allis b or c about 1948 magneto timing

correct · Apr 17, 2015

Last eve tried to reinstall just rebuilt FJ mag on my allis B .I found tdc cylinder 1 then put plug wire in 1 on the cap of mag and rotated till it snaped a spark. The flywheel was on the second mark "C" not the F when I put mag on. Yet it wont start I did hear a pop now and then "has elect start". Question is should I have been just prior to the snap for cyl 1 and on the F mark?. I did not pull cap off to look at rotor cause I had a plug wire in one when it sparks. I also get 3 clicks prior to the plug showing spark,but I suspect if I let it spark then I'm past #1 when I install it

Dick L · Apr 17, 2015

OK, You have two times the C or top dead center will show in the inspection hole. One is on the compression stroke which is the one needed. The second time is at the exhaust stroke which would cause it to be what is called 180° out.
Placing your thumb over the number one spark plug hole you will feel air being pushed out as it comes up on TDC for the compression stroke. If you pre set the magneto to fire the next spark at number one plug wire you would need to back the engine to the Fire line on the flywheel to install the magneto or a little farther to get the drive lugs to fit with out fighting the impulse spring. After the magneto is installed and when the magneto clicks and makes spark to number one you need to see the C line or TDC line in the inspection hole. This is the way I prove I am in time. The fire line would be in the hole when running only when in time.

correct · Apr 17, 2015

thanks Dick I did confirm the compression stroke with my thumb on the hole for pressure--- using the hand crank to rotate so I guess Ill trip it around till I know the next one is cly 1 fire and set it to the F mark just prior to the trip and see if it starts

Dick L · Apr 17, 2015

That is the way I do it. I usually check the magneto in a vise checking all the wire terminals and when four fires I tape the drive so it does not rotate. That way I know the next click will be for number one. I actually don't look for the fire mark or put my crippled hand up to check for pressure anymore. I just watch the rocker arms and magneto drive so the impulse drive will fit.

old · Apr 17, 2015

Throw me an e-mail and I'll send you a copy of the manual for that mag which might help you get it in time

allis b or c about 1948 magneto timing

correct

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Dick L

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correct

New User

Dick L

Well-known Member

old

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