I replaced the battery with the proper size YTZ7S Yuasa and ran some tests to check the rectifier/regulator and the charging system (magneto).
First check was the "charging voltage". I got a reading of 14.6 volts with the engine running. Perfect.
Next check was for the "charging coil resistance" on the DC side. First thing I don't understand: The shop manual says to set the tester to "ohm x 1". There's no setting of that description on the tester. I set it to 200ohm setting. With the engine off, the reading was 0.7. Target reading is 0.2245 - 0.336 ohm. I'm not sure what I've got.
Third check was for the output of the rectifier/regulator (AC lighting circuit). Setting on tester should be ACV-20. Lowest setting on my tester is ACV-200. On that setting, my reading was 12.2V at 1/4 throttle and 13.0V at idle. Target is 13.0 - 14.0 V at 5000 rpm. Regulator bad?
Another strange thing - I swear my headlight use to come on as soon as I turned the main switch on. Now with the new battery, it only comes on when the engine starts running.
Edited by Navaho6, January 28, 2010 - 08:49 PM.