Coil tester/ timing light

Discussion in 'Electrical' started by Al.Fisherman, Sep 28, 2010.

  1. Al.Fisherman

    Al.Fisherman Active Member

    What I'm looking for is some feedback as far as interest. I've come up with a timing light/test light for these Chinese HT engines (I'm sure it will work on all these type coils, although I haven't tested it as of yet). With the test light you can check the output of both the BLUE and WHITE wire. This will enable you to eliminate a good coil as a potential problem when diagnosing a electrical failure. Also you can tell if the key is broken without magnet removal. As of now I have no way to test a CDI. To use this test light the spark plug is removed (eliminate compression) and the ground (BLACK) wire needs to be removed (one screw) from the coil. I'm working on a video to demonstrate.

    What do you say ........?????

  2. tjs323626

    tjs323626 Member

    I for one would like to see what you have come up with. The electrical system on these engines is a problem area. When in doubt, I check with a nail or screw inserted into the plug cap and get a jolt (harmless) if all is well. I know that some of us don't enjoy the shock and would like to have a dependable tester. The cheepo type spark testers fail all too soon and can lead one to think the system has failed when in fact the tester has failed. I sometimes use a small multimeter to test parts with. What have you come up with?
  3. Al.Fisherman

    Al.Fisherman Active Member

    When you do that you are checking the complete system. Coil/CDI/Plug Wire. I came up with a test light that hooks JUST to the coil wires. If the coil is putting out the light will light up. When the magnet is rotated it will light up showing that the magnet is approaching top dead center. I'll get some photos posted later today.
  4. Pablo

    Pablo Motored Bikes Sponsor

    A good diagnostic tool would be hugely great in the extreme. We get calls all the time from people who have never purchased item one from SBP, and they are trying to get the engine to start/spark. I usually just send them to this and the other site, after I have stepped them though 4-5 minutes of the usual suspects.....

    I have a HF in-line light that goes in series with the spark plug wire.
  5. Al.Fisherman

    Al.Fisherman Active Member

    Here is the test light I came up with.......

    Last edited: Oct 1, 2010
  6. V 35

    V 35 Member

    I Think your on the right track, verifying the mag produces voltage would be a good way to isolate out misfiring problems. Auto parts stores sell a spark gap spark tester,or you can take an old, but known good, plug, set the gap wide .050 and see if it sparks.
    Test your tester on a known good engine, before considering it a troubleshooting tool.
  7. Al.Fisherman

    Al.Fisherman Active Member

    If you use a lead and spark plug, where are you hooking it up to, the CDI? If so and no spark, what is bad, the magneto or the CDI? The idea is to isolate each component...first the magneto (if it is installed correctly) then on to the CDI. A good magneto will/can fire without or with a sheared the woodruff key or if magnet is installed backwards.
    Last edited: Dec 7, 2011