hi andrew , from the clymer manual , ignition coil , primary(small wire ) to ground 1.0 ohms plus or minus 10% secondary (high tension lead) to ground 59000 ohms p/m 10% , seems to be a general spec for all models , the charge coils , says no specs available pre 1980 , the 400 d is different but might give u a guide ,it 425 high speed winding red to blue 35 ohms p/m 10% , low speed winding brown to black 240 ohms p/m 10% ,pulser coil white/red to black 4 ohms p/m 10% the 400 from memory has one charge coil only and by looking at the wiring diagrams ,yours ( at a guess )would be the brown to black ,i had a look in the yz manual for an equavlent yz , it doesn,t show any values at all , just says replace if in doubt ! u,ll be able to check the pulser and see if u can get a value on the charge coil , i hope this helps
