Spark plug life

[BrianM]

I am wondering how many miles before most are changing plugs.

 

I have 12,000 miles and the plugs are at the service limit - 1 mm gap.

 

[Highway41]

Might be overkill, especially at BMW prices, but every 12K miles for me.

Bill

[dirtrider]

Afternoon Brian

 

Using miles to determine spark plug change interval is BMW's guesstimate on (average) spark plug life.

 

It really boils down to how may sparks across the electrode gap, duration of spark, with a bit of spark intensity stirred in.

 

If you run around in 1st or second gear at higher RPM's with few miles traveled, or LOTS of idling then spark plug change-out would probably be earlier (miles wise) than if you ran continuously in 6th gear at 60 mph with few stops & little idling.

 

Probably more accurately would be using running hours on the plugs but the BMW has no hour meter to go by.

 

12K seems early for an average rider to have attained both electrodes to be at max.

 

I have only installed a few sets of MAR8B-JDS plugs so far (none mine) & initial gap on one set came new at a tight .9 mm so those would have gone less miles (hours) to max gap. (I re-set them to .8 mm before installing)

 

You really have no idea on what the original gap was so maybe your plugs were a bit wide to begin with, I doubt BMW personal check the electrode gap at engine build. Probably just a quick visual for damage then plop them in.

 

Those MAR8B-JDS are fairly expensive & so far not much matches up from aftermarket. At least the price is starting to come down a bit on SparkPlug.com & E-Bay.

 

[terryofperry]

Oreilly's can get them.

 

http://www.oreillyauto.com/site/c/detail/NGK0/8765.oap?ck=Search_8765_-1_2491&keyword=8765

 

Terry

[MikeB60]

I cleaned my up at 12,000 miles, reset the gap, and re installed. Bike runs great so I figure I would change out at 18,000.

[David R]

With how the bike runs, and how they look, I plan on one set for the bike. The ford trucks I take care of make up to 130,000 miles on an original set. Sparks are sparks. As long as they look good.

 

When is the last time anyone has a post that ended up being a spark plug?

 

I switched the uppers for the lowers at 6,000 miles. Probably do it again at 12,000 etc.

 

To each his own. or Your mileage may vary.

[dirtrider]

Evening Dave

 

 

It's not so much about the spark plug itself or how the engine runs. The engine would probably run (idle) even better with a 1.5mm electrode gap. Most lean burn engines operate better with a wider spark plug electrode gap as that produces a fatter spark.

 

It’s more about protecting the stick coils. As the plug electrode gap starts getting wide then the coil's KV starts increasing & that can cause internal coil arcing as well as extra coil heat when engine loading increases the KV required to jump the larger gap.

 

If you have ever cut a BMW stick coil open you will see those things are a very thin design so the RFI shielding it pretty darn close to the windings.

 

BMW stick coils are already marginal so why push them harder than design intent. Plugs are a lot cheaper than coils.

 

[Danny caddyshack Noonan]

It’s more about protecting the stick coils. As the plug electrode gap starts getting wide then the coil's KV starts increasing & that can cause internal coil arcing as well as extra coil heat when engine loading increases the KV required to jump the larger gap.

 

Dirtrider, that makes the perfect amount of sense. Dielectric breakdown. Some house electricians, I've been told, call it the smoke test on new build. We do electronic assy's at about 500V looking and listening for arcs. However, you can test to failure by breaking down the dielectric or, insulation.

[David R]

You folks do as you wish.

 

I have seen more stick coils go bad than spark plugs. Even on those ford vans. If they come in with a misfire, I replace the coil and plug in that cylinder and out the door it goes trouble free until the next adventure. MOST don't even come in for that.

 

Dirtrider, If the plug has the proper gap, what else can go bad that would take the coil with it?

 

My Airhead will foul the plugs after a while (a few years) from burnt fuel and oil.

 

My 1100RT did not do that. I tried the gimmick spark plugs and once I switched to the 3923 they stayed in there until I rebuilt the motor and put in a fresh set. That was 30,000+ miles.

 

I expect to get the same results on the camhead I think BMW should say INSPECT at 12,000 miles. This is a brand new motor.

 

This camhead does idle lean, but the end of the muffler is black which tells me its not running so lean. That and fuel mileage is in the mid to low 40s (mpg). Lower plugs are darker than the uppers. I think the bike is getting the proper amount of fuel.

 

Yes, High Temp and full load tests the stick coils. Its harder to make a spark in a lean engine especially under full load, This is the coils job The spark plug is the messenger. As long as the spark HAS to jump the gap and cannot short to ground any other way, I think the spark plug is doing its job. This is assuming the gap and torque are within spec.

