Model A wico c mag

[Tstoner]

I am finishing up restoring my 44 A. I got to start it for the first time today. I ended up pulling it to get it started since I was tired of cranking it by hand for a while. My question is regarding my wico c short lug mag. After starting it by pulling and running it for a solid 5 minutes I shut it off then tried to crank it by hand with no luck. When I got the mag I set the lag timing at what I thought was 25 degrees. Problem is I have heard conflicting info on what degree the center mark is. Also not sure what degree drive cup I have since there are no identification marks on it. I understand it could be a carb adjustment issue too but I want to start at the mag and make sure everything is timed right.

 

[golfcartman]

Pull the plugs out and ground them to the frame and turn the flywheel and see if it is sparking when its supposed to. May need another set of eyes. It sure
makes it easier. If its sparking before or after TDC. then you will need to retime the mag to the tractor.

 

[John T]

Problem is I have heard conflicting info on what degree the center mark is

Best I recall NO WARRANTY top center represents 12 1/2 Degrees on most JD Wico drive
cups UNLESS its a 6274 Drive Cup in which case top center is 2 1/2 degrees. Lag Angle
is to set how much the start time LAGS behind run time, so if the cup is a 25 degree
running the lag angle needs set for 25 degrees of lag (want her to start at TDC)..
If a 6274 25 degree cup that would be 4 1/2 marks to left, on other 25 degree cups 2
1/2 to left

REGARDLESS of all that for starting the mag needs to snap/fire at TDC (LHI on
flywheel at 3 o clock by mark on tractor) if before she kicks back if too late harder
to start.

John T Been a long tine so ???????

 

[Tstoner]

(quoted from post at 05:34:36 07/16/23) Problem is I have heard conflicting info on what degree the center mark is

Best I recall NO WARRANTY top center represents 12 1/2 Degrees on most JD Wico drive
cups UNLESS its a 6274 Drive Cup in which case top center is 2 1/2 degrees. Lag Angle
is to set how much the start time LAGS behind run time, so if the cup is a 25 degree
running the lag angle needs set for 25 degrees of lag (want her to start at TDC)..
If a 6274 25 degree cup that would be 4 1/2 marks to left, on other 25 degree cups 2
1/2 to left

REGARDLESS of all that for starting the mag needs to snap/fire at TDC (LHI on
flywheel at 3 o clock by mark on tractor) if before she kicks back if too late harder
to start.

John T Been a long tine so ???????

Yes as far as getting the impulse at TDC I got that. But setting lag angle is the issue I don't know what drive cup I have since there is no identification is 25 degree more common than a 35 degree cup?

 

[John T]

Ive seen more 25 than 35. Regardless as 35 was used often on the older (Unstyled)
low compression low octane kerosene or tractor fuel which is seldom used, I think 35
is too fast for gas use so I prefer to time at 25 BTDC running regardless. No idea
which one you have, Id guess 25 if a styled A, if unstyled dual fuel maybe 35

Here is a bit of info I found: BUT DONT TELL WHAT DRIVE CUP YOU HAVE SORRY

MAGS

John Deere Model A Tractors
Serial Number: 410,000 to 424,024 Fairbanks Morse FM RV-2A
Serial Number: 424,025 to 466,399 Fairbanks Morse FM RV-2B
Serial Number: 466,400 to 478,499 Edison Splitdorf CD
Serial Number: 478,500 to 487,999 Wico AP 477B
Serial Number: 488,000 to 598,499 Wico C 1042
Serial Number: 598,500 and up Wico XH 1042

DRIVE CUPS

2040 20 deg used on C, XH909 on LA, L
and for the Waterloo tractors
2061B 30 deg short lug
3565 35 deg short lug
6274 25 deg short lug
3744 35 deg long lug
4702 35 deg long lug, usually on base mount mags for early D's
7596 25 deg long lug, used for running D on gas

John T

 

[dan_41jdh]

Hi John T - we've had this discussion before, but just to review: John Deere's SM-2029, page 70-30-9 does state the center mark on the WICO C and X mags corresponds to a 12-1/2 degree lag angle, but both the WICO C and WICO X manuals both state the center mark represents a 13 degree angle (except for the 6274 drive cup on a WICO X which represents a 3 degree lag angle). Regardless, that 1/2 degree discrepancy certainly won't make any noticeable difference. It's interesting to note that the SM-2029 suggests always setting the lag angle 4-1/2 marks to the left of center for either magneto, and that service manual doesn't mention the various drive cups that were available...

 

[John T]

Yeah I got that 1/2 info from a mag rebuilder I know and the late Duane Larson, I wouldnt bet my life one way or the other lol I forget all the sources (more than one) where all I got the 2 1/2 Top for 6274 cup versus 12 1/2 Top for others, but believe its right???

Come to Half Century or Flywheelers !!!!!!!!

John T