The Difference in Spark Plugs?

[beemrdon]

Hey folks,

I have been using plain jane NGK spark plugs in my K1100 since I've owned it. Changed them not that long ago but the old ones were REALLY toast after about 25,ooo miles.

Question is...would iridium plugs give substantially longer life?   

My Toyota Sienna van has almost 130,000 miles on it with the original iridium plugs and runs fine...(note: will be changing them out shortly - (PITA v6 placed sideways in engine compartment).

Probably not going to get that kind of miles with the K but curious if going with iridium will make a substantial difference in change intervals.

Thanks

[Martin]

Standard NGK in OZ is around $6.00 AU NGK iridium is around $20-25.00ea. BMW recommends changing plugs every major service 10,000 miles (15,000 Km's). I change mine every 20,000 Km's and they still have heaps of life in them. NGK recommends 20,000-40,000 Km's changeover for standard plugs and 60,000 Km's for iridium. So going on their recommendations cheaper to stick to standard plugs.
Regards Martin.

[Scott_]

Also keep in mind when manufacturers make "mileage recommendations" they are thinking of a standard car engine that sparks the plugs only 1 time per engine revolution....But our brick engines use a "wasted spark" technology......that means our plugs spark 2x per engine revolution.... We should only expect 1/2 of the published mileage recommendations with our brick engines.

Just my opinion, your mileage may vary.

[beemrdon]

Any iridium users want to chime in?

[Scott_]

I bought 8 of the NGK DR7EIX iridium's in 2010 for both bikes. For some reason I only installed them in 1 bike. (I've still got 4 new in the box)
In 2015 I bought the standard XR5DC Bosch plugs for both bikes.

Can't say why I went back to the standard plugs, the price point wasn't that different. $7.40 each for the NGK in 2010, $6.21 each for the Bosch in 2015.
I've still got the old ones that came out(don't ask me why) and they look to be well worn.

[The Mighty Gryphon]

The main reason for changing spark plugs is the widening spark gap caused by erosion of the center electrode.

I always check the gaps when I install new plugs and again when I replace them.  The NGK plugs in my bikes show some wear of about .003-.005" over 20,000 miles.  That is not enough to inhibit a good spark so every other year(about 15,000-18,000 miles) I change mine.  At less than $4 each, they aren't a major maintenance expense.

I can't see any reason to use anything else.

[beemrdon]

"I can't see any reason to use anything else."

I'm looking for loooooooooonger change intervals.

[The Mighty Gryphon]

The NGK plugs will go a lot longer, easily 30,000-40,000 miles at the erosion rates I've seen.  I just change mine every other year because they're fairly inexpensive and when it's dark and I'm out in the middle of nowhere Iit's nice to be able to think about other things. 

There's nothing wrong with the rare earth plugs, I just have a hard time dropping $40+ for a handful of spark plugs   They don't save me any labor because every year I pull my plugs and check the gaps anyway.

[beemrdon]

Hi Gryph, .......................The last time I changed the plugs, one of the stock wires fell apart at the head so I ended up buying an NGK wire set for the price of 1 Beru wire. The NGK wires that I bought are some kind of plastic and don't seem very durable, unlike the NGK set that I bought for my R90/6, years ago.
So my thinking was to not disturb them any more than necessary.  As I stated above, the iridium plugs in my Sienna van are 130,000 miles old now and are still working (Toyota recommends changing them at 120,000 miles), so I got to thinking about longer life plugs for the K.
The purpose of my starting this post was to hear from any users of iridium plugs to get an idea of their longevity in the K motor application. Seems like no one uses them.

[K1300S]

Have you pulled and looked at the plugs in your Toyota?  The iridium plugs in my BMW 325 were gone by 60k miles.  And I mean gone.... No electrode left.

[The Mighty Gryphon]

I can't speak to motorcycles, but around the early 1980's the EPA mandated that vehicles manufactured in the 1987 model year and later were to maintain emissions and fuel economy for a period of 100,000 miles with no owner intervention(ie. tuneups).

This pretty much meant that outside of oil changes, the owner needed to do NOTHING to maintain the engine in their vehicle.   To achieve that, manufacturers had to use computer controlled fuel injection and spark ignition systems. 

The spark ignition systems were designed around rare earth electrode spark plugs and variable voltage electrical systems for the spark.  The variable voltage was to reduce electrode erosion while still providing enough spark to cause combustion. 

I don't think motorcycles were included until I got out of the business, so I don't know when or how spark systems were incorporated on bikes.  I am pretty sure that with the plugs BMW recommends for the K bikes and the service intervals, their spark systems are fairly low tech and won't provide the same electrode life as found in modern automobile engines regardless of electrode material. 

My experience is that K bike engines aren't terribly hard on spark plugs, so changing a set of plugs every 20,000 miles is no big deal when they only cost $3-4 each.