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Old 18 January 2008, 14:42   #11
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Yep, I've had them fail too, especially in air cooled engines. But spark plugs do seem to get tired, even after a proper sand blast clean, truing the electrodes and gapping them they may not perform well. Dunno why.
Don't ever sandblast plugs or even use a wire brush on most modern plugs . Only solvent should be used .
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Old 18 January 2008, 14:50   #12
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Don't ever sandblast plugs ..
Why?
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Old 18 January 2008, 16:44   #13
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sandblasting can force tiny particles of sand betwen the electrode and the insulator and into the body of the plug . When it gets hot the sand expands and cracks the insulator or causes hot spots which lead to plug failure .

The fine elecrtodes of modern platinum plugs etc are easily damaged even by wire brushing
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Old 18 January 2008, 19:46   #14
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Don't ever sandblast plugs or even use a wire brush on most modern plugs . Only solvent should be used .
Ian, what solvent do you use or recommnd for cleaning.

Have benn cleaning plugs with Acrylic Thinner for years with excellent results. Dip/soke the plug electrode and all thread height for 30 secs in a small container, remove, with a cotton moistned in thinner clean the thread, electrode, dry well, regap and tight again. You can take a wooden/plastic shushi stick and make yourself a big cotton swamp, damp with thinner and clean well in circles the cylinder head thread. Will look like brand new.

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Old 18 January 2008, 19:56   #15
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Ian, what solvent do you use or recommnd for cleaning.

Have benn cleaning plugs with Acrylic Thinner for years with excellent results. Dip/soke the plug electrode and all the extension of the thread for 30 secs in a small container, with a cotton moistned in thinner clean the thread, electrode, dry well, regap and tight again. You can take a wooden/plastic shushi stick and make yourself a big cotton swamp, damp with thinner and clean well in circles the cylinder head thread. Will look like brand new.

Happy Boating
Thinners is ok I guess , i usually grab a tin of carb cleaner spray , which smells just like thinners .
Petrol is always to hand I suppose that would sort an oily plug .

I haven't seen an oiled plug for years but i used to clean them in petrol then burn it off with a lighter , a warm plug used to help if you could get it back in quick enough . I don't miss those days really.
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Old 19 January 2008, 07:45   #16
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Ribnet readers will appreciate to read how a theorically simple item can give you really unpredictable bad times. I usually recommend clients if excesive idle operation is done to wot their engines al least for 1 minute once in a while to help plugs clean themselves and avoid plug foulling and short circuits.
I always try and have a short blast at WOT as late as I can before I take the boat out of the water - I figure that if the plugs are clean it will start better the next time I use it, and my engine is prone to fouling one plug all the time anyway (not sure why)
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Old 19 January 2008, 09:00   #17
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I always try and have a short blast at WOT as late as I can before I take the boat out of the water - I figure that if the plugs are clean it will start better the next time I use it, and my engine is prone to fouling one plug all the time anyway (not sure why)
Yes, sometimes wot (2 stroke engines) before taking the boat out until the engine stops out of gas, specially if don't know when will be the next go out. Iy you are a person that removes engines from small boats and lays engine inside car trunks will definitely avoid the gas/oil spillage inside. Your carpet will appreciate it the most...

From all years cleaning spark plugs, have noticed that the lower plug always tend to foul more than the upper in 2 cylinders 2 strokes engines. That's why in the next cleaning session are regaped and rotated to the opposite cylinder. Have given me better plug life span between changes and probably avoid shorts on plugs.

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