Hi guys, I am probably opening up a can of worms here but does anyone recommend a spark plug other than standard. I think Bosch X5DC are the norm and the ones I have in are XR5DC and while I am aware the main difference is the "R" is for suppression of excess electrical noise is there any noticeable difference in performance as the originals are a bit hard to find.

Regards,

Phil Mars

Hi Phil,
I am a fan of Denso Iridium plugs for two reasons they have a very small electrode making it fire more readily and they are very durable. I run them in both AMG Mercs and in the Volvo 245 so from the sublime to the ridiculous. I am about to order a set for the K Bike.
Regards,
K-BIKE

The Bosch XR5DC are for the 4 valves K engines and the X5DC are for 2 the valves.
XR5DC : R = denotes a resistor spark plug.

I cannot find anymore the X5DC (apparently Bosch stopped the production ???) and I replace them by NGK D7EA. I believe that NipponDenso X22ES-U will work on 2 valves K bikes.

Here is a chart for Bosch plugs and the meaning of letters and #

Bert

These are the model, year and gap recommendations from the Denso website http://www.densoiridium.com/find_part.php?tab=2
Regards,
K-BIKE

1988 BMW K100 1,000 cc IX24B 0.035
1991 BMW K100 K1 1,000 cc IX24 0.020
1992 BMW K100, K100RS 1,000 cc IX22B 0.035
1991 BMW K100, K100RS, K100LT 1,000 cc IX22B 0.035
1988 BMW K100LT, K100RS, K100RT 1,000 cc IX24 0.028
1989 BMW K100LT, RS 1,000 cc IX22B 0.035
1988 BMW K100LT, RS, RT 1,000 cc IX24B 0.035
1992 BMW K1100LT 1,100 cc IX22B 0.035
1997-1994 BMW K1100LT 1,100 cc IX22 0.024
1995 BMW K1100LT, K1100R, K1100 1,100 cc IX22B 0.035
1994 BMW K1100LT, K1100RS 1,100 cc IX22B 0.035
1996 BMW K1100LT, RS 1,100 cc IX22B 0.035
1997-1994 BMW K1100RS 1,100 cc IX22 0.024
2003 BMW K1200GT 4-stroke 1,171 cc IW27 0.028
2003-1999 BMW K1200LT 4-stroke 1,171 cc IW27 0.028
1998-1997 BMW K1200RS 1,200 cc IK20 0.032
2003-2000 BMW K1200RS 4-stroke 1,171 cc IW27 0.028
1994, 1992-1991 BMW K75, K75RT, K75S 750 cc IX22B 0.035

Thanks for that info and I was probably aiming towards the NGK plugs and had forgotten about the Iridium or assumed they would not have one to suit but the Denso site is quite comprehensive in the models they support. I am also showing my age as I remember when the "U-Groove" was introduced as the greatest thing since sliced bread. I also notice that NGK has an Iridium plug and found another site recommending a double Iridium plug. So plenty of food for thought.

Regards,

Phil

Please.....
what is the other site recommending the double iridium plug ?

Thanks

Bert

Hi Bert the website is : http://purchasenet.com.au/shopping/double-iridium-sparks-plugs-p-30.html and once again sound like the greatest. The catalogue only specified cars although just about every make and model, and from memory there are some parts on the K series engine similar to the early 3 series car so their may be one suitable.

Regards,

Phil

Hello to everyone,

Last week i have changed the spark plugs of K100RS!

After talk with some friends and my mechanic i choose the NGK Iridium DR7EIX.

I have already make some kms, and i like them. I also note a little decrease in fuel consumption!

Have anyone also test it?

Good curves

yes the ngk iridiums work well ... have been useing the platinum versions of them for years and lately have tried the iridium versions since i changed the coil for a higher energy output and slightly bigger gap.. (not bmw application )...(nice result by the way). they are on my list of must haves ....as soon as i get rich and other issues have been resolved on the k.

