Discussion on point gaps and timing

Posted by David G on September 27, 2015 at 11:07:53 from (63.152.64.213):

I see a lot of discussion on point gaps and timing, so here are my assumptions:

Point gap on a magneto must be set so the points open when the magnetic field is strongest, so it is critical.

Point gap on a distributor based system is the best of both worlds for being able to open/close correctly through all the RPM ranges. It seems like .020 is the industry standard. Initial timing should not change between subsequent times points are being installed, and should be considered a double check that all is correct. If you set the point gap consistently initial timing should be exactly the same each time when new points are installed. Timing should ALWAYS be done after points are installed or cleaned up. If timing is different, something is worn or set wrong.

If point gap is too close, timing will be retarded, if too loose, then it will be advanced. I use this on small engines with battery powered coils to adjust the timing a little of I want to.

Initial timing should be advanced enough to allow for the spark to occur at the right time when full RPM, but not kick back on starting, period. The distributor has a mechanical advance in it to move the timing from the initial value to full advance. It does the best it can with only being able to look at one variable which is RPM. A computer can control timing much better, because it can set initial timing at 0, it can look at RPM, load and temperatures to determine advance.

The manuals for the tractors which were built in the 40s-50s assumed the tractors would be hand started and fuel was low octane. The optimum timing can be achieved by ear, and is usually a couple of degrees more advanced than the books have it. I run at full throttle, then adjust timing to max RPM. I then check it with a light as a double check. You will want to back the timing off a little if it kicks back when starting hot, if you work it really hard to prevent pinging, or if there is a flutter at idle due to timing too advanced there.

Timing too advanced does NOT cause run on, it is 90% caused by idle set too high.

If timing bounces, then you have an issue with advance mechanism, worn gears or worn bushing, probably worn bushing.

Please post your comments, always great to have good discussion.

Replies:

• Re: Discussion on point gaps and timing Rusty6 07:36:54 09/28/15 (0)
• Re: Discussion on point gaps and timing M-MAN 20:05:12 09/27/15 (0)
• Re: Discussion on point gaps and timing David G 18:27:29 09/27/15 (0)
• Re: Discussion on point gaps and timing jimg.allentown 18:02:58 09/27/15 (1)
  • Re: Discussion on point gaps and timing David G 18:25:28 09/27/15 (0)
• Re: Discussion on point gaps and timing TomH in PA 17:29:00 09/27/15 (0)
• Re: Discussion on point gaps and timing Dave in Tx 15:54:59 09/27/15 (5)
  • Re: Discussion on point gaps and timing Janicholson 16:55:28 09/27/15 (4)
    • Re: Discussion on point gaps and timing David G 18:37:09 09/27/15 (0)
    • Re: Discussion on point gaps and timing Dave in Tx 17:20:00 09/27/15 (2)
      • Re: Discussion on point gaps and timing RandyB(MI) 18:35:22 09/27/15 (0)
      • Re: Discussion on point gaps and timing teddy52food 18:26:46 09/27/15 (0)
• Re: Discussion on point gaps and timing robgIN 15:01:20 09/27/15 (3)
  • Re: Discussion on point gaps and timing David G 18:40:25 09/27/15 (0)
  • Re: Discussion on point gaps and timing jimg.allentown 17:48:03 09/27/15 (1)
    • Re: Discussion on point gaps and timing robgIN 19:37:42 09/27/15 (0)
• Re: Discussion on point gaps and timing notjustair 13:30:33 09/27/15 (1)
  • Re: Discussion on point gaps and timing todd hamilton 18:18:05 09/27/15 (0)
• Re: Discussion on point gaps and timing todd hamilton 12:26:07 09/27/15 (0)
• Re: Discussion on point gaps and timing Joe Mindy 11:53:30 09/27/15 (0)
• Re: Discussion on point gaps and timing guido 11:47:24 09/27/15 (0)
• Re: Discussion on point gaps and timing Dean 11:15:53 09/27/15 (5)
  • Re: Discussion on point gaps and timing Janicholson 12:02:16 09/27/15 (1)
    • Re: Discussion on point gaps and timing Dean 19:28:44 09/27/15 (0)
  • Re: Discussion on point gaps and timing David G 11:20:33 09/27/15 (2)
    • Re: Discussion on point gaps and timing teddy52food 18:37:32 09/27/15 (0)
    • Re: Discussion on point gaps and timing RandyB(MI) 18:26:09 09/27/15 (0)

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