SOHC.co.uk Forums > CB500/550

Plugs fouling at idle

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Bryanj:
Delta, i disagree,
On the asvise of an ngk rep who was a well respected sidcar racer i used D7EV in my 500 that went all over the UK and to the Isle of Man regularly plus commuting 7 miles to work.
Never fouled, never failed yes nearly twice the price but well worth it  the =L was always sold as a "half grade"

deltarider:

--- Quote from: Bryanj on April 23, 2024, 06:50:28 PM ---Delta, i disagree,
On the asvise of an ngk rep who was a well respected sidcar racer i used D7EV in my 500 that went all over the UK and to the Isle of Man regularly plus commuting 7 miles to work.
Never fouled, never failed yes nearly twice the price but well worth it  the =L was always sold as a "half grade"

--- End quote ---
NGK came with the D8ES-L for a reason. Other plugs that had a less protruding electrode, fouled. That problem needed to be adressed. In my documents, the D8ES-L was characterised by NGK as "Special Design". Although it's been interpreted by forum members as "half grade" I've not seen this confirmed by NGK as such, nor by Honda. As the D8ES-L indeed fouled less, it could be used by CB500/550 owners that had read in their Owner's Manual and I quote: [...]" if the motorcycle is going to be operated for extended periods at extremely high speeds and near maximum power in hot climates, the spark plugs should be changed to a colder heat range number." That the American EPA was somehow involved in the birth of the D8ES-L, is a story that so far comes from one member only in the international forum. I have seen no confirmation of that story yet. I mean: how about all the other markets that didn't have an EPA?
Back in the day, every owner of a CB500/550 on the European continent ran the D8ES-L plug. My personal experience was that this plug fouled no more than the D7ES did.
One of the best manuals I have, is the French one that was established in close participation with Honda France. On page 83 we read:
Bougies
La CB 500 est équipée de NGK D-7 ES alors que le modèle actuel (CB 500 K1) possède des bougies NGK D-8 ES-L qui ont la particularité d'être autonettoyantes. Il est conseillé de monter également ces bougies sur la CB 500.
In translation:
The CB 500 is equipped with NGK D-7 ES while the current model (CB 500 K1) has NGK D-8 ES-L spark plugs which have the particularity of being self-cleaning. It is recommended to also fit these spark plugs on the CB 500.

And that's what most of us did.

I'm sorry I cannot comment on experiences/reviews which may be biased by free handouts. Untill I have more information, I consider them anecdotal.

 

florence:
On my 500, I have D7EA and it ticks over perfectly, they do not foul.  Good response in all rev ranges, hot and cold.

Perhaps you should look at ignition timing and carbs rather than plugs.

Bryanj:
The fact that the L was a half grade came from the same reptat suggested d7ev to me, and that man knew how to read plugs

McCabe-Thiele (Ted):
This is starting to read like "Plug-gate".

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