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the right spark plug for a 1992 k100rs


New member
i have a question regarding spark plugs for a 1992 k100rs.
the manual says i need to use bosch XR5DC spark plugs or the ngk equivalent D7EA.
i took a plug out of the bike and found bosch XR7LDC.
The XR7LDC plug is longer then the ngk D7EA measured from the start of the threads.
I put the XR7LDC back in the bike. they are what the bike came with when i bought it and haven't hit the top of the piston yet, but why the difference.
and which should i be running.
thank you.
Hi, Alex,
New, the bike came with the Bosch XR5DC spark plug. After the K1200RS came out, BMW changed the spec to the XR7LDC plug. Either will work fine. as will the NGK DR7EA. Your dealer will charge you $8 or more EACH for the Bosch plugs.

I have had a K1100LT for 11 years and my wife has had a K75 for 4 years. I use the Autolite 4163 spark plug in both bikes. I have probably used the plug for a little over 100k miles with zero problems. I change them every 12k-15k miles. I can afford to change them often because I buy them at Checker/Kragen/CSK for about $1 each.