Fouled plug

My local Napa steered me towards NGK plugs.  They stopped carrying Autolite plugs because thy had been getting a lot of complaints about their quality.

The 295 is a copper core (non resistor) plug... so in conjunction with solid-core wires, an appropriate choice for magneto applications.

Regarding price, quantify 'high priced'... I'm seeing them falling in the $3/plug range... up to $20 for a box of four (so $5.00 a plug)... I don't see that as being far out... if you're seeing a box of 8 for $40, then you've got enough to do TWO tractors...

The reason why I don't use Champions, is simply because I experienced a catastrophic failure of one plug, that destroyed an engine.  The crimp failed, and compression ejected MOST of the electrode's ceramic insulator out the plug hole, but the rest wedged against the piston and opened up the cylinder wall like a zipper.  It cost me just over $10,000 to replace the power in my boat, and Champion was unwilling to lift a finger to repair the mess.  They offered me a replacement spark plug.

After discussing the failure with over two dozen well-experienced automotive technicians, and being told that crimp failures were a common story for the brand, I started testing everything I had which had a spark plug, and found that basically all but one that had a Champion plug, leaked compression through the crimp of at least 30% of the plugs.  I replaced them all with other brands, retested for leaks (WD40 on the crimp while running just off idle will usually show bubbles when there's a leak) and found none... and they all ran better.

One thing to consider-  if the engine is missing on just one cylinder, spray some WD-40 on the plug crimp and look for bubbles.  If it's leaking, change THAT plug, and try again.  If it stops missing, and you have no more leak, you found your problem.

Seems like a lot of people are overlooking something here. What's causing the fouling? Is it oil? Fuel? Poor Ignition? Timing off? A lot of these issues cause a plug to foul one way or the other. Yeah, heat has a lot to do with engine performance and operation, but all the other variables that I mentioned about have to be taken into consideration. Is the plug fouled with oil? If so, you need to look into where the loss of oil control is. Maybe valve guides. Maybe the engine needs a valve job. Possibly rings. A tired worn out engine can foul plugs all day. Low compression. These engines already have low compression, Now its even lower cause it's tired. How bout' a high float? Hey, that'll foul not only one plug but maybe two. What I'm getting at here is just throwing in a certain mfr's plug ain't gonna cut it if there is a problem causing it. I always tell my customer's, if you use a certain mfrs spark plug and have good luck with it, there might not be anything wrong with the engine causing the fouling because the engine has been running great. On the other hand, you can go through 6 different types of plugs and still have the fouling issue. Gotta' get to the root cause of why the fouling occurs. Once you found the culprit, you can select a certain heat range of plug that works the best in that particular engine. And remember, engines are like people, they all operate differently from one another, so one type of plug may work in one 125 or 226 engine, and that same plug may not work as well in another of the same size and type..... HTH

Steve@B&B