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Onan 4GBE spark problem


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  #11  
Old 03-05-2017, 06:47:33 PM
Tony Clever Tony Clever is offline
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Default Re: Onan 4GBE spark problem

Service Manual:
http://www.twinslan.net/~n0nas/manua...0(09-1994).pdf

Parts Manual:
http://www.twinslan.net/~n0nas/manua...0(01-1998).pdf

Operators Manual:
http://www.twinslan.net/~n0nas/manua...0(07-1997).pdf

Installation Manual:
http://www.twinslan.net/~n0nas/manua...0(10-1996).pdf

Hope this helps

RE: Holy banoonies. I went to look for the manual.
Sorry, I'm lost.

Last edited by Tony Clever; 03-05-2017 at 07:00:26 PM.
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  #12  
Old 03-05-2017, 10:42:51 PM
bbqjoe bbqjoe is offline
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Default Re: Onan 4GBE spark problem

I just had a thought.
It looks like an awful lot of trouble to split the engine from the generator.

Is there any reason at all that I can't mount the ignition sensor above the cooling fan on the rear, and mount magnets to the fan so they correspond to TDC?
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  #13  
Old 03-05-2017, 10:50:47 PM
len k len k is online now
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Default Re: Onan 4GBE spark problem

Actually I was thinking of something like that for my other Onan. I think most of these emeralds have a power take off mount on end of genhead,
I was thinking of drilling the flywheel and press fitting magnets into it. But that may be a hot area, electronics don't like high temps.
Likley will require trial and error. Installed into ferrous metal ( steel) the magnetic field at the sensor may be distorted by the steel. May require playing with gap and timing ( degs before TDC)

You can trial and error it but, If you use the gen's ignition modual likely would be a good idea to position the magnets at least about same radius from spin axis as on rotor. Has to do with how fussy you have to position the modal, smaller radius might be harder to adjust, but you can try it.
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Old 03-05-2017, 10:59:17 PM
bbqjoe bbqjoe is offline
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Default Re: Onan 4GBE spark problem

I'm going to give it a shot.
They should have placed them somewhere like that in the first place.

I recently started working on small 200 cc honda engines.
They mount the magnets right on the metal flywheel without detriment to the signal.
There might be a little adjusting here and there, but I still have one arm attached.
I can put that in a position I can see at TDC, and get pretty close in line where the first magnet should go, then just go 180º and mount the other.

I'm of the opinion they make this so difficult, you just buy a new generator.

If it works, great! If not, it can sit another ten years and not be missed.
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Old 03-05-2017, 11:27:38 PM
len k len k is online now
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Default Re: Onan 4GBE spark problem

I see no reason magnets can't be installed in steel flywheel, just may have to play with gap and maybe angular position to get the timing advance you want.
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Old 03-05-2017, 11:40:05 PM
bbqjoe bbqjoe is offline
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Default Re: Onan 4GBE spark problem

On a small engine, the gap is about a credit cards width, sometimes up to .040.

There's some pretty crazy adhesives out there as well.
One might just drill a hole in the magnets, and another on the flywheel or fan or what ever it's called, then tap for a screw.
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Old 03-06-2017, 08:01:07 AM
Kevin K Kevin K is offline
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Default Re: Onan 4GBE spark problem

If you try this, and you intend to use the original Onan pickup, just be aware of the polarity of the magnets. On the plastic arm, the magnet on one arm is North, the magnet on the other arm is South. One turns the current to the coil on, the other turns the current off and produces the spark. The Onan electronic ignition system is different from most other systems.

On the other hand, if you use another electronic ignition such as the GM HEI system, you need only one magnet to trigger the spark.

The timing on the electronic ignition BGE generators is 14 to 18 degrees BTC.

You might want to consider cleaning the mouse nest and broken plastic arm out of the generator end before it gets caught in the starter gear.
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  #18  
Old 03-06-2017, 10:44:01 AM
bbqjoe bbqjoe is offline
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Default Re: Onan 4GBE spark problem

This is most curious. I have never heard of a south magnet vs a north magnet.
Every magnet I've ever dealt with had a south pole and a north pole.
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Old 03-06-2017, 11:04:21 AM
Kevin K Kevin K is offline
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Default Re: Onan 4GBE spark problem

Same thing. Every magnet has both a north and south pole. On the Onan arm, one arm has the south pole on the tip, the other arm has the north pole on the tip.
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  #20  
Old 03-06-2017, 11:15:11 AM
bbqjoe bbqjoe is offline
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Default Re: Onan 4GBE spark problem

I'm sure I will experiment with this concept.
Somehow I doubt an unconnected entity such as the sensor knows a south polarity passing by it vs a north passing by.

I don't know a whole lot about these things, but I remember we studied magnets one day in science class when I was about ten.
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