I'm trying to sort out a minor but irritating problem which has made me look up advice on plugs.
Since it went back on the road it has been slightly harder to start, tickover is lumpy and its a bit of a pig in traffic.
Checked coil connections and looked for sparks or clicking noises at the plugs. All okay.
Started to wonder about the new Bosch plugs I installed.
Correct grade but read recently about someone else who had similar problems with a new set of Bosch plugs.
Bert had said that they were out of production but these were made in Brazil. No offence to any Brazilians reading this but I assumed Bosch plugs would have been made in Germany.
Going to try a set of NGK's to see if it helps.
Wasn't doing this before and have shimmed valves, synchronized injectors, new air & fuel filters and new fuel pump.
Performance is fine above 1000-1200 rpm otherwise.

Perso :arrow: NGK DR8ES L

john ....lots of plugs these days come without the ferule ...leaving only the threaded section at the top of the plug ..

the plug tops are set up for the ferule to be there .

i trust this is the case with your bike as i found that my old plugs had been installed without them . since replacing mine ( merry chase to find ferules ) the bike starts and runs like a dream .

Hi there, Ive been using champion RA8HC for the last 14000km with no problems and excelent results.
Best regards
JAP

Hi Charlie. If only it had been that simple.
The Bosch plugs came with them attached.

Thanks JAP. Rarely see Champions here now.

Comberjohn wrote:Hi Charlie. If only it had been that simple.
The Bosch plugs came with them attached.

oh well ! there have been some excelent sugestions for options here john , hope you get your "pig" back to normal soon huh ?

my car runs woefully on the "standard" lowgrade fuel we get out here, is verry poor performance up to about 2.5k . so i use the highest grade whenever i can , have you tried the shell high grade john ?

Fuel is bad enough at $10 a gallon here.
Still think its a bad plug. Won't know for sure until I swap them.

I am using NGK D8EA with good results. I've left them in there for at least 30,000 kms and in Australia's 'generally' warmer climate this slightly 'colder' sparkie has no ill effect on the engine's performance or fuel mileage. A bike mechanic in Perth WA once told me in no uncertain terms that the cross reference from Bosch X5DC to NGK had to be NGK's '8' range and not the '7' that some use. I have not verified that information. Someone's pinched my NGK book!

(Update) Everything I read online suggests the '7' range is suitable for 8V and 16V K100 models, as you know. I want to add that the '8' range last a very long time for me in my bike, in the Aussie heat, don't load up and the bike performs as well as when I once used the D7EA. I did notice a slightly better fuel mileage figure overall with the D8EA plugs, but this can be influenced by a whole host of other conditions. I will stay with the '8' for now.

I'm using the D7EA with good results.
Have a look what you need/want; the 'R' stands for resistor. The first bikes had resistors in the cap and lines so can do with a D7 (or D8 if you like). Newer bikes will need a DR7 as those leads/caps are fitted without resistors.

Yes, this is true, the 'R' is for resistor. I am not using OEM ignition leads any longer, but instead have a way-cool (blue in colour, Blakey!) custom set fitted without the 5K ohm caps. They work a charm.

Two Wheels Better wrote:Yes, this is true, the 'R' is for resistor. I am not using OEM ignition leads any longer, but instead have a way-cool (blue in colour, Blakey!) custom set fitted without the 5K ohm caps. They work a charm.

TWB, are these leads a specific K set or made up, a lot of folk trade up to silicone leads as its said they last longer and do not break down with age as copper core ones, not yet tried them my self so cannot comment.

BIG D

Big D, I went to the local parts shop and bought some 8mm silicone leads in the correct lengths (as equal in length as I could get but still have room for them all to fit) with a 90 degree elbow at the spark plug end. They're slick, cheap, fall into the 'correct' resistance range, and readily available. I have to say that although my OEM leads each registered as fair to ok according to my ohm metre the replacement leads show a marked improvement in smoothness and rev-ability. I'm happy, and it cost me less than $30 skins.

Thanks TWB, thats the info I was looking for I will give them a bash when I change plugs soon.

