'93 K1100LT Spark Plugs

[richo2006]

Hello all,

I'm doing winter maintenance on my '93 K1100LT and I have a question about spark plugs. Last summer I bought seven Bosch X5DC spark plugs, three for my K75 and four for the K1100. Unfortunately, I now see the correct plugs for the K1100 is XR5DC. I understand the "R" means it is a resistor plugs.

My question is, can I use the X5DC plugs or should I buy XR5DC plugs?

Thanks for your help.

Regards,

Richard in Commerce MI.

[Pauls1150]

I don't know "for sure", but the MAX site shows the correct plug for a '93 K1100 to be the XR7LDC.
EuromotoElectrics says this plug is no longer available, and infers that the XR5DC (slightly hotter) is the replacement.
The BMWLT.com site shows the NGK DCPR7EIX as a replacement;
The NGK DCPR7EA9 may also be a replacement.
You may or may not need to save the nipple nuts from the older plugs.

About the "R" part of the designation - If the bike has "resistor"-type spark plug wires, one doesn't typically use resistor plugs also, they don't play well together; but if the wires are non-resistor types, then if the manufacturer installed resistor plugs, that indicates the ignition system expects to see that in the circuit.

see also:
https://forums.bmwmoa.org/showthread...his-spark-plug
https://forums.bmwmoa.org/showthread...-a-1992-k100rs

[richo2006]

Hello Paul,

Thank you for the information. Both the Owners and Factory Repair manuals list the XR5DC as the proper spark plug. The bike has factory wires, so if the bike came with resistor plugs, then I wouldn't think they are resistor wires.

I'm going to purchase DPR7EA-9 plugs for the bike.


Regards,


Richard
Commerce Township, MI

[20774]

Usually the resistor part would be in the spark plug head. You can see if you have resistor wires by using an ohmeter to measure the resistance from one end of the plug wire to the other. Don't know what resistance to expect...on mid 70s-on Airheads, the plug head had a 5K ohm resistance.

[richo2006]

Hello,

I looked at the wires last night and the heads are marked 5K ohms.


Regards

[20774]

Resistor plugs might work but there's a chance that they would misfire or the engine would run rough. No need to add extra resistance to the spark path.