Two colored spark plug

Am I right in presuming I've started to run the saw on the rich side? (The darker side of the plug is facing down into the cyl...)

Q

Are you using leaded fuel.

Hey Ben, I use 92 unleaded and sometimes I get this on plugs. are you saying that it might be lead deposits?

I use an alcylate-based fuel, the "greenest" fuel there is. It's a synthetic 96 octhane unleaded fuel/oil-mix.

Q

that plug looks good to me.. looks like u may have just cranked it with choke all the way out,which may have caused the little bact tip.. jmo of course... its a new plug .. mite even be a little lean.

Looks hot to me and as if there has been some aluminum transfer. How does the piston and cylinder look?

Its hard to say without better pictures and knowing what oil/fuel your runing, but if I had to swag I would say your on the rich side. FWIW A plug can not be read by inspecting the tip. The part you read is down where the ceramic insulator meets the metal shell. There will be a mixture ring on the insulator. the leaner you are the fainter and lower on the insulator the ring becomes.
What you see on the tip is unburnt oil and fuel caused deposits. A perfectly jetted engine like a shifter kart will have a white plug and a creamed coffe colored piton with thumbnail sizes washes in front of the transfer ports. Also keep in mind that with a engine like a saw that sees constant throttle movement and very little sustained rpm its very hard to tune by reading plugs.

Warren Johnson shuts his car off with his foot to the floor and pushes the car off the track if he lacks the momentum to coast, why? Because he wants to be able to read the plugs, and anything other than full throttle max power operation dilutes the infomation left on the plug. bwalker is correct about the reading a chainsaw plug, you have to know the operating conditions just prior to inspecting the plug.

We used to refer to those (acts) as "plug chops", Paul.

At home I have a small box filled with plug chop plugs that I turned the threads off in a lathe.

Sedanman wrote:

"Warren Johnson shuts his car off with his foot to the floor and pushes the car off the track if he lacks the momentum to coast, why? Because he wants to be able to read the plugs, and anything other than full throttle max power operation dilutes the infomation left on the plug. bwalker is correct about the reading a chainsaw plug, you have to know the operating conditions just prior to inspecting the plug".

I did the same thing when racing moto-x bikes.....kill it while being held open.

Same thing on sleds...kill it at WOT to read it.

thanks bud. thats the info i was looking for.

After installing a new plug in the saw. How long does the saw have to be run before the plug will provide and accurate color reading in a chop test? Is it better to be using the saw while cutting, or can the plug be accurately read if the saw is just reved up and shutoff?

Warm it up make a cut and shut it off with the throttle held open (otherwise a strong vaccuum signal to the carb will allow a lot of fuel to wash the plug).

Sedan, Dont you mean shut the throttle off? If the throttle is held wide open certainly the reading would be distorted by fuel wash.
FWIW doing a plug chop on a saw isnt of much use. The cut and tune and tune by sound methods are better for a chainsaw.

If you close the throttle with the engine sreaming, there is high manifold vaccuum, vaccuum is what pulls fuel out of a carburetor. With the throttle pinned open and the ignition killed the engline slows to a stop without ever pulling a vaccuum on the carb. Japanese carbureted cars had a device called a throttle opener to keep the throttle from closing when the driver took their foot off the pedal to up-shift, otherwise the car would go so rich that the unburned fuel would ignite in the catalytic converter.

More fuel would be sucked into the motor with a open throttle butterfly verse a closed one. Its called a plug chop because you chop the throttle and switch the ignition off.

Ben, I know I'm right, I'm done arguing the point.

Ok.