BIG D

TWB
Did you use the original metal caps or aftermarket ones?
Having seen some of the prices for some K leads, ( ouch! are they gold cored??)
I reckon I'll be nipping down the local automart for mine too
when I need em

Would someone clarify, is it ok to use resistor plugs,DCPR8E, with resistor plug leads. Could this cause erratic starting and idle? John

k100virgin wrote:Would someone clarify, is it ok to use resistor plugs,DCPR8E, with resistor plug leads. Could this cause erratic starting and idle? John

When I used NGK resistor sparkies with 5K ohm resistor caps I noticed a sluggishness or lack of crispness to the engine when revving, indicative of a weaker spark. Replacing the plugs with the correct non-resistor variety put a stop to it straight away. Charlie99 was with me at the shop the day I discovered my mistake. He might have a learned opinion on it too.

"TWB
Did you use the original metal caps or aftermarket ones?
Having seen some of the prices for some K leads, ( ouch! are they gold cored??)
I reckon I'll be nipping down the local automart for mine too
when I need em"

I've just noticed this, a bit late I know...I am using NGK 5K ohm resisted end caps with those silicone leads.

By using a resistive cap or plug in conjunction with resistive leads you create a mismatch in impedence in the circuit and then most of the power generated by the coil is disipated in the coil as heat and not at the gap of the plug as a big fat blue spark.  this is quite detrimental to the coil as it overheats and to the plug because it doesn't get hot enough to remain clean.

My /2 came with the DR7EA plugs.

Swapped for D7EA and the revs at idle dropped about 300rpm.

Charlie suggested a reason, but in one ear..

Thanks for info. The reason I asked was I have taken the K100 on as a project because it has issues, one of them being poor starting. The plugs, which are an odd choice, are new and fitted by the previous owner I'm guessing, to try and eliminate the fault. I have no way of knowing as I bought the bike from a breakers who, quite rightly, thought it too good to break. Will change them for the correct ones today and go from there. John

Ran NGK D8EA(s) on my 2-valve bike back in 2012. Last year I went with the standard Bosch plug and fuel mileage went down (but I did pick up a nice set of bobbins). This year I'm trying out the D7EA.  

In Australia's climate I can get away with NGK D8EA, but just for fun I use the projected tip DP8EA which places the 'lectrode that tiny bit further into the combustion chamber without smacking the piston top. Does it do anything tangible? Eff if I can feel it. But I got a good deal on them because they fit a range of Japanesey things, hence, they were more readily available when I was looking. DP7EA are available too, for those who want a 'hotter' plug - NGK, the number goes down for hotter, Bosch, the number goes up.

Thanks for posting this mate!  I'm going to give the DP7EA a shot as I can get them at a very good price thru my Amsoil dealer and the old girl needs some new ones... did you notice any bump in mileage?


OG

For what its worth I have used NGK D8EA, no problems but they don't come with the screw on fitting for the caps so one must be careful to retain these when changing plugs.

Last set of plugs I removed, Bosch I think, had the tops moulded on. Can't be unscrewed and the new ones came without the tops.
Scrounged a set from a lawn mower repair shop.

I will never recommend using projected electrode plugs when it's not the recommended plug.
When I worked for Honda Australia we would see many of the smaller biker (up to 500cc) with holes burnt in the pistons because they used projected electrode plugs. Warranty was always denied if the wrong plugs were found in the engine.

The combustion chamber temps get quite a bit hotter and detonation can occur as well as the holes in pistons trick.  There is no reason the small bikes were prone to it other than they were more likely to get riden hard than the bigger bikes were but the 900cc and 750 4 cylinder twin cam engines were also prone to it if riden hard.  If any bike came in with holes in pistons that was generally the reason.

Air cooled engines are more likely to suffer but only because the water cooling will get that extra heat out quicker but that said it is not a real good idea to run the projected electrode plug unless it is the recommended plug.

Stuck with no material to compare, I have 3 K75 bikes.
How to check (with a meter, have a good one) if I have the resistor cables/caps or not?
All have the original cables.

And, would like to place irridium plugs, driving mostly between 5000 and 9000 rpm, wich would be the best?

"And, would like to place irridium plugs, driving mostly between 5000 and 9000 rpm, wich would be the best?"

