Briggs 23FBC - Problem solved ???

Did some further testing this AM.
Coil and wiring tested good as well as points using the tips you guys have given me.
But.....as I was testing I noticed I can GET GOOD SPARK by turning the flywheel BACKWARDS.
Just to confirm, all briggs motors turn clockwise when looking from front of motor - correct? (carb to the left).
Assuming this is correct, and I,m getting spark when rotating the flywheeel backwards, this tells me its a timing issue.
The timing marks line up so to me this means the armeture piece mounted on the crankshaft has slipped or spun away from where it should be.
Am I on track with this diagnosis?????

Tom, it must have "Magna-Matic ignition"?

If so, did you look at the link Joe posted in the original thread to the Magna-Matic instruction page that explains how to time the "rotor" to the crankshaft?

Below is a link to even more info. (.pdf)

Magna-Matic info is on .pdf pages 37 though 41.

http://www.google.com/url?sa=t&...XEdhOiBEDmz6il5nfqA&bvm=bv.70138588,d.aWw

My memory is not quite what it used to be but I believe there was a Briggs model 23 that had reversed polarity. I remember we could sent the flywheel in to Briggs and they would reverse it so we could use the electronic ignition.

Yes it is a Magna-matic.
Your PDF wasn't attached.

Do you have coil installed correctly on core & are coil primary connections connected correctly?

Look at pic(fig 44) of armature assembly/coil in link I provided,plug lead must be on left side of armature assembly,also small single lead on plug lead side of coil must connect to insulated terminal with point lead & double wire coil lead connects to ground screw on flywheel back plate,from what you say about turning flywheel backwards(ccw)and getting spark could be an indication of reverse polarity on coil primary connections.

There were two different style rotors used on these eng,on older eng there is a set screw that threads into rotor & goes into a hole in crankshaft & a locking screw on face of rotor to lock set screw,newer eng have a clamp collar on face of rotor to lock rotor to shaft,both style rotors use a woodruff key to time rotor to crankshaft,while it's rare key may be sheared.

Yes The wires are connected correctly and actually it would be hard not to have them correct the way they come out of the coil. Attaching a couple pictures.
I'm assuming all motors rotate clockwise correct?
Did you ever hear of this happening if the armature has broke the woodruff key and moved slightly?

I don't think rotor key is the problem,looking at pics you posted I can think of two other possible causes of ign problem.

1-eng may be designed for a specific use/application depending on equipment same mounted on,eng may be reverse rotation for use on military generator/standard generator or equipment that has a left hand turning pump/transmisson connected to eng.A tip off for eng rotation direction would be flywheel vanes,if top of vanes curve to right eng turns CW if vanes curve to left then rotation CCW.

2-looking a one pic eng appears to have a belt drive generator or starter generator,given age of eng same is probably 6v,many old 6v systems were pos(+) ground rather than neg(-) ground,if you're useing motor/starter generator to crank eng rather than rope start try reversing battery polarity,you may be spinning motor in wrong direction,if you have spark after reversing battery polarity put a shot of carb cleaner/gas into carb & see if eng fires/runs.

Joe,
First of all thanks for your input on this. I've done a lot with various engines but not much with ignition systems.
I'm attaching another pic. showing flywheel fins which would confirm its a CW rotation per your description. Also checked the rotation with it in gear on the tractor its on and this cofirmed the CW rotation as well. (Just bought this 1948? Shaw tractor so I'm just getting into the restoration of it)
I've been turning it over by hand to check the spark so the starter you see in the pic. isn't a factor.
Tonight I checked the magneto armeture woodruff key and alignment screw and they were fine.
I also tried reversing the small leads on the coil by extending the wires and this did nothing.
So still have great spark when turning crankshaft backwards only.
Any other thoughts?
I'M STUMPED.

I can offer only two more suggestions.

1-check that plug lead long enough & try reversing coil on core so plug lead now on right side of armature & lengthen coil/ground leads,it's possible you have wrong pn coil for your type# eng.

2-if reversing coil on core doesn't cure problem,then do a google search shaw tractor history,in addition to several websites showing history of company & utube links there is a link to a shaw tractor club in NH,they may be able to help you more with eng info as this may be a common problem with this eng.

Tom, did you ever look back at my previous post... I corrected the link to the service manual.

If you have looked at it, did you "time the rotor", as is explained on (.pdf) page 40?

Spark occurs at the instant the breaker points OPEN.

With a magneto system, for hottest spark, the points need to open (break) at the instant the current in the coil windings is at it's peak due to the position of the magnets passing them.

If this relationship is not correct, your not gonna get a GOOD spark, at the right time.

If it sparks going backwards, that would be caused by a timing error between the points and the magnets/coil.

If there is not enough adjustment in the slots the coil assembly mounting bolts pass through to make the timing marks line up at the exact point the the points "break", it would seem the camshaft (which operates the breaker points) is not timed correctly to the crankshaft.

Since you HAVE spark (when turned backwards) and this is a simple breaker point (non-electronic) system, you need to look past the electrical parts, and focus on the breaker point-to-magnet/coil timing.

I hope I have typed this up clearly enough to be understandable!

Post back and let us know what you figure out!

Bob,
Yes I did take a look at the info. and checked the timing of the armature to the outer field. It was timed correctly as far as I could tell. the mark on the outer steel was tough to see. The piston travel seemed to coincide about right also.
And As I said I checked the woodruff key and that was fine so what gives?
I called the place I bought the coil from and they suggested flipping the mounting of the coil. I don't know if that will be possible as there isn't a lot of room under the flywheel as you know.
I will also re-check the mark on the outer field to make sure of the timing once more.
I'm feeling good about the nice blue snapping spark but doesn't do me much good at this point.
Thanks for your help.
I'll keep you posted.

I don't believe flipping the coil will help (it might if it was a newer unit with electronics involved).

Watch the movement of the breaker points/verify their opening with a meter.

As you rotate the engine in operating direction, the piston should come up on TDC on the compression stroke, the points should "break" and the timing marks should line up, all at the same time!

I'll pull the head and verify all.
Thanks

What's the type# of eng? Might help instead of keeping it a secret,even within same mod# of eng there are different parts/pn depending on type# of eng.

Type is 203540, SN is 34097
No secrets here. Just want to get it running.

No one has been able to look this up to tell me its age.

Usually when I tell them the Model No., they say "No - I need the Model #" And then they say "OH - that must be really old". HA

I"m out of town this week so won"t be able to get back to this until the weekend.

I am FAR from an expert on dating these old engines, but looking at the ASECC site, 23 series, "FBC" = flange mount, ball bearing automatic choke.

Does it have automatic choke?

A S.N. of 34907 would date it to May of 1950.

http://www.asecc.com/data/briggs/briggsid.html

http://www.asecc.com/data/briggs/data4.html

Thanks Bob

It does appear it had auto choke originally as there is a shaft that runs from the choke baffle into the flywheel area, but there is nothing connected beyond this.
It is now set up with a manual choke cable.

Bob,
Another day of trying to figure this out with no luck.
I took the head off, put my ohm meter on the points with the wire disconnected, and watched the timing mark. All were in sync.
And yet no spark.
I even replaced the wire from the points to the coil just to make sure it was not the problem.
By the way the valves and piston look great. Just the expected amount of carbon deposits.
So after all this I tested the coil windings again and got 0.5 ohms accross the primary and 9.6K ohms from the Spark plug cable to the small leads.
From what I've read the primary should be higher than this.
I think I might have a bad coil. That is I hope I do to finally solve this.