how do these plugs look?

[llahbocaj]

Today I replaced my spark plugs as part of my 24k service. This is the first time I've replaced the plugs, a dealer did the 12k service while I was on the road so I'm not sure what the plugs are supposed to look like.

I'm wondering if this is what would be considered normal wear.

2004 dual spark bike. Primary plugs on the left, secondary on the right.

If I didn't know any better I'd think that the dealer forgot to replace the secondary plugs at the 12k service but I'm sure there's a more logical explanation about the secondary plugs firing during the exhaust stroke something or another...

Pictures:

[mwelker]

I think they look fine. Dry, with little wear on the electrode. I would still change them for a few bucks.

[combustor777]

Any documented advantage to the dual spark? seems like more of a pain than anything with the stick coils going bad and twice as many plugs to fool with.

[llahbocaj]

Any documented advantage to the dual spark? seems like more of a pain than anything with the stick coils going bad and twice as many plugs to fool with.

Documented advantage? Dunno.

From reading through this forum and ADV I've seen it suggested the dual spark makes for cleaner emissions and that it helped address the surging problems that seemed to have plagued BMW's of this era. Whether that's all snake oil patent medicine or not I don't know. This is the only other BMW i've ridden besides my /5 and it's never surged unless I get choppy on the throttle when it's barely cracked open, but the PO also pulled the motronic coding chip, which I've also read was in attempt to reduce the surging.

My initial curiosity was why the secondary plugs look so much more banged up than the primary ones.

Changing all four plugs took maybe 10 minutes. I've read that a lot of peoples coils are starting to fail right around the same mileage my bike is at so I've considered replacing them in an act of preventative maintenance. Better now while I can get the parts online for cheap than when I'm on the side of the road away from home and have to wait for the dealer to get the part and then charge me list price.

[mcollect]

I don't know if I would change them yet. But if youbuy them stick them in your cases with all the things we carry just in case. When you go to sell you can sell them separately. Like all the other spares we carry, it seems if you carry emergency parts you never need them.

[iowabeakster]

Everybody seems to question the condition of the secondary plugs when they get changed. Mine looked the same as yours, and ours look the same as the others who have posted pictures.

As the phrase goes...they all look like that.

[towerworker]

I have changed my plugs a few times (dual spark) and the secondary plugs pretty much always look a tad fouled compared to the primary. Possibly they get more oil that sits on them after shutdown.

[boxermania]

Leaving the details aside.......

The primary plugs look good.....that is the way (color) the porcelain should look. Although, for a real read you have to look down into the plug.

The secondary plugs look like they have endured significant heat.....the porcelain is brownish and all the threads are of the same color. Normally three or four threads will show any semblance of color, like the primary plugs.

Last but not least, seeing two diferent plug brands lends credence to your suspicion that the secondaries might not have been changed.....they also show a bit more wear at the center electrode.

Personally, I would go with the Autolites 3923P, single electrode for the primaries at .030" to.032" gap and a comparable for the secondaries but one heat range colder(so it transfers more heat to the surroundings)

Good luck and let us know the outcome.

[boxermania]

Forgot....

The secondaries have one thing against them.......they have a smaller diameter which means less area to transfer heat to the surroundings.

The other thing I don't know (mine was a singe plug) is if both plugs fire at the same time......which I doubt as the idea is to insure complete combustion (as complete as possible).

So if the secondaries fire slightly past the primaries they will be seing a rise in temperature higher (flame front) than the primaries which they have to dispose off......

Of curse that is if my hypothesis holds.......

[Biff's R]

With a dual plug bike, it will still run with only the secondary plug firing. It just won't run as smooth. I would not swap out a stick coil unless it has failed. If you want to buy an extra one for an extended trip, that is ok, but why spend $250 on parts that you may never need?

I have had both the dual spark and the single spark, and I could not tell a performance difference. It is just an extra set of plugs you have to buy, and maybe a little lower emissions.

[towerworker]

Al,

You mention a plug gap of .030 to .032. What is your opinion or knowledge of variances of plug gaps? I have been running .034 to .035 on both primary and secondary plugs with seeming ok results. Your thoughts?