 

David

[dirtrider]

----Dirtrider, If the plug has the proper gap, what else can go bad that would take the coil with it?

 

----

 

 

Morning David

 

 

That's the secret, proper electrode gap. Obviously the OP here has seen his electrode gap go to max in 12K. Assuming the plugs were within spec at engine build that would be .1mm growth per 6K of his riding so at 24K the electrode gap would be 1.2mm (or more as the spark gets hasher at extended electrode gap). As the plug electrodes wear the nice sharp edges are rounded & that pushes the KV required from the coil even higher.

 

 

 

Your 1100 didn't have stick coils, that system uses a conventional lost spark coil & long spark plug wires. There is no coil inner RFI shielding for the spark to arc to.

 

The BMW OEM camhead spark plugs are not exotic electrode long life plugs like a lot of modern autos/light trucks use so they are not 100K plugs.

 

Camhead riders will just have to decide if they want to abide by BMW recommendations on spark plug replacement, or attempt a re-gap at around 1mm electrode gap or, try to squeeze more miles out of the plugs at the risk of coil stress.

 

[tallman]

Thank you DR.

 

yada yada

 

Obviously YMMV.

 

 

[RTinNC]

Might be overkill, especially at BMW prices, but every 12K miles for me.

Bill

 

+1 .... why make things difficult.

[BrianM]

Looked closer at the plugs. The center electrode has worn flat across from the two side electrodes.

 

I am going to buy some new plugs, set the gap towards the lower spec (0.07mm) and see how long they last.

[dirtrider]

Morning Brian

 

That is a good idea. If you start with a KNOWN spec to begin with then measure again in 10K-12K you will get a good idea on the electrode gap growth per mile for your riding usage.

 

I have seen that same flattening of the center electrode on the OEM 1200 hexhead plugs but usually at a much higher mileage than you are at now.

 

Hopefully in the future there will be a suitable replacement plug that uses exotic metal electrodes that will last longer than the OEM plug does.

 

[tsp]

I waited too long to replace mine. When I had my valves checked at 24,000 miles I was told that the plugs looked good on my 2010 RT. I decided to change them myself at 30,000 miles. There was a marked difference between my old plugs and the new plugs. I'm planning on changing mine every 18 or 20 K miles.

 

tsp

My MC Blog

[Dave_in_TX]

Hopefully in the future there will be a suitable replacement plug that uses exotic metal electrodes that will last longer than the OEM plug does.

 

It looks like the Denso IU24A may be a possibility. Not sure why it doesn't show up when running a cross reference check. Maybe it's the slightly different hex size (doesn't look like enough to be significant).

http://www.sparkplugs.com/product.aspx?zpid=11217

[Guest Kakugo]

Hopefully in the future there will be a suitable replacement plug that uses exotic metal electrodes that will last longer than the OEM plug does.

 

It looks like the Denso IU24A may be a possibility. Not sure why it doesn't show up when running a cross reference check. Maybe it's the slightly different hex size (doesn't look like enough to be significant).

http://www.sparkplugs.com/product.aspx?zpid=11217

 

Hi Dave. According to Denso the correct iridium plug for the RT is the IXU24. However it comes with a very tight gap (0,8mm). It's the same plug they recommend for the last six cylinder M3.

[terryofperry]

Dave and Kakugo

 

Could you point me in the right direction with a Denso website showing any Denso plug for the Camhead? I cannot find it on any of their sites, USA, Europe, Japan, etc. I also cannot find a Denso cross for the NGK Mar plug.

 

Thanks

 

Terry

[Dave_in_TX]

Hopefully in the future there will be a suitable replacement plug that uses exotic metal electrodes that will last longer than the OEM plug does.

 

It looks like the Denso IU24A may be a possibility. Not sure why it doesn't show up when running a cross reference check. Maybe it's the slightly different hex size (doesn't look like enough to be significant).

http://www.sparkplugs.com/product.aspx?zpid=11217

 

Hi Dave. According to Denso the correct iridium plug for the RT is the IXU24. However it comes with a very tight gap (0,8mm). It's the same plug they recommend for the last six cylinder M3.

 

Kakugo, this discussion is for camhead engines. The IX24U will not fit the 2010 or later camheads. It will however, fit the 2009 or earlier hexheads.

[Guest Kakugo]

Then I guess it's time to toss away that old Denso catalog and get a new one.

[Dave_in_TX]

Then I guess it's time to toss away that old Denso catalog and get a new one.

 

Either that or don't buy a new RT.

