Spark Plugs Dommmie 88

I find Champion N5c work well.

What ever you buy (I use NGK) make sure it is from a reputable dealer, there are lots of fakes out there that either dont work or dont last.

Dan 

Champion plugs in all my bikes, never a bad one.

I ran the same N5c in my slimline Mod 50. It finally gave up after 23 years of use.

I dont know if the  later Champions still have properly glazed insulators ( not deemed necessary  for anything modern and lean burn), I  always buy ancient stock which has usually been able to burn off carbon once hot and given some welly . Could be the reason Neils lasted so long.!.  At some point in time some  plug makers  re-graded their range recommendations , perhaps this coincided with  a change to the glaze?. Hotter plugs needed to burn off the carbon that the new (cheaper) unglazed insulators could not cope with ?.Stan would have had something to say about this.

When I  found out about the E scam, Robert, (2007) I just run on E0. I'm certain that gives the plug an easier time with heat etc.

seems risky.  I bought a pair of NGK BP6ES plugs, exactly the same spec as my old ones, from a local car parts shop.  They gave the bike a persistent stutter, only cured by fitting some old plugs. 

I’m totally new to classic Nortons so feel free to ignore this, but I’ve had similar issues with the 1972 air-cooled VW camper we’ve owned for over 20 years. As part of a service, I’d replace the NGK plugs (that seem to suit the engine) only to have it misfire under load, oil the plugs and generally not run as well as before. Once swopped back, everything was happy again.  Talking to other owners, I’ve found that the general feeling is that there’s a lot of counterfeit plugs out there, NGK especially, and many prefer to stick with a known good set of plugs rather than routinely change them as a service item. 

I have had similar problems with my BMW sidecar outfit, fake NGK B8HS lasted 20 miles but KLG F100s from Greens are great and just need a clean every now and then, and are cheaper...

But of course those are short-reach and FE100s are a bit harder to find.