what does this spark plug tell you?

[sam2019]

Is it too rich because it is black at the base
or is it too lean because the electrode is brown-ish?

 

[sam2019]

The piston going with this spark plug looks like this - both are at minimum 6000km in action

 

[Kiwiscoot]

I am no expert but I would read it as a bit rich because electrode is brownish. Whole spark plug brownish is normally spot on and sometimes the electrode can be more towards whitish then. The piston top looks like it was rich too but a bit hard to tell. If it was a carby bike I would've gone one size smaller on the main jet and check it again during a good run at a constant speed.

 

[Dool]

Both look okay to me

 

[sam2019]

well, OK, thanx mates, it will be a 500cc soon so if this is on the rich side as 477 it may just be all right for 500.

 

[Dool]

only 500?

 

[sam2019]

I do not want a Japanese kind of engine - anything above 500 and it becomes oversquared - also there will likely be limits with what the crank is happy in terms of angular momentum working on it and its bearings

 

[Dool]

Brisk on the right was out for a Compression test prior to a Dyno run tomorrow.
Pretty sure they are gapped correct from the box, Brisk was a bit tight can't remember putting it in let alone whether it was checked at the time

 

[thony]

Anything to read on this sensor

 

[Dool]

Corrugated Iron background and clean fingernails

 

[sam2019]

Often overlooked and forgotten: O2 sensor cleaning

.

forum.himalayan-tools.com

 

[thony]

Yeah, thoroughly cleaned already.