Farmall B Timing

Eric Skokan · Feb 23, 2009

I bought a B this winter to use for cultivating. I grew up on a B on my grandfather's lap on his farm. I just made the rookie mistake of taking the mag/rotor cam gear out without marking it first and now it won't start. Is there any relationship in the rotor position to the mag spindle position? Or do I follow the regular proceedure of finding TDC on #1.

Also, I've read that it's possible to fine tune by ear after that. What does that look like? (sound like?) Thanks.

Bob · Feb 23, 2009

1.) The rotor gear and the little gear next to the cam that drives it are MARKED.

To see how that works, paste the link below into your browser and go to Pages 51 and 552.

http://www.cleancomputes.com/Cub/Blue%20Ribbon%20Service%20Manuals/GSS-5035%20Service%20Manual%20Magnetos/index.html

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/IH/IHmagTIMING1.jpg">

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/IH/IHmagTIMING2.jpg">

2. The timing marks on the flywheel and the casting ahead of it (at the bottom) should just be in register at the moment the mag's impulse snaps.

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/IHabsTimingMarks.jpg">

Setting the mag timing EARLIER than this will cause "kickback", which will break the starter, either YOU or the electric version.

Oldiron29 · Feb 23, 2009

Eric, Pull #1 plug Front plug on engine
Hold your thumb over it crank by hand till you feal out pressure. That is #1 compression Some times you can put a long screw driver in plug hole and watch the piston come up till top dead center Than set rotor to #1 plug in cap that should get you back where you need to be.
oldiron29

Bob · Feb 23, 2009

Since he has messed up the rotor drive gear timing INSIDE the mag, he has to reset that first.

Then, finding the timing marks and getting the timing set @ TDC so it doesn't kick is the correct and accurate way of setting the timing, and NOT hard to do.

Anonymous-0 · Feb 23, 2009

He pulled out the mag gear so now he has to put it back so the timing marks line up before he finds out TDC

Eric Skokan · Feb 23, 2009

well first a friend and i made a crank because there was none when i bought it Then I reset the rotor spindle to the mag gear lining the R on the rotor spindle to the notched tooth on the mag gear (because the rotor spins clockwise) I hand cranked the motor to tdc on compression stroke Then I replaced the cover, rotor, cap, etc. But no dice. It doesn't fire.

So, I pulled the #1 plug and turned it over to see if it would spark. But no spark. (does it have to be grounded really well or perhaps not at all?) I just layed it on the govenor.

I'm wondering which direction to look next. I'm thinking I either did a poor job of finding TDC and have the timing wrong or somehow I've caused the magneto to not generate a spark. How does one test a magneto for spark independently of the timing of the engine? Also, I've noticed that the magneto wants to trip a few degrees after where I think TDC is. Is that normal?

By the way, thank you all for the help thus far. I am very greatful.

Farmall B Timing

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