QuestionIhave a 1974 honda 750four that has been sitting in a barn for about 10 years. Where da I start if I have no spark?
AnswerGarry, I'll assume that you have installed a new battery in it and a fresh set of plugs.
Spark is controlled by
a. Battery power to the ignition coils, through the KILL switch.
b. Coils are switched on and off by the ignition points, underneath the point cover on the right side of the crankshaft.
c. Points contact faces must be clean and shiny, with the gaps set to about .014-.016" at the highest portion of the point cam.
d. Coils fire through the spark plug caps, which generally have about 5k ohm resistance, measured off of the coil wire end.
e. If the spark is intermittent and ignition points are arcing heavily, then the condensers are bad.
You can use an inexpensive 12v test light to check power at the coils (black/white wire) and then watch the ignition points switch on and off on each contact set. Points need to be set to open at the F mark for 1-4 and 2-3 on the point cam, as you look through the little inspection hole in the points plate.
Make sure the KILL switch has continuity through the contacts inside. When things sit for years and years, the electrical connections and contacts can all form corrosion that is a barrier to electron flow.
Bill Silver
