Motorcycle Repair: Yamaha DT-400 1975, yamaha dt 400, spark plug wire

Question
No spark. 1st year of the ele. ignition. I'm thinking the modual is bad, but not sure. Bike has been sitting for at least 15 years. Mint condition.  

Answer
Carl,
 Work backwards from the plug.  Is it working?  Test it elsewhere or switch with a known working one.  Check condition of the high tension lead (spark plug wire) to make sure the plug cap and the connection at the coil are good.  Next test the primary AND secondary resistance of the coil with a multimeter and compare the the factory specs.  Other than that, you could have a loose connection between the coil and the stator or the sator itself is bad(unlikely if use was limited like you suggest).  The only way to test the module w/o complex equip. is to swap with a known working one.

Hope this helps,
Mike