Spark plugs (2016)

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The risk of to hot a plug is detonation, leading to major engine damage. Found this quote from John Healey of TIOC, guy probably knows as much about old British engines as anyone on the planet. The original post was about going to a hotter plug to stop oil fouling Note the comments on oil in the combustion chamber changing the gas/air ratio and the comment on going to a hotter than recommended plug to stop the oil fouling. It's your bike but if it was mine I would trust what Jim C and John H say and run the recommended plug. They have both earned their pipe and slippers many times over with decades of practical experience.

"Toughening a motor to detonation is more than raising the octane of the fuel you put in the tank. Especially since it is not always possible. You mentioned compression and the lower the compression the less the incoming charged is compressed the less the engine will be prone to detonation. Compressing the fuel/air mixture raises it temperature.

And controlling detonation is all about controlling heat:
- If the ambient air temperature increases the engine will be more prone to detonation.
- If the rings haven't seated, and thus have the ability to transfer heat out of the piston, the engine will be more prone to detonation.
- If you were talked into using modern thin rings that do not transfer enough heat your engine will be more prone to detonation.
- If the rings haven't seated and oil is getting in the combustion chamber you are lowering the octane of the incoming fuel/air your engine will be more prone to detonation.
- If you have a valve job where you were talked into a "performance" valve job with valve seats widths of .040" or less your engine will be more prone to detonation.
- If you are convinced that Triumph didn't know what they were doing when they determined the overall gearing in high gear and the engine rpm when doing highway speeds your engine will be more prone to detonation.
- If you are convinced that Triumph didn't know what they were doing when they suggest a spark plug your engine will be more prone to detonation.
- If you are selecting the grade of plug for fuel or oil fouling, instead of temperature your engine will be more prone to detonation.
- If you haven't removed all of the sharp edges on the piston and combustion chamber your engine will be more prone to detonation.
- If the valve margins are too thin, they will not cool properly your engine will be more prone to detonation.
- If you do anything to hinder the transfer of heat out of the cylinder and head fins your engine will be more prone to detonation.
- In places where the ambient air temperature exceeds 100° F being careful of riding style and monitoring oil temperature is something I would consider.

The ability to control heat is the limiting factor in what you can expect from one of these engines."
 
htown16 said:
The risk of to hot a plug is detonation, leading to major engine damage. Found this quote from John Healey of TIOC, guy probably knows as much about old British engines as anyone on the planet. The original post was about going to a hotter plug to stop oil fouling Note the comments on oil in the combustion chamber changing the gas/air ratio and the comment on going to a hotter than recommended plug to stop the oil fouling. It's your bike but if it was mine I would trust what Jim C and John H say and run the recommended plug. They have both earned their pipe and slippers many times over with decades of practical experience.-I put the N4Gs in today. Only some short runs with the BP6ES plugs, so risk was minimal.

"Toughening a motor to detonation is more than raising the octane of the fuel you put in the tank. Especially since it is not always possible. You mentioned compression and the lower the compression the less the incoming charged is compressed the less the engine will be prone to detonation. Compressing the fuel/air mixture raises it temperature.-So the guys running 87 are more at risk than those of us running 93.

And controlling detonation is all about controlling heat:
- If the ambient air temperature increases the engine will be more prone to detonation.- It does get hot here in August
- If the rings haven't seated, and thus have the ability to transfer heat out of the piston, the engine will be more prone to detonation.-They have
- If you were talked into using modern thin rings that do not transfer enough heat your engine will be more prone to detonation.-I wasn't
- If the rings haven't seated and oil is getting in the combustion chamber you are lowering the octane of the incoming fuel/air your engine will be more prone to detonation.
- If you have a valve job where you were talked into a "performance" valve job with valve seats widths of .040" or less your engine will be more prone to detonation.-Didn't happen
- If you are convinced that Triumph didn't know what they were doing when they determined the overall gearing in high gear and the engine rpm when doing highway speeds your engine will be more prone to detonation.-I was Triumph spec I quoted with the BP6ES
- If you are convinced that Triumph didn't know what they were doing when they suggest a spark plug your engine will be more prone to detonation.-See above
- If you are selecting the grade of plug for fuel or oil fouling, instead of temperature your engine will be more prone to detonation.
- If you haven't removed all of the sharp edges on the piston and combustion chamber your engine will be more prone to detonation.-This engine was rebuilt years ago, hasn't been opened since.-
If the valve margins are too thin, they will not cool properly your engine will be more prone to detonation.-Rebuilt with stock valves
- If you do anything to hinder the transfer of heat out of the cylinder and head fins your engine will be more prone to detonation.-Such as?
- In places where the ambient air temperature exceeds 100° F being careful of riding style and monitoring oil temperature is something I would consider.

