My plugs are suspiciously clean.. How lean is too lean?

Vincent · Post by **Vincent** » Wed Feb 11, 2015 10:31 am

Quick question - how lean is too lean?
My old plugs were a bit tired (too much rich running while experimenting with jets and idle mixtures has worn them out!) so I treated the NC30 to a new set today. The old ones were a nice light brown colour around the insulators but tended to get a little bit sooty over time.

After a 100km ride with the new plugs in with lots of high RPM and WOT, I pulled them to see if I was running rich. Based on how the old ones looked I was expecting a bit of soot, and maybe having to go down a jet size.
There was only a tiny bit of soot on the base ring, and the porcelain insulators were still crisp white!

It's running a straight-through short carbon fiber muffler on cut stock headers. Jetting is 118f/120r with one extra shim under the needles.
During the ride it revved fine straight up to redline, and didn't feel flat anywhere.

I'm not really worried, as there are no lean flat spots, and she's running beautifully.
Just wondering if you guys are getting nice tan coloured plugs with similar carb/exhaust set ups, or if they're staying reasonably white.

Post by **Neosophist** » Wed Feb 11, 2015 5:21 pm

plugs are a good indication of running but do you have access to a dyno?

youll get a much more comprehensive picture of the fuelling system and a better base to work from

Vincent · Post by **Vincent** » Thu Feb 12, 2015 2:57 am

There are a few dynos around, but I'm a poor student so paying $200 for a dyno run isn't really an option for me unfortunately.
The plugs have discoloured slightly from what they were when brand new (a slightly softer white), so it's probably just running on the slightly lean side of OK.
I'm just rather pedantic and like to get things perfect. It bugs me if things aren't working as they should.

Vincent · Post by **Vincent** » Thu Feb 12, 2015 5:27 am

Went for another long ride, pulled the rear plugs and took a photo (they were identical).

Post by **Drunkn Munky** » Thu Feb 12, 2015 7:51 am

In my opinion its pointless doing a plug chop unless your going to cut the engine under load at the desired RPM

Post by **Morespeedvicar** » Fri Feb 13, 2015 1:54 am

looks near enough to me, especially on unleaded, these days it seems to burn a bit different than good old leaded fuel. Sometimes you can tell its a bit lean if you get it wide open an let the throttle off a tiny bit, if it picks up its lean.
But if its running well I'd leave it be.

My plugs are suspiciously clean.. How lean is too lean?

My plugs are suspiciously clean.. How lean is too lean?

Re: My plugs are suspiciously clean.. How lean is too lean?

Re: My plugs are suspiciously clean.. How lean is too lean?

Re: My plugs are suspiciously clean.. How lean is too lean?

Re: My plugs are suspiciously clean.. How lean is too lean?

Re: My plugs are suspiciously clean.. How lean is too lean?