Wayne

[llahbocaj]

The two different plug brands are standard for the bike:

12127653771 - spark plug (BKR7EKC M14)...NGK
12127681415 - spark plug (YR6LDE M12)...Bosch

I'll look into the Autolites the next time around but I already had replacement NGK and Bosch plugs for this service.

Re: preemptive coil replacement...it seems to be an established problem and would just be one less thing to consider when I'm on the road, carrying a spare doesn't sound like the worst idea ever but how many spares can you really carry on a bike before it becomes absurd? Did I really just ask that question?

The consensus seems to be a standard "they all do that" which I am more than comfortable with and pretty much what I was hoping to get. I'd never replaced plugs on this bike myself and I was just looking for a baseline.

Leaving the details aside.......

The primary plugs look good.....that is the way (color) the porcelain should look. Although, for a real read you have to look down into the plug.

The secondary plugs look like they have endured significant heat.....the porcelain is brownish and all the threads are of the same color. Normally three or four threads will show any semblance of color, like the primary plugs.

Last but not least, seeing two diferent plug brands lends credence to your suspicion that the secondaries might not have been changed.....they also show a bit more wear at the center electrode.

Personally, I would go with the Autolites 3923P, single electrode for the primaries at .030" to.032" gap and a comparable for the secondaries but one heat range colder(so it transfers more heat to the surroundings)

Good luck and let us know the outcome.

[llahbocaj]

As an edit...I checked my records and these plugs actually only have 8k on them as I did my 12k service a little late and am doing my 24k service a little early because I plan on being on the road when the bike turns 24k. I now wonder (a little more than I did before) if the dealer that did the 12k (actually mileage 15k) service didn't replace the secondary plugs and they have been running since 6k. It's almost a moot point as this bike was new to me with 8k last spring so either way it's been ~1 year on the plugs, just something to wonder about.

[iowabeakster]

If you order a set of plugs at the dealer or beemerboneyard you will receive the mismatched brands. I speculate the biazzro reasoning from the factory is that the mismatched branded plugs use the same sized socket wrench.

here I will quote mad1150:

As everyone here probably knows, or may find out the hard way, the Auto-Lite 4164�s are a replacement for the bottom plugs on the twin-spark models. However, they won�t fit in the standard BMW plug wrench and to make matters worse, a standard 11/16� deep socket that fits the plug will not fit up into the plug well of the engine.

Here's the whole thread with Mark's solution. My solution was to stick with stock...because I have a dealer in town...or was ordering other parts from beemer boneyard anyway.
viewtopic.php?f=8&t=16411&start=0

[boxermania]

Wayne

The .030" to .032" is what I liked with the mods on my bike. Really, there isn't much difference to the .034" to .035" you use.

I'm somewhat anal about gapping plugs and one interesting thing to know is that gaps increase by ~ .001" per 1000 miles. So with a good initial gap one can determine how many miles the engine has run.....for what is worth.

[MattPie]

Wayne

The .030" to .032" is what I liked with the mods on my bike. Really, there isn't much difference to the .034" to .035" you use.

I'm somewhat anal about gapping plugs and one interesting thing to know is that gaps increase by ~ .001" per 1000 miles. So with a good initial gap one can determine how many miles the engine has run.....for what is worth.

Question: how does one gap plugs that are designed like the pictures above? I'm fairly certain a normal flat feeler won't work since the gap is curved.

[llahbocaj]

I wondered the same thing when I got the plugs and after looking through a few manufacturers websites it seems that the dual electrode plugs are sold pre-gapped from the factory. I couldn't even check the gaps with my old-fashioned gapper so I'm hoping they're correct.

Question: how does one gap plugs that are designed like the pictures above? I'm fairly certain a normal flat feeler won't work since the gap is curved.

[NoRRmad]

There are "gap feelers" that use wire probes. You swing out a wire of the correct diameter and slide it into the curved gap.

[boxermania]

Multigap plugs are typically gapped at the factory.....unless they have been dropped........