Checking the Rectifier and Charging System

1 reply to this topic
  • Navaho6

Posted January 28, 2010 - 12:51 PM


Edited: Last battery I had died suddenly during a ride. It was a weak, undersized battery to start with.

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.

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  • Navaho6

Posted January 30, 2010 - 01:42 PM


Figured out that my problem was my multi-tester, not my bike. If the manual says to test with ACV-20, make sure your tester has that setting. My AC readings were 1.5V off. Resistance measurements were way off.

My friend let me use his $400 tester, and everything checked out. My problem was a cheap battery. Its time was up.


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