acmoc

ACMOC Membership Benefits

  • FREE quarterly magazine filled with content about antique Caterpillar machines
  • FREE classified listings
  • ACMOC store discounts and specials
  • Full Bulletin Board Access
    • Marketplace (For Sale/Wanted)
    • Technical Library
    • Post attachments

$44 /year ELECTRONIC

$60 /year USA

$77 /year International

d7 17a pony motor magneto timing.

More
10 years 8 months ago #100205 by powersmoke18
I pulled the old magneto off the d7 and noticed an X on one of the two drive te
eth. Would anyone happen to have the instructions for properly timing the magneto.

Please Log in or Create an account to join the conversation.

More
10 years 8 months ago #100252 by Old Magnet
Two different mags were used depending on tractor s/n.
Bosch on the early models, Wico on the later.
Seems you have the Bosch unit.

Please Log in or Create an account to join the conversation.

More
5 months 3 weeks ago #257115 by jrpmccoy
I have one off a D7 17A later SN so it's a WICO. It is either a 7M or 8M that I am working on. There is an X on both halves of the coupler but you need to look close to se the X on the female side.  My service manual does not tell me how to time the thing but judging from what I see on the forum topics here I am going to bring number 1 cylinder to TDC on compression stroke (will look at flywheel on pony also to see it I can see the TDC mark or as mentioned above "engagement bolt" but it wont really be necessary I feel as this thing ran when it was parked 14 years ago) and be sure the magneto has just fired on #1 but not #2 (with it off and me rotating it). It should then go right on and be in correct timing.  Folks have worked on this to try to start the pony for over a decade now. Based on the way the points being adjusted so they were always closed (never touching the cam) and the story on how it had to be "pre-energized" before it would have spark, I think I have a TDC exhaust stroke fire vs a TDC compression stroke fire. Will travel back to the site this Friday and hopefully make some smoke. Not sure if this method/approach gives you any insight but basically a 4 stroke motor has to fire on compression stroke, if no one has pulled the magneto gears or the camshaft drive gears apart since it last ran the it should be timed  if the it up on TDC compression and it has just fired 1 on the magneto. They are saying the it is BTDC firing on the threads I read so that is why I say the magneto should have just fired #1.

Comments?

Please Log in or Create an account to join the conversation.

More
5 months 3 weeks ago #257117 by Old Magnet
Here's how to time the Bosch Magneto, Wico should be similar:
 

 

 
Attachments:

Please Log in or Create an account to join the conversation.

More
5 months 3 weeks ago - 5 months 3 weeks ago #257120 by jrpmccoy
  Powersmoke18, what serial number us your machine? There is another forum post here that shows the 3/8 x2" bolt instructions for TDC. You have to ensure that the valve timing is coming up on #1 TDC compression (all valves closed) finger over the plug hole works to determine compression stroke as the bore is too far offset to use a dial indicator set up. Mine is a newer 17A and I don't have that sideplate depicted.
Attachments:
Last edit: 5 months 3 weeks ago by jrpmccoy. Reason: Clarity

Please Log in or Create an account to join the conversation.

More
5 months 3 weeks ago #257126 by Old Magnet
Late 17A Timing....
 

 

 
Attachments:
The following user(s) said Thank You: jrpmccoy

Please Log in or Create an account to join the conversation.

More
5 months 3 weeks ago #257134 by jrpmccoy
What I find odd is that the repair manual from Cat does not have any of this for the pony, it is only found in the Operators Manual.

Please Log in or Create an account to join the conversation.

More
5 months 3 weeks ago #257135 by Old Magnet
Yes, the 17A service manual has nothing on magnetos. The coverage is much better in the D8, 14/15A service manual. Same magneto's.

Please Log in or Create an account to join the conversation.

More
3 months 2 weeks ago #258462 by TOP
This thread was helpful to me for servicing the magneto for the first time. Somebody mentioned it is hard to see the piston crown hit TDC. I made a little tool from yard sign wire rod that lets me feel for TDC through the spark plug hole while turning the flywheel. It worked reasonably well for me and I  got the magneto timed and it started on first crank. Thanks.

D7 17A '56
Attachments:

Please Log in or Create an account to join the conversation.

Time to create page: 0.176 seconds
Go to top