Deposits on spark plug

[lbo]

I swapped out my plug today for a new one so I could take a few readings. Typically I was running kind of lean, had my main jet drilled one size higher and put on a new, bigger intake manifold.

The "new" plug looks OK to me, taken after a WOT run and hit the kill switch. Looks like a nice copper/bronze color.

little blurry


I noticed the one side of the electrode appears to be more white then the other, as well the insulator doesn't color evenly.




When I pulled my old plug (didn't do a "chop") I noticed a ton of deposits on it, and most were on the same side.

What causes this and is there anything you can tell from the plug when it's just pulled from the engine?

I run Bel-Ray Si synthetic fwiw. Could it be the ethanol blend?

The plug isn't as white as these photos show, pictures just a little over exposed. Again all the deposits gravitate and develop on the left side of the plug.

[tango]

That looks like the oil and fuel used are causing this. According to what I've seen fuel additives in particular (ethanol would qualify) could very well do this. But I've run both TC-W3 and 2T mineral and synthetic (pretty much whatever I can get, though I plan to end this practice) and I always run E10 87 octane and never seen anything like this.

Have a look at these links for more details:

motorbicycling.com/f30/spark-plug-color-chart-motorized-bicycles-24873.html

[lbo]

Thanks for the link, haven't seen that one before and very informative. From what I gather the deposits are a result of additives or poor quality fuel, and/or my plug isn't hot enough.

I use synthetic oil and buy gas at the gas pump. If I could find a gas station with seperate hoses I would go there, all have one hose where you select the grade. This means my 1.8 gallon tank is getting what the last guy before me bought no matter what I select.

I am thinking it has more to do with the ethanol added to the fuel and not sure how to circumvent this.

Should I go with a hotter plug and/or add additives to avoid this? The plug shown is only a few 1000 km old, bought it earlier this season. It also looks as though it runs rich at low RPM and lean at higher RPM's. Maybe not, but there is certainly a lot of crud that accumulates and would like to do away with that. I can only imagine what my cylinder head and pipe looks like.

[90GTVert]

I'd try a 1 step hotter plug and check/change it more often. If it's been a lot of miles on the plug with deposits, maybe just change it more often.

[bigjeff]

An occasional take it out and gently hit it with a wire brush and some electrical spray cleaner would do wonders too.

[stepthrutuner]

Aug 18, 2011 12:31:57 GMT -5 bigjeff said:

An occasional take it out and gently hit it with a wire brush and some electrical spray cleaner would do wonders too.

Some say (A.G. Bell; Two Stroke Performance Tuning) a metal brush can leave enough metal on the porcelain insulator to allow the discharge to track along that path (short out).

[stepthrutuner]

Aug 17, 2011 13:44:06 GMT -5 lbo said:

I noticed the one side of the electrode appears to be more white then the other, as well the insulator doesn't color evenly.

This is caused by the new charge coming from the upwardly aimed boost port(s) 'washing down' that side of the plug at high speed.

[ososlow]

^ ive heard that more then once too