Magneto Timing?

Sat Aug 07, 2004 11:01 pm

A few post back I posted some questions, About mag timing, John *.-!.* said to adjust timing to top dead center using an timing light. Which I tried doing so I could only get half way between the before top dead ceter mark (bftdc) & the top dead center mark (tdc) before I ran out of adjustment at the bottom of the mag where it bolts to the engine. what do I need to do so I can time for top dead center? cub is still hard to start with an cold engine. Thanks Dave F.

Sun Aug 08, 2004 8:30 am

Actually the BTDC is for use with light with engine running, the TDC can be adjusted by just listening to the click. To time, loosen the clamps and turn the magneto so top is closest to engine. Set pulley to TDC (2nd mark), and turn mag until the impulse just clicks. If you can't get it to click at the right point, there is a good possibility that someone in the past has not gotten the governor gear timed right when reinstalling. When I bought Missy the mag had been replaced by a distributor, because of the same problem, and the shop sold the owner a distributor rather than correcting their screwup.

Sun Aug 08, 2004 8:51 am


It sounds like your mag is WAY too far advanced... enough so to give you trouble with kick-back. It may be that the governor gear isn't timed correctly, otherwise John's advice should put you spot on.

To double check if your timing is correct when you finish, crank VERY slowly until the impulse clicks. If it was to fire #1 or #4, the pointer should be exactly on the second mark. If it was for #2 or #3, the pointer will be exactly opposite the mark.

If the impulse is working correctly, there is no need to use a timing light.

We'll be heading to Portland, IN in just two weeks. See you and Brenda there.

Sun Aug 08, 2004 9:48 am

George Willer wrote:If the impulse is working correctly, there is no need to use a timing light.

The only use I have seen for a timing light is to verify that the impulse coupler produces the right advance at higher speed after it disengages. At full engine speed the timing should approach the advance notch. It won't reach it because the notch is at 16 degrees to match the battery ignition spec whereas the mag only advances to 13 degrees.