Before you waste your money buy a set of standard plugs and see how well new ones perform.
You only need a spark to ignite a petrol/air mix, and a spark is dependant on the volts making it.
Try an experiment if you don't believe me: Fill two small cups with petrol, strike a regular match and throw it into the first cup - it goes bang. Now try getting a nice expensive match with some gold plating and do the same with the second cup - it still goes bang.

Wheeldigger wrote:Stuck with no material to compare, I have 3 K75 bikes.
How to check (with a meter, have a good one) if I have the resistor cables/caps or not?
All have the original cables.

And, would like to place irridium plugs, driving mostly between 5000 and 9000 rpm, wich would be the best?

Stock K75 plug leads have a resistive gap in them.  Due to the gap, they will not show any resistance on an ohmmeter. (Nor continuity.)

K100 leads do show resistance.

Duck; Thanks

Bikerboy; a Hero-Honda 125cc brings me everywhere too, but then I wouldn't be at this forum.
Had a Goldwing 1200, went from original to irridium, runs better.
Same with my Jawa 640, starts better, runs better and a bit less fuelconsumption.

Every K I had, had original Bosch plugs, now I know my daily K, would like to switch.
I have and can spend money on my K, don't try to look in my wallet.
I put my question here that I don't have to buy 4 brands plugs, don't have to invent the wheel again.

I have found the NGK D7EA plugs to be as good as any and better than many.
There are some engines that will work better on a particular brand of plug but I have never found an engine that didn't work well on NGKs

As the ad in the early '80s said, "NGK, the original copper core spark plug, since 1959."

Great topic.

I have gone with the flow and just come home from the local auto parts shop with my shiny new NKG D7EA plugs. The plugs I removed were Bosch. I am no mechanic (obviously) is the resistance cap the bit that screws on the lead end of the plug? The new plugs don't have this nipple thing and I am a little worried that they will not fit the leads tight enough. Any advice?

You need to have that nipple on the NGK plugs or the OEM plug caps wont fit correctly and will arc inside and burn out.
The you end up with a great heap of white powder up unside the cap and it doesn't work very well.

Thanks Rick.

Will have to see if any service centres are chucking some out as they cannot be purchased separately.

ask for some at any service centre .......they used to be supplied as standard but that has changed over the last few years ....you need em !!!!
once got ...just transfer them across to the replacements as time rolls along
the oem leads have the resistance built into the leads ...so there is no resistor type plug top ...unless you have copper cables installed

worth while checking the resistance of the lead in any case ...we have seen some dreadfull results ...surely affecting performance big time

so from plug top (use a paper clip to get in there ) set the meter to 20,000 ohms )) to coil end  
number 1 should be about 5-6 k  ( k = thousand ohms )
2  3 and 4 should be about 5k

if you find much variation from this ...firstly clean up all the terminals  then measure them again

if they are off the scale....  get some new cables (maybe just the ones affected to start with as a stop gap measure

just a heads up big

edit ..opps bit late

Thanks. I am pretty sure there are oem leads installed but I will check.

Charlie, I had my electrician mate come and check the leads with his meter and all were within tolerances. 
I also got some plug nipples and the bike is running better than ever!

great result mate !!!

Sorry to resurrect an old topic but I can't find a definitive answer to this question anywhere. The handbook recommends a Bosch XR5DC plug for my K100RS 16v, or the NGK equivalent DR7EA, i.e. a resistive plug. But... the leads are clearly marked as being 5k ohm resistive, so it appears that the resistance is being duplicated with this combination. It is possible I suppose that the leads are not the originals, which may have been replaced with the earlier 8v type. So which plugs should I be using with the resistive leads? Thank you in advance for your help.

Edited to add that NGK's partfinder website recommends D7EA non-resistive plug for the 16v!

If you go to realoem.com and enter the last 7 digits of you vin# you'll be able to search parts for your model.
Resistor plugs XR5DC are specified
NKG also specify resistor plugs DR7EA
Looks like you were right but if you want to keep the resistor HT leads you have, just use non-resistor plugs like D7EA