Quote:
Originally Posted by wearetwomariners
Are these both spark plugs? Does the front one just look different because theres an end missing or something?
Thanks
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Oh wow! I haven't seen one of those heads in a very, very very long time.
That second spark plug hole is actually where a compression release would go. Somebody removed the release and threaded a spark plug in.The compression release was a one way valve that thread into that hole and controlled by a cable running to a thumb lever on the handle bars.
Back in the day, a release was needed to help kick over some of the higher compression motors and also used to aid in braking. sort of like a Jake brake in semi's.
In the early 70's the Bultaco 360 ruled the short flat track scene.
The hot tip was to have the head machined with the second plug hole for a compression release. This helped the bikes slow down enough at the end of the straights in order to get into the turns