The ability to control heat is the limiting factor in what you can expect from one of these engines."-The new pipes aren't bluing, so....

On top of all that, I haven't heard anything resembling pinking much less detonation.
 
All it takes is a few minutes of detonation to melt a piston say on a uphill grade, on a hot day with a bit of a load . Plenty of examples of that. You may do fine running a plug one heat range higher but you are adding an unneeded risk factor. If you have oil fouling you need to find out where the oil is coming from, either valves or rings. Running a hotter plug is just a band aid.
 
Not sure who is recommending a hotter spark plug as a band aid, only a plug of the recommended heat range. As LAB pointed out above, even Norton upped the heat range recommendations.

Without seeing the wet plug that the OP mentioned it is difficult to say whether it is all attributed to a fouled plug or an engine in bad order.

John leathers said:
Bike is hard to start as seam to be on one cylinder, feel exhaust pipe one hot one cold. Remove plug it seems a little wet with slight oily look to it.

It sounds like the bike is running ill (on one cylinder) so not sure how much you can read into the plug reading on the non firing cylinder other than the plug is not firing and the plug is wet. It's a single carb so that simplifies things a little. If it cannot be cleaned up with proper plugs and a good flogging on the road to clean it out then look elsewhere.
 
The main determining factor of a spark plugs heat range is how well the cylinder head is able to dissipate the heat from the plug. Water cooled engines generally run hot plugs and air cooled engines run cooler plugs.

A ngk grade 6 plug may be death to a Norton motor if the engine is tuned to a high performance state. A stock 750 with twin carbs jetted to maximum power will be damaged pretty quickly running a plug as hot as a "6".

An NGK grade 7 is pretty safe in a standard engine although Norton did at one time suggest going one step cooler for "extended high speed operation" An 80 mph interstate run or a pull up a long hill will be borderline safe with a "7"unless the jetting is on the rich side.

Anytime an engine is modified to create more power -it is likely to increase running temp of the cylinder head. If the cylinder head is running hotter then the plug heat should be changed to a colder plug.

If your standard engine is fouling an NGK grade 7 plug then the correct thing to do would be to correct the jetting -not go to a hotter plug. If you do go to a hotter plug then you run the risk of finding a place in the jetting were the mixture is not over-rich and engine damage may happen quickly. Jim
 
Apologies to original poster. This thread drifted off course to a discussion about another thread that concerned running a hotter plug to counter oil fouling.
I run NGK BPR8E's in my 750 with good performance, heat indicator in the middle of the strap bend, carbon on 1/2 to full turn thread flat, sharp electrode edges.
 
L.A.B. said:
Biscuit said:
My 850 is spec'd for Champion N 7's This is hotter than the N 3's spec'd for the op's 750.

The original Champion plug grade specified for the 750 was N6Y (equivalent to NGK BP8ES), however, during 1971, the recommendation changed to N7Y for all 750 models, including Combat.

Ok, I confess I was going on what Dances w Shrap said a few posts back about the Champ N3's being just one step cooler than what OEM (Norton?) recommended. Sorry.
?
 
Biscuit said:
L.A.B. said:
Biscuit said:
My 850 is spec'd for Champion N 7's This is hotter than the N 3's spec'd for the op's 750.

The original Champion plug grade specified for the 750 was N6Y (equivalent to NGK BP8ES), however, during 1971, the recommendation changed to N7Y for all 750 models, including Combat.

