Sparkplugs

[Assen]

HiAfter reading of people who had a sparkplug fail on their bike or car i've always felt that there had to be a reason for this failure. My idea was that a lot of people tighten the sparkplugs to much, fitted the HT-leads to heavyhanded or dropped them before fitting. But now this week, for the first time in 30 years and 750.000 miles on bikes and in cars i had a sparkplugfailure!! In my car, after 7000 troublefree miles after fitting. I first looked at al kind of other things as the cause for the rough running because the plugs were NGK's and had never failed me before. In the end it was a simple cause but completly new to me. Even the Champion plugs in my Meriden Bonnie never failed!! So you live and learn...Groet, Jannes

[FloridaMike]

Rare, but it happens. As you say, dropping a spark plug on a hard concrete floor will ruin it. This really hurts when it is a brand new $50 aircraft spark plug (but it would hurt more after takeoff). Too much anti-seize will wreck a plug as well, if you get any on the porcelain insulator, the plug is trash because anti-seize is very conductive. Overtightening usually pulls the threads out of the cylinder head because the head is aluminum and the plug body is steel. I use a new compression gasket EACH time so I don't overtighten - with practice, you can do it by hand, you really should use a torque wrench.I've seen perhaps four or five plugs bad brand new out of the box in some 50 years, and I owned a motorcycle shop some years back and we went through a LOT of spark plugs. Latest one was a bad Bosch (!) which went into my dear bride's Mazda, whereupon the car ran like crap (technical term). Swapping back the old plugs cured it, so the next day, I took all four Bosch plugs back and got Champions instead. Problem solved, wife happy.One problem I've seen is the metal covers on older BMW (motorcycle) spark plug connectors sometimes get water inside of them and they flash over, giving a conductive trail and resulting in irregular and unpredictable misfires. Removing the metal cover fixes this. Really old, thoroughly dried out and brittle spark plug wires actually glow purple in the dark! This is arcing, and is a hint that it is time for new wires.Best Regards,Florida Mike (who Irene bypassed completely on its way up north)

[Malc]

Hi Mike, Groat,Interesting you should have had new Bosch plugs fail. While maintaing a fleet of police bikes, a problem occured with the K series BMWs that was down to the new Bosch plugs fitted during a service, breaking down almost immediately, if not within the first hundred miles. This happened several times during the years I worked on them but never encountered it on the R series BMWs ( the early air cooled ones).Also, while working for a bike dealer who was main agent for the old MZ motorcycles (again, the early 2 strokes), on preparing the new bikes for the road, I had to break off the metal cover from around the plug cap as it was a known problem when they got wet.He wouldn't run to the cost of fitting a new cap!Good job Irene missed you, been watching it on the news over here.Malc