I need to buy a couple of new plugs for my M21 engine. Does anyone have any recommendations on what's currently available?

For years I've used Champion L86C in my SV's (I don't like NGK) But lately I've been getting better results with Bosch W8AC. Both are available quite cheaply from Tim Green on line https://www.gsparkplug.com/ignition

I would suggest get some of each and try both. Ron

email (option): ronpier@talk21.com

I always fit a champion l10.
It is obsolete for many years now but i recently purchased 60 nos ones from them.

Yes and to that end Roy, I have found some original expensive KLG plugs to play with. But I just wanted to suggest some easy cheap modern plugs. Ron:relaxed:

email (option): ronpier@talk21.com

Thanks for these replies. Back in the day when this engine was a 500, I think N8 Champions suited? But haven't Champion reclassified everything?

N8 was for the alloy head wasn't it?...If that's the case the advice you've got so far isn't applicable as the alloy and iron heads use different plugs...Ian

email (option): ian@wright52.plus.com

Yes, Ian, the N8 is/was for the alloy head, which my engine has. But I said M21 in my post, aren't all M21s fitted with alloy heads?
Actually, the engine is a WM20 turned into a 600 the usual way.

The alloy head was introduced in 1951 and prior to that iron heads were used for both models...An N5C would be the current Champion plug for alloy head models...Ian

email (option): ian@wright52.plus.com

Thanks, Ian. I didn't know that.