Ok, I confess I was going on what Dances w Shrap said a few posts back about the Champ N3's being just one step cooler than what OEM (Norton?) recommended. Sorry.
?

The obvious difference is the N3C non resistor - non projected tip plug.

According to this chart:

http://www.federalmogulmp.com/en-US...n Spark Plug Copper Plus Heat Range Chart.pdf

The N3C may be comparable to a champion N9YC (Projected tip) or a RN9YC (Projected tip resistor).

Yet this page below shows the N3C equivalent to a BP8ES

http://matchlessclueless.com/mechanical ... ark-plugs/

which is in line with my original statement which is:

A Champion N3C is one plug range cooler than that recommended by the OEM.

As my understanding is a BP7ES is an OEM equivalent recommendation.
 
Funny... According to this "other" Champion chart from 2013 an N3C is equivalent to an N6YC. This is what I've always seen in the charts.

http://www.fme-cat.com/digipubZ/Champio ... ark-Plugs/ on page 244

For Champion, C = Copper core center electrode, Y= projected nose. Original plug specified for my '72 is N7Y. The copper core C version came out years later as an improvement and the regular N7Y was discontinued. A projected nose plug is "in the wind" more inside the cylinder so cools faster than a regular plug. So the 6Y can be equivalent to a 3.

I seem to remember there was a great Gordon Jennings article on spark plugs in Cycle magazine. Will try to find it. Edit - 1977 Cycle article - here's a link - http://www.strappe.com/plugs.html

Russ
 
Most every reference I see indicates a Champion N3C is comparable to an NGK B8 and at least indicates a Champion N3C is comparable to an NGK B8 or B9. That is on the colder end of the spectrum.

With the link below, if you scroll down to the section titled Summary of alternative spark plugs you will see an example of what I am seeing. Note these are non projected plugs.

http://matchlessclueless.com/mechanical/ignition/spark-plugs/

Perhaps we cannot assume that an NGK non projected and projected of a given heat range number are equivalent. If equivalent, the OP is using really cold (N3C) plugs and being non projected may not be helping things. I would think a projected plug would naturally have a greater heat path from the outer electrode, thus potentially hotter but that is really speculation on my part.

Bottom line is that an N3C is the wrong plug for the application. An N3C will certainly get you running in a pinch but if the OP's problems have been chronic, then cylinder washing with raw gas on the missing cylinder may have come into play, thus oily plug on one side. I am not nor have I suggested running a hotter plug and comnoz explained the perils of doing that.

On the other hand, there may likely be another underlying problem such as tuning or other aspects of the ignition at play here. In my opinion, getting the correct plugs of the correct heat range is one of a few easy steps towards resolution.
 
Dances with Shrapnel said:
Biscuit said:
L.A.B. said:
The original Champion plug grade specified for the 750 was N6Y (equivalent to NGK BP8ES), however, during 1971, the recommendation changed to N7Y for all 750 models, including Combat.

Ok, I confess I was going on what Dances w Shrap said a few posts back about the Champ N3's being just one step cooler than what OEM (Norton?) recommended. Sorry.
?






The N3C may be comparable to a champion N9YC (Projected tip) or a RN9YC (Projected tip resistor).

Yet this page below shows the N3C equivalent to a BP8ES

http://matchlessclueless.com/mechanical ... ark-plugs/

which is in line with my original statement which is:

A Champion N3C is one plug range cooler than that recommended by the OEM.


quote]

Ok, I apologize here too. I'll admit I did not get deeply into plug charts. Really my only thoughts on plugs & engines was not to get specific, but only to say if an OEM specifies a certain plug for a particular engine, changing plug heat ranges as a tool to tune out plugs fouling for any reason is not getting to the root of the underlying problem.

And I just read your last post, Dances. Your last sentence is exactly what I too am getting at.
 
Spark plug cross reference charts are only rough estimates. For tuning a standard engine you should start with the manufacturers recommended plug or a proven replacement.

