1981 Honda cb900c is not charging at low rpms. There are two issues I've found that could be contributing factors but could use some feedback before I invest more money in parts. The first issue is the resistance on the rotor is only 2.9 ohms instead of 3.6 to 5.2 required. And the other thing is voltage is dropping a volt through the ignition switch which means that voltage to the rotor is low. No charging at low rpms and at higher rpms the voltage doesn't get much higher than 13 volts. Probably just need to replace both rotor and ignition and go from there but wouldn't mind some feedback. Thanks.