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Collection, Preservation and Display of Old Lawn Mowers

Timing Suffolk engine


I've a short question and I hope that somebody got the answer.

How can I check that the magneto is timed to spark at 22 - 24 degrees before top dead centre? Are there any timing marks available?


I want to remove the magneto with base plate in order to be able to paint the block. 

hillsider Thu, 23/02/2012


I expect that you have noticed that the flywheel and the cam lobe for the contact breakers are both keyed to the crankshaft so nothing to worry about there. If the engine was running ok before dismantling it I would mark the points plate with a small sharp chisel to create an alignment mark adjacent to the upper of the two securing bolts and covering both the plate and the threaded boss of the engine side pate. this should allow you to realign to the original position.

Alternatively you would need to prove the opening point of the points using a test light or a multi meter, the degrees before TDC could be checked using a timing disc or a protractor marked of in degrees.


Toetsje Fri, 24/02/2012

Hi, thanks for your reply.

The engine was running fine, however I think that the timing could be improved. Therefore I would like to verify the timing settings. I have little experience with these old engines but with some help it should be possible to do this.

If I understand you correctly I need to follow these steps in order to verify and change the settings.

  • Set piston at TDC using a piece of metal in the sparkplug hole.
  • Mark flywheel and backplate
  • Remove flywheel and points plate
  • Mark 20 degrees before TDC using a timing disc on the backplate
  • Connect a multimeter
  • Mount points plate and flywheel and verify settings
  • If needed, remove flywheel in order to change the settings.

This method doesn't seem very accurate to me. I.e. I can move the flywheel a few degrees without a noticeable movement of the piston at TDC.


hillsider Fri, 24/02/2012


Yes I think you are on the right track in your interpretation of my suggestion, you could also watch for  the contacts to commence opening through the viewing slot in the face of the flywheel using a very thin feeler gauge to detect  the point where the contacts start to open to avoid removing the flywheel every time.

Re accuracy I find that getting points gap and the carb mixture setting correct has far more influence on the performance of the engine than altering the timing from it's factory settings. These engines are fortunately not as demanding as modern engines re settings, they are not exactly formula one technology.