Spark Plug Gap used....
Spark Plug Gap used....
I've read my book and it stats .38-.43 for the gaps on my plugs. When I changed them out recently I put them at .43. But I was wondering what is better, the low side or high side? Or do you just go out of the range all together?
Grand HDF Member
Joined: Jan 2012
Posts: 4,445
Likes: 2,822
From: Oklahoma
The side electrode and the tip slowly erode under use. Setting at the narrow limit allows for some wear before they go out of spec. A wide gap on a new plug is not a problem but as they wear, more current is needed to make a spark. During start, the available juice is divided between cranking and making a spark. This can make starting more difficult when the plugs are worn and started life with the gap at the max limit.
On the other side of the argument is the recommended change interval. If plugs are changed when the manual suggests, there won't be measurable wear anyway.
There is only so much electricity to make a spark. Whether you have a relatively long, skinny spark or a shorter, fat spark, the results seem to be about the same. If you ride through the winter, you may find starting is more reliable with the gap at the smaller tolerance.
On the other side of the argument is the recommended change interval. If plugs are changed when the manual suggests, there won't be measurable wear anyway.
There is only so much electricity to make a spark. Whether you have a relatively long, skinny spark or a shorter, fat spark, the results seem to be about the same. If you ride through the winter, you may find starting is more reliable with the gap at the smaller tolerance.
There is a "theory" that the largest gap possible is better, providing your coil is in good condition, because it allows a large flame kernel to develop which improves combustion. Some say to set a smaller gap w/ higher compression & so forth.
Mines at .040 & works fine
Mines at .040 & works fine
Road Warrior
Joined: Mar 2011
Posts: 1,503
Likes: 94
From: SE Michigan
+1 on the service change interval. The last set of plugs I changed in my softail were prefect. Very little wear, perfect color, I felt like I was wasting money. They were set at .40 and just plain plugs.
Last edited by Larry64; Nov 27, 2012 at 07:26 PM.
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