SOHC.co.uk Forums > CB500/550

Plugs fouling at idle

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K2-K6:

--- Quote from: Bryanj on April 24, 2024, 10:28:55 AM ---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

--- End quote ---

Thats noted on some published charts too .... the -L designation.

https://www.ngk.com/ngk-spark-plug-numbering-systems this lists that design element, although note that they have a statement of NOT being NGK USA official scource.

The listed data looks comprehensive though.

deltarider:
Aha, that is valuable information. I had not seen this half-grade mentioned before. In Holland the general advice was to have the D8ES-L. Let me put it like this: if the D8ES-L fouled, than a "7" also did.
Now that we're older  ;) and also have a lower national speed limit than back then, both the 7 and the D8ES-L can be used no prob.
I am curious if the D8EA is identical with the D8ES-L and if the D7EA also has a tip that protrudes just a fraction more than the D7ES. I have tried to see the difference myself, but I'm afraid the difference is minor and... older eyes don't help either. ;)

Johnwebley:
Back in the 80s

I also used Champion A8Y


Definitely a  projecting nose plug,

The bike ran well, but they became difficult to get

Sent from my SM-A546E using Tapatalk

K2-K6:
Not owning a 500, I've not that specific experience to offer.

A big BUT though, genuinely I've never had problems with plug "fouling" on four stroke engines, that's across all bikes and cars I've looked after since early 1970s.

Another observation, the Boyer ignition is very, very competent in it's delivery. I've no problem working with the std system, believing it to be mechanically almost peerless in it's design, application and component specification .... the Boyer i can see by comparison does offer tangible benefits if that's chosen by the owner though.
Among those benefit appears the ability to fire more adverse mixture range more of the time with exceptional repeatability.  This seems to support a more optimum idle mixture that may give benefit in any residual unburnt component/fuel that may be affecting the fouling determination this topic is about.

Very loosely, NGK plug heat range on these engines could be approximated to continuous load under wider throttle for extended periods of time.
 A 7 giving ROUGHLY decent coverage for 7000 rpm running.
Likewise, an 8 for predominately covering an 8000 rpm consistent load type riding. Etc, etc
Basically its a balance of number of actuation per minute against heat clearance from the engine, ambient air temp also playing a part in air cooled motors too.

florence:
I agree completely which is why I was asking if the fouling might have another cause, nothing to do with plugs.

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