Projected or non projected plugs will often change the operating temperature of a plug -but not always as you would think. With a projected tip plug it may run hotter in some engines but run cooler in other engines. I depends on how the mixture moves in the chamber.
A Norton motor has a lot of swirl in the chamber and the incoming charge is directed right over the spark plug and tends to cool a projected tip plug.
I have to say I have not seen a big difference in spark plug temp between a projected and a standard tip in a Norton. The non -projected tip often needs a degree or two more timing advance.
 
And this extra degree or two gets back to my flame kernel remark earlier in this thread. Anytime you must advance the timing you are loosing power and efficiency opportunity. From what Jim is telling us I am concluding that the retracted (non projected) tip (in this particular application) is generally slower at lighting off the air/fuel mixture. There may be an exception to this but I am not aware of any.

As a side note, the Nourish Race Engine recommendation is a Champion G55R which drives me nuts.

Spark plugs (2016)


When I look at this plug I say (with tongue in cheek) why even bother. I always wanted to ask Dave Nourish about this; maybe it is a lack of space and/or likely tumbling turbulence of a four valve combustion chamber. I know heat can be an issue in the Nourish Race Engines though I have not had any problems so far and I do run the G55R.
 
Yes, the retracted tip plug is likely to make a smidge less power because it is slower in starting the burn.

The reason it is used is because it is pre-ignition proof. There is nothing to overheat and glow.

Of course if using a retracted tip plug means you can jet closer to the ideal mixture without encountering pre-ignition, then you will end up with a power gain.

I have found on my bike I can make a little more power using a surface gap plug and jetting a little leaner.
 
comnoz said:
Yes, the retracted tip plug is likely to make a smidge less power because it is slower in starting the burn.

The reason it is used is because it is pre-ignition proof. There is nothing to overheat and glow.

Of course if using a retracted tip plug means you can jet closer to the ideal mixture without encountering pre-ignition, then you will end up with a power gain.

I have found on my bike I can make a little more power using a surface gap plug and jetting a little leaner.


Do they still make those? I remember using them in my '69 Kaw 3-cyl. 2-stroke, and they were pretty foul-proof. According to their manual, surface-gap plugs were a requirement for their CD ignition, but other, regular plugs would work as well.
 
Danno said:
comnoz said:
Yes, the retracted tip plug is likely to make a smidge less power because it is slower in starting the burn.

The reason it is used is because it is pre-ignition proof. There is nothing to overheat and glow.

Of course if using a retracted tip plug means you can jet closer to the ideal mixture without encountering pre-ignition, then you will end up with a power gain.

I have found on my bike I can make a little more power using a surface gap plug and jetting a little leaner.


Do they still make those? I remember using them in my '69 Kaw 3-cyl. 2-stroke, and they were pretty foul-proof. According to their manual, surface-gap plugs were a requirement for their CD ignition, but other, regular plugs would work as well.

Yeah, there still used -mostly in boat motors. Surface gap plugs require a very hot ignition system to work very well. Jim [my 69 -H1 was my introduction to surface gap plugs also]
 
I run B9ES's in the 10:1 race motor and B7ES's in the 8.5:1 road bike with very good results all round.
(non P and R plugs)
Ignition in the road bike is 2 x 6V coil Pazon Surefire with 5K resistance caps
Ignition in the race bike is RCR crank triggered, 2 x 6V coils also with 5 K resistance caps
Regards Mike
 
comnoz said:
Spark plug cross reference charts are only rough estimates. For tuning a standard engine you should start with the manufacturers recommended plug or a proven replacement.


.

This is something ,I'd say few people really know. This included myself, before this discussion. I had known that cross references could be "off" a bit but not to any real important degree, certainly not to the extent of several heat ranges. Comnoz's statement above, In my opinion is the safest and surest way to make sure the right plug is being used. I am not a blindly loyal Champion, NGK, Autolite, Bosch, or any other brand of plug guy. I think they are all fine but to be sure one is using the absolutely perfectly spec'd plug, it's probably best to stick with the brand and numbers the OEM calls for. In my MK3, since new I have always used Champion NY7C with never an issue. Apparently an NGK B7ES is a "proven replacement" so I'd be comfortably with a set of those too, but unless I was willing to put some serious research into it, I would not use another brand based on a plug cross reference chart.
 
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