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Setting Onan points


Has anyone ever set the points on their Onan with a dwell meter ? Feeler gauges are okay but a...

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Old 03-14-2012, 11:00 PM
lokay5 lokay5 is offline
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Default Setting Onan points

Has anyone ever set the points on their Onan with a dwell meter ? Feeler gauges are okay but a dwell meter is much more accurate a necessity because the points determine ignition timing.
If so, does anyone know off-hand what dwell should be on a BF or a BFA?
Thanks!
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Old 03-15-2012, 10:29 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Setting Onan points

Onan never published that information.
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Old 03-15-2012, 01:04 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Setting Onan points

Set the poinrs so that you just have a sllight drag on the guage. Then hook up your dwell meter, and write down the reading you get. How mwny cylinders does the engine have? What is the point gap supposed to be set at? If you get a variation in the reading, as the engine is running, then the bearings in the distrubuter are bad, causing erratic timing.
Andrew
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Old 03-15-2012, 02:18 PM
Magnetite Magnetite is offline
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Default Re: Setting Onan points

AKAIK, the BF/BFA models don't have a distributor - they use the wasted spark design

Dwell is a measure of the percentage of time during each rotation that the points are closed. You can convert that percentage directly into the dwell angle since it's a percentage of 360 degrees. That's a measure of how long the coil has voltage applied to it to store energy in its magnetic field and that affects the spark strength. However, dwell angle doesn't really tell you if the timing is correct. Technically, it also tells you nothing directly about gap size, although for a given known lobe shape one can figure out the gap size - and hopefully the lobe shape doesn't change much.

To determine the timing you need to know when the points open, not how long they are closed, and you get that only from the timing light. If the point gap is set reasonably close, there will be plenty of time for the coil to charge and you can then set timing with a light to get correct operation.

Of course, many of us are lazy and know that if the procedure above was done at the factory, the points box will be set to give the correct timing when the gap is correct. We can skip the timing light step by consistently setting the same gap every time. I'm having trouble reading the 19 degree BTC mark on my CCK, but I can reproduce the same timing by simply getting the point gap correct. I could use dwell to indirectly measure that gap and make the same assumption that things haven't changed since the last time timing was set correctly, but if I'm going to drag out the dwell meter, I might as well drag out the timing light and directly measure timing. It's going to be more accurate than setting timing by dwell angle.
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Old 03-15-2012, 06:40 PM
Dave Edmonds Dave Edmonds is offline
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Smile Re: Setting Onan points

My experience with points setting has been that, if the gap is not set very close to where it's supposed to be, the points will either not break, or will not make. Apparently, there is not a lot of "lift" on the lobe that operates the points; if you don't get it VERY close to right, the critter won't have any spark because the points are either not opening, or not closing. I always double-check with a test light across the points after changing and setting them to make sure they're doing what they're supposed to be doing.
Dave Edmonds
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Old 03-15-2012, 08:28 PM
Lloyd H Lloyd H is offline
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Default Re: Setting Onan points

Buy a set of Snap-on feeler guages # FB316B $6.65 made just for setting points. 1/4" by 1 3/4" blades, you'll love them with the first use.
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