720 timing mark
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Garden Tractors
Forum Description: A great place to discuss the Simplicity and Allis Chalmers Garden Models
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=153770
Printed Date: 22 Feb 2025 at 11:16pm
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Topic: 720 timing mark
Posted By: BrianC
Subject: 720 timing mark
Date Posted: 07 Sep 2018 at 6:00pm
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The front of the engine has a timing pointer tab. I guess the timing mark is on the front pto clutch? What does it look like, steel stamp, engraved line, thick or fine. Is it a TDC mark or the 20 degree advance mark. So far I haven't found it. Need a clue. Sure do miss a hand crank. |
Replies:
Posted By: AcFordHawk
Date Posted: 11 Sep 2018 at 8:51pm
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Brian, If you haven't found the timing mark info, here are a couple pages out of the 4041/620 manual I have which should help. The whole PDF file is too large to post. uploads/610/Doc1.pdf" rel="nofollow - uploads/610/Doc1.pdf uploads/610/Doc2.pdf" rel="nofollow - uploads/610/Doc2.pdf ------------- IB (restoring), MF GC1705, MF 2705E |
Posted By: BrianC
Date Posted: 12 Sep 2018 at 11:04am
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I think I shall write a book entitled "Allis-Chalmers Timing Marks and Me". I also made a project out of timing my C with magneto. See my attached picture, looks clear as a bell now, doesn't it? First, thanks Paul, your images helped me find the "T". I used paint remover and cleaned it all up for the picture. So I have a 620, but my user manual is for a 720. I have deduced that the 720 has a different front PTO clutch, with a safety brake on it. This equipment obscures the timing marks. The 720 manual pretty much says have the dealer set the timing, they have the proper equipment. The 620 manual is actually telling you how to set the timing yourself. In the picture, taken from the left side of tractor, the engine is to the right, you can see the timing marker tab. You can see the (20 BTDC) line engraved in the PTO body. That is your timing light target. Below that is T A C, with the A actually a chevron to indicate top dead center (also note lack of engraved line). With the PTO being 6" diameter, it is in the correct place to the 20degree mark, a hair over 1" peripheral distance. The engine rotates clockwise when viewed from the rear. Think about that, then look at the figure 31 from manual scan. I say the figure 31 image is incorrect, they put the pointer tab on the wrong side. It should be on the right side of the image, not left. And also my real life example picture is showing a rectangular tab, not pointed. I think my machine may be a put-together from different years of Allis, Simplicity and Onan parts. And oh, when I check the timing, it was about 16 degrees, I adjusted it to 20. Not much of a difference as far as I can see.  |