Correct spark plugs for my 500 ?

[McCabe-Thiele (Ted)]

Parts manual shows NGK D-7ES or Denso X-22ES

The Denso seems to now have a U at the end now shows as Denso X-22ES-U

The NGK looks as though it is obsolete - I have resistor caps so don't want NGK DR-7ES.

Green Spark Plug Co shows the Denso X-22ES-U at good price.

Can't find my old spark plugs - I've been using some used NGK D8EA plugs to keep debris out.

[Nurse Julie]

Denso X22ES-U is the correct type.

[Johnwebley]

If you ride it, quite quickly, for a 70s bike

Mine runs great on the 24s



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[deltarider]

In The Netherlands dealers advised the D8ES-L (or the ND equivalent). The "7" was considered the plug for break-in period only. This was advised because we used to ride at maintained high speeds. US riders usually have the 7. They prefer to ride at lower rpm's.

[Bryanj]

IF you can find any D7EV are the muts nuts but expect to pay £8 ish EACH

[mickwinf]

d7es replaced by d7ea.

[AshimotoK0]

Denso X22ES-U is the correct type.

Going to go with these Julie as heard there are a lot of fake NGK's around. Do you have a reference for ND for CB750K0 and 400/4 please?

[Sesman]

I don’t believe Greenspark supply fake NGK. Just saying…..

[davidcumbria]

I’ve gone for the denso ones from green spark who didn’t have the ngk in stock at the time. Run iridium in most of my bikes which definitely help starting but can’t see one for the 550.

[deltarider]

[...] Run iridium in most of my bikes which definitely help starting but can’t see one for the 550.

Any new sparkplugs will help starting. Some in the German forum have tested iridium plugs but were not impressed. These plugs will do well in modern bikes however which run much leaner than our filthy beasts.

[K2-K6]

Denso X22ES-U is the correct type.

Going to go with these Julie as heard there are a lot of fake NGK's around. Do you have a reference for ND for CB750K0 and 400/4 please?

Original std for 750 K0 listed as D8 ES in Honda workshop manual, no equivalent for ND. Later manual lists D8 EA with ND "X24ES-U" as direct alternative. 

[Nurse Julie]

Denso X22ES-U is the correct type.

Going to go with these Julie as heard there are a lot of fake NGK's around. Do you have a reference for ND for CB750K0 and 400/4 please?

X24ES-U Ash.

[K2-K6]

[...] Run iridium in most of my bikes which definitely help starting but can’t see one for the 550.

Any new sparkplugs will help starting. Some in the German forum have tested iridium plugs but were not impressed. These plugs will do well in modern bikes however which run much leaner than our filthy beasts.

It's primarily about service life and gap change during that lifing to meet intervals in schedule as opposed to significant changes in performance of the plug.
Before these materials they were heading toward twin and triple earth type plugs for durability (typically toward 36,000 miles in car engines) ultimately superseeded by this type of plug with more resistant materials.

[Bryanj]

Many years ago our NGK rep was  gent called Stan Dibden who used to be a sidecar racer, just by looking at the plugs from a GT 250 he advised stripping as a piston was holing and he was right.
He also gave me a set of D7EV for my 500 and i found it started cleaner, ran better and gave better mpg.
That plug has been long discontinued and if you can find them its £8-10 EACH, i am lucky to have bought a few sets years ago

[Skoti]

Aye,

Stan Dibben former sidecar world champion, NGK spark plug rep and recent vice president of the Norton owners club.


Here's a clip from the New York Times  https://youtu.be/V_8vr_4qa2g (7mins)