Spark Plug Health: lean / rich indication

[Gaz]

Hi All
I understand that the state of the spark plugs provides an indication of whether the petrol/air mixture is about right, too rich, or too lean. Black sooty plugs suggesting too rich, white burnt plugs suggesting too lean, grey with a little bit of black (not too sooty and not too white) suggests the mixture is about right (am I roughly correct??).

My question is this: is looking at just one plug a reliable indication of this or should all 4 plugs be inspected? Obviously looking at just one plug would be easiest as the 3 remaining plugs are more difficult to access. Any thoughts?

Regards
Gaz

[Zenarchy]

I had this link bookmarked that you might find helpful:

http://www.nightrider.com/biketech/spkplghnbook.htm

I've got a more detailed chart saved somewhere, but can't seem to find it at the moment (was more or less the same thing but had more pictures).

I'm not 100% certain (so better to wait until someone more experienced comes along before you check them), but I think you may need to check all of them to be sure as some of the conditions (oil burning etc) might not effect both cylinders at the same time, so only checking one plug might mean you miss something that would be apparent on one of the other plugs. As I say, not completely sure about that though, just a guess as it seems logical to me (but could be wrong).

[YEN_POWELL]

Check the two easiest plugs, the ones not buried down a deep mineshaft.

[BobA]

You should check 2 plugs as Yen says, but make sure one is from EACH cylinder.

Front and rear cylinders have their own carb, so in theory one could be running rich, the other lean, so check both. Also, both front and rear cylinders run at different temperatures, due to the front one getting more cooling air over it, and due to this, the carbs are jetted slightly differently.


Bob

[BobA]

I've had a re-think.

It actually worth checking all 4 plugs. Why? Well if one is damaged/broken/failed it may be the one you didn't take out!! A bike won't run great if it's got 2 plugs working in one cylinder and one in the other. It will feel lumpy, like the carbs are out of balance.

Worth remembering as well is that nothing on this earth, other than a Honda plug tool will get your spark plugs out properly. If you haven't got one, buy one for a £10 from WEMOTO.



Bob

[meljordan]

Hello buddy yes check all four and just as importantly service them.I mean take a mild wire brush to them and check the gap. they are one (well four actually ) of the most important parts of yer twin.
And if you want 200 to the tank they can help make the differance.
Makes sense when you think about it!

[Gaz]

Thanks all that have offered advice. Have checked all 4 (and cleaned them up) and they are fine.
Gaz