B mag timing

Nick m

Member
Alright. More questions. I was not getting
the mag timed, and I think I see why. I
read on another forum that the drive should
be horizontal when #1 is tdc, which #1 is
tdc in the pic. Did the thumb over plug
hole, watched with a pen light until all
the way up. The timing mark on the fly
wheel us off too. Fire mark is slightly out
of window when tdc. I was told this engine
was assembled by some Ffa kids years ago.
I'm thinking they got something off a tooth
somewhere. Can I simply pull the governor
cover and correct the drive issue? Are
pieces going to fall everywhere? I'm a
little over cautious on stuff like this,
but hate to mess stuff up. Thanks
a255185.jpg

a255189.jpg
 
When #1 is TDC on compression, the CENTER mark on the flywheel should show in the opening. The FIRE mark should show 30 deg BEFORE TDC. See the link. There is a dwell in piston movement at TDC and you may not be stopping where you should just by observing the piston top. Just make sure you are on the compression stroke with your finger and slowly continue rotating the engine until the CENTER mark appears in the opening. It's easy to go past the correct point so you must go a little at a time. Then see where the magneto drive lugs wind up.
B Mag Timing
 
The "FIRE" mark will not be in the window because it is advanced from TDC. I use a compression gauge in #1 cylinder (front) and then get it to TDC from there. Looking at the rear on the mag #1 wire is upper left. I turn the mag by hand until the rotor clicks past past #1 point then back up the rotor slightly and move the coupling enough to mate with tractor and mate it. Should be good to go.
 
On a "B" There should be a timing mark on the back side of the governor gear that shows you the proper mesh with the camshaft gear. If you remove the governor cover (be careful when removing the thrust bearing) you should see the mark. A service manual would tell you more. I would make sure that is timed correctly before trying to time the mag. A service manual will also tell you how to get the timing correct by using the fire mark on the flywheel. If everything is properly meshed, the drive lug on the mag will match the drive sprocket on the tractor.
 
If your working on this like I usually am i make sure I’m on the compression stroke then insert a drinking straw into the plug hole as the cylinder comes up the straw will move and level out as it gets closer to TDC then start looking for timing marks on flywheel. Works really good on these old allis’s where it’s on the opposite side of the tractor.
 
If your working on this like I usually am alone i make sure I’m on the compression stroke then insert a drinking straw into the plug hole as the cylinder comes up the straw will move and level out as it gets closer to TDC then start looking for timing marks on flywheel. Works really good on these old allis’s where it’s on the opposite side of the tractor.
 

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