Spark plug gap

[geraldlanc]

The Honda book says gap from 039 to 043, so what effect does that range have on performance?
Gerald

[Ol' Grey]

Most manufacturer's will give a 5 point gap spread to choose from that they feel is acceptable for your model's application. The wider the spark plug gap, the more power required by the coil for the spark to jump the gap, the narrower the gap, the less power required to jump the gap.

Under normal stock conditions, my own rule-of-thumb is to choose the gap right in the middle of the acceptable range.......in this case, for example, I'd probably go with .041.

If mods were done that increased the compression ratio, which also makes the compressed mixture denser, I'd go with the narrower gap of .039 as higher compression (denser compressed mixture) makes it harder for the spark to jump the gap, so one wants a narrower gap.

[Shimpy]

The Honda book says gap from 039 to 043, so what effect does that range have on performance?
Gerald

I doubt any. Everything manufactured has a tolerance. On the gap they are giving you a .oo4 tolerance (4 thousandth of an inch) because 1. it is not that critical, and 2. nobody can set gaps with feeler guages and get it down to a precision tolerance (.001 or less)
I set mine to the low limit or .039. The reason I do this is because after many miles the gap seems to open due to wear of the electrode and moves towards the high limit keeping it in tolerance.

[geraldlanc]

Shimpy, what is an "iron butt" and how do you get to be one?
Gerald

[Shimpy]

Shimpy, what is an "iron butt" and how do you get to be one?
Gerald

The Iron Butt Association is made up of riders that like long distance indurance riding. The minimum qualifying ride is 1000 miles in a day that are witnessed and verified. There are many other rides that are very grueling. Check out their web site. IBA - World's Toughest Motorcycle Riders

[Phu Cat]

​To answer the original question of whether or not gap has any effect on performance, the answer is no. The reason is, the milli micro second the spark starts to jump the gap to initialize the flame front, the spark plug is thereafter out of the picture.

PC