Spark plug???

gtsun · May 27, 2013

I've been using NGK B7ES for just cuz that's what was in it when I got it. But allmost put a B ( P ) 7ES in from my Norton & wondered what's the differance & why. My book calls for Champion NY6 so for you more learned 441 BSA single owners, what's the best plug to use???

Rohan · May 28, 2013

The P means projected (electrode) in NGK speak, and sticks out into the combustion chamber a bit further.
Can supposedly make it burn a shade hotter, which can make it useful if an engine is burning a little oil or a little rich = keeps the plug clean.
Fine if thats what your engine is used to / tuned for.

No idea about in a BSA though.

kommando · May 28, 2013

I use a projected plug in my B44, works fine and seems to help cold starts.

johnm · May 28, 2013

Rohan said:
The P means projected (electrode) in NGK speak, and sticks out into the combustion chamber a bit further.

Projected tip plugs are excellent. However you do need to check clearance to the piston.

Gordon Jennings was very keen on them. They put the spark out more central in the chamber, they can get a cooling blast from the incoming charge.

I have used NGK BP9ES plugs in my race bike for years. No issues with petrol and methanol. 500 cc, 51 BHP rear wheel.

grantlaney · Jun 12, 2013

I am always go with projected plug. It is very good for use.

xbacksideslider · Jun 12, 2013

I favor projected nose plugs too, probably got the idea from reading Gordon Jennings back when. They do advance the effective, or dynamic, spark timing of the engine though because they start the fire farther out in the wind stream of the combustion chamber and farther from the coolness of the head and the cooler boundary layers near the chamber surface.

I also like the platinum or iridium center electrode plugs because the smaller and pointier, the electrode, the larger the gap that can be run. Theory is that a greater gap ignites more gas charge, more consistency. Same effect, slight advance in the effective, or dynamic, spark timing. Sharp electrodes can also overcome the quenching of the spark that high compression, or a weak ignition system, can cause.

Take note that there are now precious metal "long mileage emission plugs" that do not have a fine wire center electrode but instead they have a spot welded nub of precious metal on one or even both electrodes; I avoid those because they are not sharp points.

gtsun · Jun 14, 2013

Thanks John, You answered another question to something I was trying to learn about, the differance gap size makes. Thanks again. Glenn.

Hobot · Jun 14, 2013

Widening the gap tends to delay/retard the timing d/t taking a bit more time to build voltage to jump. Proper timing give thermal stain a bit before the hook bend begins. Generally want as big a gap as the ign. system can reliably fire.

Ok what would be the best direction to index the gap facing in Norton heads or BI hemi's in general?

Ziggy · Jun 14, 2013

hobot said:
Widening the gap tends to delay/retard the timing d/t taking a bit more time to build voltage to jump. Proper timing give thermal stain a bit before the hook bend begins. Generally want as big a gap as the ign. system can reliably fire.

Ok what would be the best direction to index the gap facing in Norton heads or BI hemi's in general?

Widening the gap (and compression) requires a high break over voltage to jump the plug gap, the higher the RPM the less time the coil has to reach break over voltage. When the switch (points or transistor) closes the coil is turned on and when it is turned off (Dwell or Coil saturation time) the spark is hopefully induced across the spark plug gap. If the coil is not fully charged you can get a weak short duration spark or no spark but there is no effect on the timing. Weak spark can mimic retard as you have a lesser burn of the available fuel but the ignition timing has not changed, you only have the result of a poor ignition.

Indexing a plug depends upon the cambering and head design as the sparking of the plug occurs 180° (degrees) out from the intake cycle. Lowing the plug gap to maintain a consistent spark and filing you spark plug ground strap to a point > roughly centered over the center electrode will see better gain.

Nater_Potater · Jun 14, 2013

hobot said:
Ok what would be the best direction to index the gap facing in Norton heads or BI hemi's in general?

Back in the drag racing days (cars), we would start with the ground electrode's anchor point opposite the intake valve. I guess the thinking was that the incoming charge would have an easier time of cooling the ground electrode if its pointy end was facing the intake valve. We screwed around with it for a bit, but never could see any conclusive results, i.e., it must have been a marginal variable, if it changed anything at all. The big boys who played around with lots of nitrous and/or blower pressure were more concerned than we were, so I don't imagine it would make much difference on our Snortons unless you were running a blower.

chilly · Jun 15, 2013

We couldn't get my mates Mk 3 to run right , especially on tickover , stripped carbs and cleaned etc to no effect , as a last resort i said about trying some ordinary Champion N3 plugs instead of the fancy Irridium plugs he had fitted , Bingo , bike ran a treat

The bike is running a Boyer Ignition , maybe it just doesn't like the fancy plugs ? .

Triton Thrasher · Jun 15, 2013

chilly said:
We couldn't get my mates Mk 3 to run right , especially on tickover , stripped carbs and cleaned etc to no effect , as a last resort i said about trying some ordinary Champion N3 plugs instead of the fancy Irridium plugs he had fitted , Bingo , bike ran a treat
The bike is running a Boyer Ignition , maybe it just doesn't like the fancy plugs ? .

Any mechanic would tell you. Plugs first, then points.

As you had no points, it's plugs first, then internet.

Matt Spencer · Jun 15, 2013

Wonder what plugs the P.R. runs .

The extended nose things are to prevent fouling / self cleaning .

Can get a bit hot under race conditions . So may not be the thing for fast movers ?

chilly · Jun 16, 2013

Triton Thrasher said:
chilly said:

We couldn't get my mates Mk 3 to run right , especially on tickover , stripped carbs and cleaned etc to no effect , as a last resort i said about trying some ordinary Champion N3 plugs instead of the fancy Irridium plugs he had fitted , Bingo , bike ran a treat
The bike is running a Boyer Ignition , maybe it just doesn't like the fancy plugs ? .

Click to expand...

Any mechanic would tell you. Plugs first, then points.

As you had no points, it's plugs first, then internet.

Just how many times have i said that :roll:

xbacksideslider · Jul 1, 2013

chilly said:
We couldn't get my mates Mk 3 to run right , especially on tickover , stripped carbs and cleaned etc to no effect , as a last resort i said about trying some ordinary Champion N3 plugs instead of the fancy Irridium plugs he had fitted , Bingo , bike ran a treat
The bike is running a Boyer Ignition , maybe it just doesn't like the fancy plugs ? .

Did he have resistor caps? If so, that's a problem.

Both NGK and Denzo iridium plugs have built in 5 ohm resistors. If you put them under the 5 ohm resistor caps that many bikes come with, then you have 10 ohms of resistance.

Rohan · Jul 1, 2013

Matt Spencer said:
Wonder what plugs the P.R. runs .

The extended nose things are to prevent fouling / self cleaning .

Can get a bit hot under race conditions . So may not be the thing for fast movers ?

In case you hadn't noticed, Champions made more than one grade of sparkplugs. !
You use a colder plug than the N7Y.
Champions get colder as the number gets lower - so a N6Y or N5Y or N4Y, etc.
With probably a few extra letters in them, these days.

And then there is the ubiquitous N57R, a racing plug, mucho costo (compared to roadbike plugs anyway).
No projected nose on this one, keeping it cool enough to keep going is the name of the game.