timming mark is their spark every 360 or 720 degrees

2 replies to this topic
  • fridder

Posted October 03, 2005 - 08:55 AM


rebuilding 99 yz400f

when putting the cam chain on can you have it 360 degrees off on the lower timming chain sprocket?

does it supply spark every time the mark lines up or does it skip a revolution.

I know how the cam sprockets line up to the to the mounting surface of the valve cover and the cam loabs point out.

one revolution on the timming gear = one revolution on the piston so could I have it sparking when the piston is cumming up to exhaust?

the book does a great job of describbing most everything but haven't found anything to make me understand this problem

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  • mkporn

Posted October 03, 2005 - 09:03 AM


no and yes. No to the three 360 and I think that it is a yes to the twice spark...

  • grayracer513

Posted October 03, 2005 - 09:15 AM


The ignition is crank triggered, and fires every rotation, creating a "wasted" spark during the overlap phase at the end of the exhaust stroke. It cannot be timed on the wrong TDC, since it is the camshafts that determine which is which.

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