Bonneville America Forums Forums Technical Forums General Tech Spark Plug Colour

OK, checking the plugs is a very good indicator white = lean , Brown or tan to greyish brown = good ,black or sooty = rich.

In cars I have always found the colour on the insulator very even and the body and electrodes usually grey. I pulled the plugs the other day and found an interesting pattern in that approx half the insulator was a greyish brown, the other half was closer to white, and the side electrode and bottom of the thread body was black/sooty. I must be running lean on one side, OK on the other and rich. around the middle

I have recently change pilots to a bit richer (500kms ago). Total of around 1,500kms on the bike. I know the bike was running lean at that time. I'll check again in 500kms and try a new set of plugs at that time and see what happens...

Are you torqueing the plugs down sufficiently?

I have found that, trying not to over-tighten mine, when I go to remove them again several thousands of miles later, they always come out a lot easier than I anticipate. Not loose, but very little effort to loosen them. Never torqued mine, but I did snug them a little tighter last time. I don't want to strip a thread, or crack a head, but I know a loose plug would be a bad thing, too.

I have really grown to like the sound of my TORs, but when I rejetted to 125 mains, I should have used the 130 mains I had handy. My bike runs great, but the spark plugs are still very white after several thousand miles.

I could just put the stock pipes back on, and that, I'm sure, would solve the problem as well.

Decisions, decisions.....

It might be that the carburettors are out of balance. Then, even if all else is the same on both sides, one will run harder at speed, but it won't quite reach the idle position. The other side will be the opposite, running fully on the idle jet when the throttle is closed, but loafing along at speed.

I have seen a little difference from side to side before, If you are white on one side (remember this is without my actually being able to see the plug) I would say probably a little lean but not bad if are getting some color. Still would adjust it some though.

Wasn't there a thread some time ago that talked about shimming the plug with washers to get the spark front to face the intake valve? This method has a name, but I can't remember the word for it just now.

It's called indexing.

I've noticed that the upper part of the ceramic is where the true colour lies. Might have to do with the strange batch of chemicals they are passing off as petrol these days.