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Motorcycle guys used blasters a lot because of the carbon/lead deposits that caused the plugs to foul (especially lead in the days of leaded gasoline). Yes, you are absolutely correct that the porcelein gets a 'texture' that is detrimental to the plug. Also, 2-stroke motorcycles generally run a compression ratio of under 7:1 so your observation of failure in high compression 4-stroke engines seems reasonable. I wonder how plugs in a 9.4:1 NA wankel will react to blasting? Is this 'high compression' (I don't knoe)? Seems like a valid experiment. I have the blaster but no running rotary at the moment so this experiment will have to wait for me. BTW David, I missed you at Tracy's.
Ken Powell
-------------- Original message --------------
> My experience parallels David's. In the mid-50's when I
> started working in my daddy's service station (back when
> you could actually get FULL services from a gas station)
> one of my first jobs was to clean plugs with a sandblast
> plug cleaner like Harbor Freight sells. This was back when
> a set of plugs for a V-8 cost half a day's pay, so if
> cleaning would make 'em last another 4-5 thousand miles,
> most customers would opt for cleaning over replacement.
>
> As time went on, I learned that cleaning wasn't very
> effective on the plugs for the four-barrel V-8's, and
> we recommended against trying the cleaning option. (It's
> bad customer relations when you do a tune-up and it
> doesn't run any better - or only does so for a week or two.)
>
> Eventually, I understood that it was the high-compression
> that seemed to make the difference. Cleaning the plugs
> not only removes the deposits but it texturizes the
> surface of the porcelain. That opens the way for deposits
> to collect more quickly and provide a path for the current
> to bypass the gap.
>
> I would recommend against having "cleaned" plugs as my
> on-board spares. And use the sandblaster sparingly.
>
> Oh, yeah, and "wet" plugs. Spray 'em with brake cleaner;
> it gets oil and gas out of the cavity and leaves a dry,
> residue-free plug.
>
> Dale R.
> COZY MkIV #1254
> Ch's 4, 5 & 23 in progress.
>
> > From: "David Carter"
> > Date: 2004/11/26 Fri PM 11:44:16 EST
> > To: "Rotary motors in aircraft"
> > Subject: [FlyRotary] Spark Plug cleaners (was Re: [FlyRotary] Re:
> > Bernie Kerr had fire in the hole!
> >
> > Ken,
> >
> > I didn't see any responses to your observation about plug cleaners.
> >
> > I used to use plug cleaners all the time in 1954 Ford 6 (low 7.x to 1
> > compression ratio) and on my VW. They didn't seem to do as much good on
> > higher compression 1956 Chev'y power pack engine (8.5? to 1 "high"
> > compression) - plugs had to be good - cleaning and re-using didn't seem to
> > work well.
> >
> > Have I heard that a "cleaned used plug" is not as effective as a "new plug"
> > in the rotary engine after flooding? If there is such anecdotal info, then
> > I wonder if the "hard to start unless new plugs" is due more to loss of
> > compression due to loss of oil film and resulting need for "max good spark"?
> > I wonder if squirting some extra oil in the plug holes for each rotor face
> > wouldn't help it start better, maybe with "cleaned plugs"? Leon Prommet
> > mentioned a long time ago that an ideal engine setup would have a little
> > tank of some concoction of oil (he mentioned brake fluid??) that would be
> > allowed to drip into the intake just before shutdown to "fog" the engine
> > really good (coat parts with a robust oil film) before shutdown.
> >
> > Just wonder if "cleaned plugs" have been given a "bum rap".
> >
> > David
>
>
>
> >> Homepage: http://www.flyrotary.com/
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