dfill

I've got a Yamaha DT 400 enduro which has served me well since 1978. I went to start it the other day and no spark. plug is good and no current exiting the spark plug cap/boot. Of the three coils under behind the flywheel, which must be working for the bike to fire? (i have no lights and no battery so one or two of these coils may not be necessary) Does anyone know the correct resistance/ohm readings that should correspond with each coil(including the ignition coil under the gas tank)to tell which coil is and isnt working. I figure once I get the coils right I'll know whether the cdi unit needs replacing. thanks in advance for any input anyone may have