Motorcycle Forum / General / Technical / December 2007

Thanks. That was educational. I know what the Bosch equivalent of the NGK
plugs in my Yamaha is, but I don't know if Bosch makes a platinum or iridium
*motorcycle* spark plug.

In order to use a plug that fits both cars and motorcycles, I have to be able
to screw the end cap off.

The Bosch equivalent of an NGK DP8EA-9 is WSR7E, and I would expect to find a
WSR7E with a "P" suffix if Bosch makes a platinum version, but I don't.

The Bosch site is frustrating because it won't let me search for any vehicle
except a car.

NGK came out with copper core spark plugs thirty years ago, and the copper
core is more heat stable than the old Champion steel core plugs. I could do
about two or three full throttle runs with Champions installed and my
Suzuki's engine would start shooting ducks (boom! boom!) out the exhaust, and
that could be blamed on overheating the electrode, but, once the engine
cooled down, the spark plugs were never the same, and performance was
restored by going back to NGK's.

Nippon Denso heat ranges are always three times what the NGK heat ranges are,
so if I need an ND equivalent of an NGK "8" heat range, I look for an ND "24"
heat range.

Nippon Denso seems to have beaten NGK to the concept of expanding the flame
kernel by having a
U-shaped channel in the ground electrode, and that made the ND's "Hot-U"
plugs operate like they were half a heat range hotter.

Then NGK came out with the gold-palladium spark plug that was supposed to be
like "a poor man's CDI" because the tips would get so hot they would burn
clean. That didn't work so well on a two stroke because of the lubricating
oil burning onto the insulator nose and shorting out the relatively low
"high" voltage from the small ignition coils on Japanese motorcycles.

I get annoyed when the $tealer$hip tries to charge me $2.50 for a copper core
NGK plug. I remember when I could buy American-made spark plugs for $0.65
each, but that was 30 years ago.

If you do have to pay $7.00 each for iridium or platinum plugs, the up side
is that they will last three times as long.

There are two factors in the pricing of electrical/electronic parts. One is
protectionist tariffs and the other is the fact that motorcycle distributors
and $tealer$hip$ operate like drug dealers: the price of the part gets
doubled at each point in the pyramidal operation.