ok, the service manual for my bike says the gap on the plugs should be .038-.043, and the service manual for the S&S super b carb says it should be
.022-.025. which one do I go by?

 

Gap has some to do with the type of plug, but mostly it has to do with the
type of ignition.

Around 0.40 sounds about right for an electronic ignition.

Points are a little tighter but not much, maybe around 0.35 to 0.38 - I don't
have a bike with points though so don't trust my numbers!!

And a magneto has the tightest gap at approx. 0.20.

The carb type has no relevance to the plug gap... so I'd trust your service
manual, if you have a stock ignition setup, or go find the ignition manual if
you have after market. And 0.22 to 0.25 doesn't sound right for anything.
AFAIK

Gazza

 

go with .040 personally i'd go with the service manual


check out the ironhead section over on xlforums as well, lots of good info between these two sites http://xlforum.net/vbportal/forums/forumdisplay.php?f=7



http://www.nightrider.com/biketech/hdsparkplugs01.htm

http://www.mrgasket.com/pdf/Sparkplugs.pdf

 

thanks guys