[Guest Kakugo]

Then I guess it's time to toss away that old Denso catalog and get a new one.

 

Either that or don't buy a new RT.

 

I'll wait until the Waterhead comes out to make up my mind, thank you.

[Dave_in_TX]

I am going to buy some new plugs, set the gap towards the lower spec (0.07mm) and see how long they last.

 

I have a set of new plugs ready to go in. The factory gap appears to be 0.08mm. I was going to regap them to 0.07mm but my gapping tools won't work on such a small plug

[Bob_Minor]

That should be 0.8mm.

[Dave_in_TX]

That should be 0.8mm.

 

Yes, that's what I meant to type

[lkchris]

Here's Euromotoelectric's page on these plugs

 

http://www.euromotoelectrics.com/SearchResults.asp?Search=MAR8BJDS+

 

A LOT of the description given there conflicts with statements above.

[Dave_in_TX]

Here's Euromotoelectric's page on these plugs

 

http://www.euromotoelectrics.com/SearchResults.asp?Search=MAR8BJDS+

 

A LOT of the description given there conflicts with statements above.

 

 

I don't see much at that link that conflicts with previous postings

[lkchris]

Here's Euromotoelectric's page on these plugs

 

http://www.euromotoelectrics.com/SearchResults.asp?Search=MAR8BJDS+

 

A LOT of the description given there conflicts with statements above.

 

 

I don't see much at that link that conflicts with previous postings

 

Yep, after I posted I noted errors and emailed and it was all changed.

[RTJohn]

So I just tried to buy four plugs from Oreilly's. No luck. They were out and didn't know when they would be getting any more. Also, there's a $6 shipping charge if they did have them. Anyway, know of any place other than the dealer to get these NGK's?

[Dave_in_TX]

So I just tried to buy four plugs from Oreilly's. No luck. They were out and didn't know when they would be getting any more. Also, there's a $6 shipping charge if they did have them. Anyway, know of any place other than the dealer to get these NGK's?

 

Try sparkplugs.com

[dirtrider]

Morning John

 

Usually E-Bay has them for around $50.00 for set of 4 (free shipping) but nothing there right now. (must be the usual spring mark up season)

 

 

If you go to Sparkplug.com then try this code for 10% off (maybe??, it worked a few weeks ago for me)

 

Try coupon code 11TOYN100F

 

Also Beemer Boneyard has them with a discount at the moment.

 

[RTJohn]

Thanks DR. Your coupon was invalid but I went ahead and purchased 4 of them. It came out to $14.31 each including tax & shipping. Still cheaper than the dealer by several dollars.

[terryofperry]

NAPA, but you will pay.

 

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=NGK8765_0381397708

 

Terry

[macx]

Beemer Boneyard has a set for about $60.

 

Hope somebody comes out with an "exotic" metal plug!

 

 

[Dave_in_TX]

Beemer Boneyard has a set for about $60.

 

Hope somebody comes out with an "exotic" metal plug!

 

Someone on the BMWMOA site thinks they have:

"The plug I am running in my 2010 RT i

a NGK "CR9EKPA" stock #7785 the caveat is it only comes with 4mm threads on the coil end of the plug i just purchased 4 mm spark plug terminal nuts and they work fine. I changed out my original stock plugs @ 11k they were in rough shape, I have just under 13K on the new set and they look good. they are platinum tipped and they are no cheaper than the stock plugs but you can get them at napa."

 

The CR9EKPA is one heat range colder than the stock plug. Using the cross reference at sparkplugs.com, the hotter CR8EKPA cross references to the Denso IU24A iridium plug. The CR8EKPA cross references to the IU27A. So there may be two alternative plugs.

[tsp]

I went 32,000 miles with my plugs. That's a mistake!

I couldn't post a picture of the plugs (photo was too large) but you can see a picture on my blog page here;

http://www.airheadmoto.com/2013/03/spark-plugs-and-motorcycles.html

 

 

tsp

 

[David R]

You said it your self in the article. Bike was running fine.

 

No adjustable gap in those plugs.

 

I plan to see how long they will run in my 2112 R1200R. I inspect them every 6,000 miles. I don't plan on changing them for a long time. I switch the uppers for the lowers upon inspection.

 

David

[Dave_in_TX]

You said it your self in the article. Bike was running fine.

 

No adjustable gap in those plugs.

 

I plan to see how long they will run in my 2112 R1200R. I inspect them every 6,000 miles. I don't plan on changing them for a long time. I switch the uppers for the lowers upon inspection.

David

 

As DR noted in this thread, the bike may continue to run fine but the excessive gap puts extra electrical stress on the coils.