Spark Plug FAQ

Compiled & edited by Kristian #562
Please read the Disclaimer before attempting any work in this FAQ.
Last Updated: 13 June 2007, by Winter #1935

Other related FAQs:


According to BMW service sheets, the spark plug(s) on the F650 should be changed every 10,000kms (6,000miles). Changing your spark plug(s) can be an easy task - it just depends on your model of bike and how easy it is to access to spark plug(s). Spark plugs can also give you an insight into the internal operation of your engine - depending on their condition. I like to keep old plugs around, and write on the packet when they were removed. That way I can check later to see if there have been any changes.

Advice: Change Plugs on a Cold Engine
Unless it is really urgent, only change the spark plug when the engine is cold. The engine case is made of aluminium, and the spark plug (where it adjoins the engine) is made of steel. Different metals expand at different rates when heated. Thus if you change your spark plug when the engine is hot, the torque you apply when installing the new plug will not be accurate. If you are performing a regular service, most people will warm the engine and remove the oil. Then they leave the bike overnight, and check valve clearances and change the spark plugs when the engine is cold.

About Spark Plugs

Spark Plug Specifications

Which Spark Plug Should I Use?

The following table lists the available spark plugs for the F650. If you are aware of a plug that is not listed, please let us know. The OEM plugs are shaded in green.

  Classic / ST
Single Spark FI
Dual Spark FI
OEM D8EA D8EA DR8EB DR8EB DR8EB usually only from BMW dealers
Platinum D8EVX D8EVX nil listed nil listed No platinum plugs listed for CS
Extended Tip ? DP8EA-9 ? ? Sometimes used for surging & stalling
problems on single spark bikes.
Extended Iridium Tip ? DPR8EIX-9 ? ?
Regular 809/RA6HC ? ? ?  
Super 8809-2/8809 ? ? ?  
Global Denso
Denso Iridium
Standard X24ES-U X24ES-U X24ESR-U+ ? Denso Iridium site states IW20 for 1997 F650
Denso websites are conflicting and confusing
Iridium IX24 IX24 IX24 ?
Bosch ? ? ? ? ? (Anyone have one of these?)

What is the Spark Plug Gap on the F650?

The Spark Plug Gap is 0.6-0.7mm. The Standard Plug is NGK D8EA or the NGK DR8EB for dual spark FI models (2004 onwards). They are preset from the factory. You can use feeler gauges to check. If your plugs are not gapped properly out of the box, the vehicle should still run fine. But, like having your valves set not-quite-right at the service interval, you would likely encounter problems down the road sooner than you would have if they'd been set right to start. Since the F650 calls for replacing the plugs every 6000 miles, it really isn't all that much of an issue.

Note: Please check the Misc Spark Plug Questions section for comments on the gap for extended tip and Iridium tip spark plugs.

Decoding NGK Spark Plugs

The following table helps to decode NGK spark plugs. Example 1 is the D8EA (12mm thread diam, temp range=8, Long thread, Special) and Example 2 is the DPREIX-9 (12mm thread diam, Projected tip, Resistor Type, temp range=8, Long thread, Iridium, 0.9mm electrode gap).

Component Value Example 1 Example 2
Thread Diameter B = 14mm
D = 12mm
C = 10mm
Hexagon C = 16mm    
Projected Firing Tip P   P
Resistor Type (Interference Protection) R   R
Heat Rating 2 = hot
12 = cold
8 8
Thread Length E = Long
H = Short
Misc S = Standard
A = Special
B = Special
IX = Iridium
- -   -
Electrode Gap 9 = 0.9mm
11 = 1.1mm

Platinum Plugs

Platinum plugs are available. NGK D8EVX Platinum. (NGK Racing: R217-9 (retail approx. $19.99))

Do Platinum Plugs make any difference?

The almost overwhelming General Consensus on the F is a resounding "No". Waste of money. They CAN however aid hard starts if you have a fouling problem, but you should look into the cause of that problem first.

Opinions on Platinum Plugs:

Split Fire Spark Plugs

Iridium Plugs

Apparently, BMW recommends Iridium for the GS. I picked up my bike from the 20 000 km service today (GS Dakar). The tech said he'd put in a Denso Iridium sparkplug. He said BMW has instructed the dealers to change to this plug when bikes are in for service, and that the OEM plugs are really not that well suited for the engine. And, yes, the bike runs appreciably better with the new plugs. More responsive, and the slight surging or stumbling I've experienced around 3.3k revs is now all but gone. They're perhaps the most expensive sparkplugs out there, but IMHO they seem to be worth it. Oyvind #1052, Norway

On one of my magneto ignition, high compression and kick-start only single cylinder bikes I had to use Champion Gold Palladium plugs. They lasted forever and the bike always started at the second kick. With "normal" plugs the beast was sometimes almost un-startable. I rode it ( on track and road) for +300 000 km so I knew how to start it. Those plugs had a center electrode that was less than half the diameter of "normal" ones. More important, the bike ran better as far as I could appreciate. I can not explain how and why but plug choice seems to be more than just heat range. Design and materials matters also. Haakon #626(Norway-F650GS)

Denso Iridium

BMW F650 97 650 IX24 0.032
BMW F650 ST 97 650 IX24 0.032

About $20, but expect that price to be significantly lower in almost any other country. I think the plug code is IX24M.

