E: Engine Spark plugs 1000 and 500

[mirkothun]

Hi there,
I‘m just looking for the right plugs for my Egli Black Shadow running on 32 Concentrics Mk 2. The rear cylinder stops running occasionally. Plugs used are NGK BR7ES.
On my Comet Metisse I got missfires on the last run, she didn‘t take any throttle anymore and then went of. Is it something with the carb or some ignition problem? Maybe the spark plug. It came with boyer bransden ignition, twin plug head and NGK BR9ES... What would you recommend?

 

[Bill Thomas]

I have found that Champion N9y work well for me, Or N5 for an old type mag'.
Some of us have had trouble with NGK since this new type Petrol came out.
Try not to run too rich, I have had to run weaker slides in my carb's because that's where we ride most of the time, Up to 70 or 80 mph, 1/4 ish throttle, I run 36 mm Dellortos or 30mm amal mk2 carbs.
Cheers Bill.

 

[Normski]

With a twin burning a lot of oil due to poorly bedded in rings (my fault) I was using Champion N6 or NGK B4ES to keep them clean. That's not healthy and is covering for a problem not addressing it, however I think you could try B6ES quite safely. Most people try to avoid the resistor plugs in older bikes i.e. Not BR prefix.

 

[chankly bore]

Original Japanese NGK BP7ES are fine on the Comet on Steroids with twin-plug Pazon ignition. "9" grade is a bit too cold for the plug to keep itself clean, I would have thought. My original Comet runs an original KLG (Guinness is good for you) FE70. Still working fine with a well-sorted magneto. Original Japanese NGK B6ES work fine as well.

 

[Robert Watson]

I think the ignition system has as much to say about spark plugs as does the cam/compression/bore/stroke.

On the new BT-H CDI ignitions I have tried to run NGK 7's and find them a bi^*_ to start when cold, both on a MK1 cam 7.3:1 twin and on a 636 Comet with fairly high comp. Both became easy starters with a 6.

 

[greg brillus]

I have to agree on those points, it seems a fine line between a plug that will burn off sooty deposits and one that gets hot enough to promote detonation. I choose between 5's and 6's anything higher is too cold and will soot up given most of these engines run quite rich. Some engines like protruded tip plugs too like a BP5 ES or similar, the fine wire ones work ok but the extra expense is really wasted. I'm with you Robert, with regards to the BTH whose spark at low speed seems quite week, and I am leaning towards reinstalling the original Lucas mag on my Rapide for easier starting. As great as all these new ignitions are (or seem to be) it is still very hard to beat the output from a descent original magneto.

 

[Mike 40M]

Some people say that NGK plugs should never be bought on ebay, since there is a lot of fakes.
There is also the opinion that NGK plugs made in France have a finer grade of ceramics, that only works well in modern lean engines. For our old oilconsuming and richer air/fuel mixture engines, they recommend plugs made in Japan.

 

[greg brillus]

Bill has mentioned on here about his thoughts on Champion verses NGK's in that the Champion plugs seem to fair better against sooty/oil deposits because the center electrode has a coating that is different to the NGK's. I have no reason to disagree, and this seems to be the case. It is also possible that the NGK's might not handle the temperatures of air cooled engines as well..........Who knows. There are definitely some aftermarket fake NGK's out there that are rubbish, so maybe this is more the case than across the board with these excellent plugs. There can be a fine line between an engine that runs well with no plug problems and one that is either too rich or using oil enough to cause reliability of these engines. Before I rebuilt my bike a couple of years ago, I had a plug problem that ended up being the needle jets in the stock 276 carb's were worn enough to allow too rich a mixture, thus fowling the rear plug...... After replacing the needles and 106 needle jets.......... problem all solved. Cheers............Greg.

 

[Bill Thomas]

My Bikes are all Ex racers and worn out like me, I tend to run them as rich as I can because I want them to go,
Soon after start up and not Nip up.
I have been to many Vin' meetings and seen people go home with the carbs misfiring because of weak settings. Years ago with new type water cooled Bikes, They would start the Bikes and leave them running
While getting there stuff on, Not sure about them now.
We have to remember that some places are much hotter than we are here.
I have found the N9y even better for me than N5, But they have a gap inside so not good for old type Mag's..
Cheers Bill.

 

[Cyborg]

http://www.ngk-sparkplugs.jp/english/techinfo/fake/index.html