/acceleration and especially better throttle response."
 

greg burt

Well Known and Active Website User
Non-VOC Member
S/Plugs

Stuart
This subject had a big airing on jtan.
BPR5EIX NGK Iridium - I used these in both my twins with standard magneto's and had NO problems -1st time starters at all times / Some people think you should not use resistor plugs with a Magneto - Resistor caps were used in the 50's for telecommunication interference.
B =14mm thread - 20.8 mm hexagon
P = projected insulator nose
R = resistor type
5 = heat rating number
E = thread reach - 19mm
I =iridium
X = series gap

I use these in my Rapide:
Bosch - W6DPO Platinum = 6 Heat rating in NGK
W= 14mm thread - 20.8 mm hexagon
6=heat rating number
D= thread reach -19mm
P= Platinum
O=Deviations from basic version - Earth Electrode comes in from the side.

Black Shadow
Bosch W8DP
W= 14mm thread - 20.8 mm hexagon
8 = heat rating number =5 heat rating in NGK
D= thread reach -19mm
P= Platinum

20 thou gap for standard Magneto / I went to 5's to eliminate sooty plugs - both my bike plugs run perfect' also I think having the nose in the flame front helps.
Iridium NGK also claim to have a (after charge)to help burn off to keep the plug clean.
I gather you have Electronic Ignition (pazon- I dont know anything about)
Does this system need a Resistor cap or Plug for magnetic field interference ?
Whatever Plugs you use the Ignition system needs to be healthy (Delivering a good Spark)
Hope this Helps regards Greg
 

BlackLightning998

Well Known and Active Website User
VOC Member
Spark Plug Advice

Thanks Greg - very helpful.

I will have a read through FYO, ATY to see if I can find any more advice on plugs to read.

Your experiences are helpful too - I may well add some of your plugs to my selection for trying.

I don't think there is a "search" function on JTAN for getting access to old threads is there?

PAZON are recommending Denso platinum plugs for their ignition system and the advice I am getting here in the UK from a Spark Plug specialist is:

"Denso ZU platinum options would be W20EP-ZU (projected) or W20ES-ZU (non projected), these are non resistorised plugs. You may be able to use an Iridium plug with your electronic ignition, perhaps Denso IW20 (projected).

If you are persistently fouling plugs the problem is more likely to be carburation but you may be able to work around the problem with a warmer plug, IW16 or W16EP-ZU. N5C is a non projected plug and therefore will have the effect of running a little cooler than BP6ES for instance"


I'm thinking of buying and trying the Denso W20EP-ZU and the Denso W16EP-ZU and wondered if any Forum members had experience of either plug in a Vincent Twin?

See my thread on the carb's to read the "latest instalment" of me trying to get my bike running properly again.......

Regards

Stuart
 

Henry Martini

Well Known and Active Website User
Non-VOC Member
Hi Stewart,
I am running my twin with Pazon ignition. I was using BP6ES but now am using DENSO IRIDIUM IW22 no problems all Iridium plugs have built in resistors
so I use a plain no resistor plug cap I did run the Denso's with resistor plug caps but the Pazon ign systenm did not like that.I have used the Pazon system since the Canadian International 5 or more years ago never any problems. I did however find that using the recomended MK2 carb jets and settings the plugs were always very black and needed frequent cleaning or replacement. In the last year I have spent much time on leaning the mixture
am now running smaller main jets 4 1/2 slides and It now runs smoother and faster then it ever did the plug colour is now almost right and I get 60 miles to the gallon at a steady 60/70 mph and 48 to the gallon at a steady 80/85 mph I belive it is still running on the rich side of correct. I can't remember the main jet size but if you want I will check it out.

The best to all
Henry
 

BlackLightning998

Well Known and Active Website User
VOC Member
Henry - that's really helpful - yes please?

Hi Henry,

Much appreciated, it's nice to make contact with someone running Pazon ignition as it makes a few comparisons easier and perhaps more relevant - very interesting to read of the adjustments you have made.

My bike is running non-original 276's with bolt on flange, though I would imagine this won't make a material difference once you get inside and start chatting about needle position, needle size, slide cutaway and jet's sizing - so yes please I would be very interested to learn what sizes you have in there now? (I'm sure you will have seen my thread running on trying to sort out my carbs too).

Look forward to hearing from you.