Should I install Iridium Spark Plug(s) in my bike?

Autolite Spark Plugs

Hal stated that he uses Autolite spark plugs because they have a longer reach, thereby giving him better performance. I need to verify if this is a safe thing to do? The difference in length is only .041". The gap is also in question:

  1. The NGK D8EA is supposed to be .024 to .028 inches.
  2. Autolite states a gap of .032 inches.

Resistor Plugs

What are Resistor Plugs? Well by now you might have realised that the major part of the resistance in the F Plug/Coil system is provided by the Plug Cap. Some bikes use Resistor Plugs, so another solution could be to just have a 0kohm Cap and Run Resistor Plugs in your bike, but not both!

General Spark Plug Info



General Hints

First Plug Change (spark plugs for idiots)

by Ted in TO, 01 GS

OK, so this may be just obvious stuff, but I have never dealt with plugs before, and have less mechanical experience than I would like. I decided to do a bunch of routine work on the bike last night (battery, coolant, oil, spark plug, accessory plug).

  1. While it is good to combine work on the bike, combining an oil change and a spark plug change is not a good idea. You want a warm bike to change the oil, and a cold bike to change the plug.
  2. I did the whole thing with no special tools other than those in the stock kit, but I had a h*ll of a time getting the plug socket in and turning (not enough room to work in). I recommend buying a good socket.
  3. Since I was checking the battery, I had all the plastic ripped off, and this made it easier to get to the plug (well, a bit easier). I ripped off the right hand side plastic, plus the piece that goes over the top. I then removed the snorkel and air box. This gave me access to the top of the plug.
  4. The plug itself is on top of the engine, on the right hand side, sort of sticking up and right. Look for the single thick wire that has a 90 degree bend and goes down into the engine. you will see a rubber plug with stainless around it going down into the engine. This is the plug cap. You will not be able to see the plug until you remove this.
  5. If you bought the plug already (you should have) it may have a little threaded bit on the very top. Don't worry about the threads. The spark plug cap pushes on, it does not thread on.
  6. I found the cap to be very sticky. I could sort of wiggle/twist it back and forth, but I could not pull it off, and was reluctant to really pull too hard on it in case I broke something. Keep wiggling, keep pulling and eventually it will come off.
  7. One important detail. Clean the recess (the hole where the spark plug is situated). It often (always) accumulates a lot of sand, grit and dust there, so it is a good advice to use compressed air to blow all the dirt out, before you unscrew the plug. You do not have to do it just prior to the plug change. The day before or something will be sufficient, if you keep to tarmac until the change. If you unscrew the plug with a lot of dirt in the recess, some of it will fall into the engine, NO GOOD. Some will also get stuck on the threads, NO GOOD.
  8. Once the cap comes off and you can see the top of the plug, it is pretty obvious. The big socket in the tool roll just fits neatly in there and you can unscrew the old plug. One note: the socket has two holes drilled in it so you can slot a screwdriver (or the pin provided) in there and use it to turn the socket. Unfortunately there is not enough room to turn the socket 90 degrees and use the next hole to turn another 90 degrees. So if your plug is really sticky, you have to turn as far as you can, then remove the socket from the plug and rotate it back one face (60 degrees) then use the screwdriver again. You can get 60 degrees, but not 90 degrees.
  9. Check the gap of the *new* plug before installing it, so it's within limits. I've bought some new plugs where the gap was far too wide, so it's best to check. Trevor#999
  10. Pull out the plug and pop in the new one. There is a bunch of stuff about looking at the plugs and determining stuff in the faq. I just threw out the old one. Slot the new plug in carefully. If you cross thread it, it will cost more than you can believe to get the hole re-tapped (or so I hear).
  11. Shove the plug cap back on there and put all the other bits together and you are good.
  12. Hand tighten the plug until it is finger tight, then give it another quarter turn or so. I found several figures for tightness, but the one thing everybody agreed on was that you can do more damage having it too tight rather than too loose. The spec for GS models is 20 Nm.
  13. Test the engine. If it doesn't work, bug someone else, mine worked fine. :-)

Plug Chop and How do I do it?

Plug Chops are what you do to tell which rpm range is rich or lean if you don't have an Oxygen or Gas sensor.

For Plug Reads (Colours, Descriptions)


Misc Spark Plug Questions

Will an extended tip plug cause ill/harm to my GS?

