ignition timing

[RICHARD A. WHITE]

All that work … and still no promise of the 2 cylinders firing 180 degrees apart, high point on the cam is subjective at best, Frank, do you still have the photos showing just how many degrees the “high point” is on some cams? My point being the timing tool sets the points to fire right when they need to fire, not 3 degrees early, not 2 degrees late. As most of you know 2 degrees will make a difference, then add them not firing180 apart, just compounds the situation… Can you get it right with feeler gages? Most certainly, but not every time, with the proper tool it is almost guaranteed.

To each his own I guess

Regards
Richard

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[frankr]

The high point on the cam means nothing when using the timing fixture. The high point is only important when setting them by gap (0.020″). The timing fixture sets them by WHEN they open not how far they open. WHEN s the most important, not how far. “How far” only approximates the “when” time. Richard, being a toolmaker can probably explain it better than I can, since he daily works with angles and sines & cosines and all that good stuff.

[wrenchero]

hate to throw a WRENCH in all of this but if the points are both set to .020 then wouldnt they have about the same dwell.by changing the point gap to get them to open at the right time ,you change the dwell i think? unless its a very small amount i guess?

mn

[crosbyman]

step #7 is for emergencies

the tool… is better

Joining AOMCI has priviledges 🙂

[fleetwin]

wrenchero wrote:

hate to throw a WRENCH in all of this but if the points are both set to .020 then wouldnt they have about the same dwell.by changing the point gap to get them to open at the right time ,you change the dwell i think? unless its a very small amount i guess?

They might have the same dwell, but that does not ensure the timing is even/right. on both cylinders….The dwell certainly plays a part in the timing on one of these engines, but it is not the only consideration…Think of an old chevy V8 with conventional ignition….First you set the dwell, then set the timing with the engine running….But, if you readjusted the dwell after setting the timing, the timing would be slightly different…
On this outboard, there are two notches on the flywheel…Anywhere in between the two notches is “OK”….But, I’m betting your timing will show up between the two notches if you set the gap to .020”. Needless to say, using the timing fixture is more exact…But, the small stack up of tolerances will probably end up showing a slightly different result statically vs. running with the timing light…
But, again, I just don’t want you to get mired down in the fine details here and get even more confused. By all means, set the timing/dwell with the fixture and ohmmeter if you feel confident in the procedure after watching it online and reading the posts. But again, there is a “timing fixture” that is prescribed/supposed to be used instead of the flywheel for this procedure. But, after thinking about it a bit, using the flywheel may actually be a more precise way of doing this job…But, it is much easier with the “timing fixture”….

[frankr]

wrenchero wrote:

hate to throw a WRENCH in all of this but if the points are both set to .020 then wouldnt they have about the same dwell.by changing the point gap to get them to open at the right time ,you change the dwell i think? unless its a very small amount i guess?

What has the dwell got to do with it anyway? This is a magneto, not a car.

Anyhoo, one last time, as the flywheel magnets pass by the coil’s laminated core, a voltage is generated in the coil. At a certain point in the magnets passing, the voltage polarity in the coil is reversed. It is at that TIME of reversal that the points just barely break as they first touch the ramp on the cam. That is what the timing fixture does—-ensure that the points break at the TIME that the voltage reversal occurs. If the points break at the correct TIME, you will get maximum efficiency and best spark. Once the points make that break it is all over till the next time. I don’t care if they open 20 thou or a half inch, as long as they open at the right TIME. Dwell has nothing to do with it, as long as they close again by the time the magnets come by again. Yes it will have spark and run if the TIME is a bit early or late, Heck, I’ve set the gap by eyeball measurement and gotten spark. The question is, do you want the best or will you be satisfied with “OK”.

Now, go ahead and do it however you want.

[The Boat House]

• This reply was modified 4 years, 1 month ago by The Boat House.

[squierka39]

Well explained Tubs. And to add to the fun, if you have a pre war Johnson they went and put the timing marks on the mag plate and flywheel for us, no extra fixture needed. I suspect they omitted them in the newer motors for simplicity and the average home mechanic to just set them by feeler gauge. But they still gave the shop mechanics the tools to do it precisely.

[fleetwin]

Frank and Tubs are correct about “dwell” on these engines, not really an issue, unless the adjustment is way out of whack….Service procedures and theory never mention dwell and there is no way of really checking it either.

[wrenchero]

Ok this is great info. I am an auto mechanic and now I understand about the magneto. I asked about it because I did this similar procedure on a Tecumseh and figured I would like to try it on my outboards. Thank you all for the help

mn

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