Regards

Stuart

Hi Stewart,
I am running my twin with Pazon ignition. I was using BP6ES but now am using DENSO IRIDIUM IW22 no problems all Iridium plugs have built in resistors
so I use a plain no resistor plug cap I did run the Denso's with resistor plug caps but the Pazon ign systenm did not like that.I have used the Pazon system since the Canadian International 5 or more years ago never any problems. I did however find that using the recomended MK2 carb jets and settings the plugs were always very black and needed frequent cleaning or replacement. In the last year I have spent much time on leaning the mixture
am now running smaller main jets 4 1/2 slides and It now runs smoother and faster then it ever did the plug colour is now almost right and I get 60 miles to the gallon at a steady 60/70 mph and 48 to the gallon at a steady 80/85 mph I belive it is still running on the rich side of correct. I can't remember the main jet size but if you want I will check it out.

The best to all
Henry
 

Henry Martini

Well Known and Active Website User
Non-VOC Member
My carb settings

OK Stewart, looked inside my carbs to day the settings are :
32mm Mk 2 carbs with K&N air filters, main jet 190,nedle jet 106, nedle 2A1 set on middle slot,Pilot jet 20 fitted in float bowl,Slide 4 1/2, Pilot air screw 1 1/2 turns out. Pazon Smart Fire Ignition with 36 deg fully advanced.
These settings are very close to ideal for my bike. I was running 240 main jets, far to rich as I belive are most bikes. I came to the above settings over a period of time reducing main sizes one jet size at a time. I found that changing main jets had a effect on the nedle jet and other settings so as all the books say first get the main right first.I advise caution it is better to have a slightly rich setting than a expensive hole in your piston.By far the best and fastest way to get it right is on a roling road, but you need to find a operator who understands our form of carburation. most only know how to change map settings on on modern electronic fuel management systems.
I hope this info is of some help to others.

Best regards to all,
Henry Martini
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Plug ratings

This is the second thread I've read recently (the other was jtan and may be the same people) which sought to cure plug fouling by going to iridium plugs. I have no feelings about iridium either way, but in each case the plug that fouled was an NGK 7. This is far too hard (cold) for a Vincent unless to some extreme level of tune - an AJS 7R or 350 Manx runs on an NGK 8. NGK BP6 is actually NGK's recommendation for a Vincent twin (I have an obsolete NGK publication that covers Vincents, Rudges and Sunbeams among many others). I've also used 5's to mitigate oiling symptoms, like an enforced plug change every 150 miles. The disease was cured by fitting new pistons and valve guides - whereupon the symptoms disappeared and I could go back to a 6 in the front. However for 6000 miles before I bit the bullet I ran a 5 in the (offending) front and 6 in the rear and while the 5 looked less like a plug and more like a slag heap when examined, never actually stopped firing.
 

BlackLightning998

Well Known and Active Website User
VOC Member
I did 150 miles today....

Evening all,

Yes Tom - I tried JTAN too as I've learnt there are many people there who won't use the Forum.

I put the Denso W20EP-ZU in and did 150 miles today on the needle dropped one notch and the carb cleaned thoroughly.

She is still running very sooty - but ran perfectly well on the run, happy to sit at 30mph on a back road and tootle along, equally at home pulling strongly up a slight gradient through 90mph and beyond very enthusiastically. Very happy at 50-60 in top all day long. Front cylinder did not miss a beat.

I think I will now get hold of some Denso W16EP-ZU (which will run slightly hotter) and see if that helps things get better still.

Looks like I might do the Riders Rally after all.

Thanks to all for suport so far - I'll post more detail on my carb thread - I think changing down the 170 main jet is next on the list.

Regards

Stuart

This is the second thread I've read recently (the other was jtan and may be the same people) which sought to cure plug fouling by going to iridium plugs. I have no feelings about iridium either way, but in each case the plug that fouled was an NGK 7. This is far too hard (cold) for a Vincent unless to some extreme level of tune - an AJS 7R or 350 Manx runs on an NGK 8. NGK BP6 is actually NGK's recommendation for a Vincent twin (I have an obsolete NGK publication that covers Vincents, Rudges and Sunbeams among many others). I've also used 5's to mitigate oiling symptoms, like an enforced plug change every 150 miles. The disease was cured by fitting new pistons and valve guides - whereupon the symptoms disappeared and I could go back to a 6 in the front. However for 6000 miles before I bit the bullet I ran a 5 in the (offending) front and 6 in the rear and while the 5 looked less like a plug and more like a slag heap when examined, never actually stopped firing.
 

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