Spark plug gap - BMW Luxury Touring Community
 
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post #1 of 4 Old Jan 29th, 2017, 3:34 pm Thread Starter
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Spark plug gap

Seems I remember reading that adjusting the gap on new plugs is not necessary. I bought a new set of Bosch XR7LDC plugs. The gap on them is about .019 inch. The owner's manual says no adjustment is necessary, but Clymers gives a gap range of .0315 inch plus or minus .0004 inch. Should I adjust the gaps or leave them alone?

Thanks
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post #2 of 4 Old Jan 29th, 2017, 3:57 pm
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Re: Spark plug gap

The XR7LDC is a dual electrode plug and is factory gaped. If you are using a standard flat feeler gauge you will be getting an incorrect measurement as the plug uses formed curved electrodes on the sides of the anode rather than the typical flat type over the end. This curvature gap can only be measured with a wire gauge. A flat gauge can not measure the gap as it is not a flat surface between the electrode and anode.

Unless the boxes holding the plugs were severely damaged, just put them in.

Gordon
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2001 K1200LTI Champagne (current ride) Lazy Susan
1998 R1100RT Never should have sold it
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post #3 of 4 Old Jan 29th, 2017, 4:51 pm
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Re: Spark plug gap

Quote:
Originally Posted by kend52 View Post
Seems I remember reading that adjusting the gap on new plugs is not necessary. I bought a new set of Bosch XR7LDC plugs. The gap on them is about .019 inch. The owner's manual says no adjustment is necessary, but Clymers gives a gap range of .0315 inch plus or minus .0004 inch. Should I adjust the gaps or leave them alone?

Thanks
These are double electrodes plugs that need a set of wire-shape feeler gauges - normally not needed to regap/adjust, but useful tool if you have these to check. A bit tricky and delicate job to regap these XR7LDC.

You will have to be more specific on HOW you did in fact measure your 0.019 inch. A flat feeler gauge is not very precise to do such plugs.

Always possible 1 or 2 (out of 4) have been dropped or damaged in some way, but I doubt very much all 4 would come "new in-the-box" with such gap. This would be 30% below normal gap ??!! These are not used in many vehicle worldwide and were almost made custom for BMW for this K1200 engine.


ANOTHER POSSIBLE SCENARIO for your smaller gap:
-------------------------------------------------------------
When the K1100RS/LT came out (1992-1993), it was specified to use spark-plug XR5DC (BOSH) with a normal gap of 0.02362 inch gap (0.6 mm) and the wear limit was 0.0354 inch (0.9 mm), Many years later, the official BMW part catalog was updated to suggest using XR7LC for these K1100 as they cut down on producing the XR5DC (like K100 spark-plugs but with with resistor built-in).

So... assuming your spark-plugs were built for the K1100 market in mind, you would not be very far from the specific "new" gap of 0.02362 inch - in this case about 20% error... some of which could be from your measurement method.

-------------------------------------------------
John (Montreal, CANADA)
K1200RS (2002 IceBlue/Red - 96,000 miles)
-------------------------------------------------
Think twice before you hit [SUBMIT REPLY] - famous quote by another member:
"The value of this board is not founded on dismissing the ideas of others, but by posting to share our experiences and what we've learned from them."

Last edited by sailor; Jan 29th, 2017 at 5:18 pm.
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post #4 of 4 Old Jan 29th, 2017, 9:05 pm Thread Starter
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Re: Spark plug gap

Quote:
Originally Posted by sailor View Post
These are double electrodes plugs that need a set of wire-shape feeler gauges - normally not needed to regap/adjust, but useful tool if you have these to check. A bit tricky and delicate job to regap these XR7LDC.

You will have to be more specific on HOW you did in fact measure your 0.019 inch. A flat feeler gauge is not very precise to do such plugs.

Always possible 1 or 2 (out of 4) have been dropped or damaged in some way, but I doubt very much all 4 would come "new in-the-box" with such gap. This would be 30% below normal gap ??!! These are not used in many vehicle worldwide and were almost made custom for BMW for this K1200 engine.


ANOTHER POSSIBLE SCENARIO for your smaller gap:
-------------------------------------------------------------
When the K1100RS/LT came out (1992-1993), it was specified to use spark-plug XR5DC (BOSH) with a normal gap of 0.02362 inch gap (0.6 mm) and the wear limit was 0.0354 inch (0.9 mm), Many years later, the official BMW part catalog was updated to suggest using XR7LC for these K1100 as they cut down on producing the XR5DC (like K100 spark-plugs but with with resistor built-in).

So... assuming your spark-plugs were built for the K1100 market in mind, you would not be very far from the specific "new" gap of 0.02362 inch - in this case about 20% error... some of which could be from your measurement method.
Thanks to both Gordon and Sailor. I didn't notice the curvature when I first measured. This caused my measurement error. Went back with a .03 inch wire gauge, which fit nicely. Will install the plugs as they came out of the box.
Ken
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