I posted the 2-part spark plug question, and I have since gone to the store and purchased a Standard Projected Tip--NGK DP8EA-9. You guys are sure my bike is not going to suffer any ill harm in using this plug? I know (or read) in the FAQs that it works well. Can you give me a few additional words of faith? billmallin #1629

What gap should I use on an extended tip plug?

Also, the gap. I read in the FAQs that they come pre-gapped, but (since I am an engineer) can you tell me what the gap should be for this extended-tip plug? billmallin #1629

What gap should I use on a Iridium plug?

Hello everybody! I was reading thru the FAQ's and have decided that I will replace my spark plug (I am close to 6K miles) with an iridium plug. Based on the specs. I see that the factory gap is .6 and that the Denso iridium gap is set at .32 > Is this the wrong plug?? Which one should I use? pulixer

My new plugs do not come with a screw-on terminal/cap

I just received a couple of the iridium plugs that I ordered through the net (couldn't find them locally). Like the other projected tip plug from NGK, they also do not come with a screw-on terminal/cap. I'm assuming that I can take the cap off of the plug currently installed on my bike and put it on the iridium plug. Is my assumption correct? Otherwise, I have to go out and locate some caps. JC12

NGK Plugs in Canada

BTW, if anyone is having problems finding these plugs up here in Canada I found a solution. I went to a major parts supplier (Lordco Auto Parts) with the NGK iridium part numbers and they could not find the listing in the NGK catalogue. Even the Manager was looking at the latest book but they did not show up as available in Canada. He said he would have to order them direct and couldn't do that at less than 100 units!! Well we finally found 'em by looking at applications rather than the NGK part numbers and cross references. If you pick up the newest NGK catalogue and look under Cagiva Elefant it lists the plug there. Using the Lordco Part #'s I ordered 4 Iridium NGK's for a Cagive Elefant and got 4 nice new DPR8EIX9 iridium plugs. I know, it should be easier. Who knows why the listing is so stupid and why is there no reference elsewhere? No matter, plugs are in and it's time to go for a road test to see if there is any difference at all for a new Twin-Spark. Bario

Any hints on accessing the spark plugs?

Any hints on removing the plugs on a GS without removing the airbox?

Is there any known way to remove/install the spark plug without having to remove the snorkel and air box (as is explained in the FAQ). I was hoping a deep socket could do the job without even dissasembling the bike. Any Ideas? pulixer

My spark plug appears to have corroded

There have been reports of older (pre fuel injected models) bikes having corroded spark plugs / caused by the plug caps. Please check the Plug Caps and Coils FAQ for more information.

Leading causes of dry spark plug fouling, as indicated by dry, black, sooty residue. (NOTE: Not "wet" fouling)

In my search for wisdom regarding fouled plugs I have plowed through the faq, NGK's spark plug guide, and too many Google searches to count. After reading acres of verbiage, and sifting our the contradictory data, here is what I have boiled it down to: (robert in TX #959)

  1. Too "cold" of a spark plug, resulting in the plug operating at a non-self-cleaning temperature.
  2. Too rich of a mixture.
  3. Excessive idling (including stop-and-go driving).
  4. Retarded timing. -- robert in TX #959
  5. Crap Beru spark plug caps allowing intermittant firing. (They allow plugs to wet-foul when they're totally dead) Flash 412 (CO)
  6. If you have a sick oil burning donk, then the plug will oil foul. The solution is a re-ring and cyl hone and/or valve guide job for a permanent fix. Otherwise go 2 grades hotter than recommended for spark plug, this will keep oil deposits burnt off the plug tip. Keep pouring oil in to the engine, so it does not run low. IF you run hard miles like this, you COULD bash a hole in the piston, but it will probably run out of oil first! jack

DPR9EIX-9 instead of the DPR8EIX-9?

So, I'm reading that the Denso IX24 is the better plug for the GS for many reasons. Problem is...that particular plug is difficult to come by locally. However, many shops offer the NGK DPR9EIX-9 instead of the DPR8EIX-9, the 8 being the exact equivalent and the 9 being slightly different with regard to temperature? The guy on the phone said it was a little cooler but should work. I also read of some people using the 9, but no followup...which is probably a good thing. rob feature

Intercom noise after spark plug change?

Intercom noise is sometimes caused by RF noise. The RF noise can be generated by spark plugs / plug caps with no resistors. Take a look at the table below... If you replace the plug caps on the earlier models with a non-resistor type plug cap, you may experience noise. If you replace the spark plugs on later models with a non-resistor spark plug, you may experience noise... In other words: either your spark plugs or plug caps should be a resistor type.

Year model Plug Caps Spark Plugs Result
1994 - 2003 Resistor Non-Resistor No noise
2004 onwards Non-Resistor Resistor No noise
All models Non-Resistor Non-Resistor RF Noise possible

Where can I find a supplier for the NGK DR8EB?

I have a Dual Spark - How would I know if one was not working?

What spark plug cap do I use on my FI model bike?