Timing question for an M

I am trying to get my M started after sitting 6 months. It was running when it was parked. I re-wired it with a 12 volt system according to Bob M's schematic and have fire to the points. It backfires through the breather. I lined up the the pointer with the first of the pair of notches on the compression stoke and find the rotor button is pointing straight toward the ceiling. The question is, has this distributor been installed at some time a "cog or two off"?
I have fooled with small-block chevy engines for 40 years and know that if gears are not line up right you can get a cog off. This tractor never would idle down like it should, so I was wondering if a mal-aligned distributor could be part of the situation? I have a manual for this tractor but thought someone may have a trick up their sleeve. Thanks.

I'm assuming that since you suspect the timing to be off you have had the distributor off recently?

The distributor should have enough rotation available to correct for being off by a tooth. You could try loosening the two bolts holding it in place and rotating it by hand to time it if that's the case.

Otherwise it may be a case of the spark plug wires being mixed up. I've run in to this myself. The drawing in my original manual for my H has an isometric (3D) drawing of the distributor cap showing the location of the plug wires. I found it to be a little difficult to interpret. I felt that a top view of the cap would have been simpler to understand.

just my thoughts.

This is a very "general" answer only, may or may not help..

Iffffff the distributor is timed correct, if you get No 1 cylinder to TDC on its compression power stroke, the rotor tip should be pointed close to the No 1 cylinders distributor cap internal pick up and the points just breaking open.

IE Id first get the No 1 to TDC on compression power,,,,,,,,,,then insert the distributor in such a manner that the rotor tip is lining up with where the caps internal No 1 cylinder pickup is located, and that should also be where the poinst are breaking open.

Sorry, thats all I have to offer

John T

A couple possibilities:

1 - The distributor drive is installed off a tooth or two (presuming you've removed/reinstalled the distributor). With the #1 cylinder on compression and crank at TDC notches #1 the rotor arm should be directly under the #1 tower on the cap - which is about at the "1 o'clock" position.

Alternatively, with #4 cylinder on compression and the crank at the TDC notches, the rotor should be directly under the #4 tower on the dist cap.

2 - You've got the plug wires installed 180 deg out. Working clockwise around the distributor starting at #1 the plug wires should go to 3, 4 then 2.

Hope this helps!

The Operator's manual has very detailed insructions as to how to time that engine. I don't believe you have one, or you would have followed that procedure. If it is a timing problem no one on this forum can give you better instructions than that -- explain them yes. Basically put # 1 at the top of the compression stroke. To be sure you are not a tooth off, remove the distributer. Turn the rotor so that it points to #1 on the cap, #1 should be marked on the cap--top right viewed from the rear. Install the distributer without moving the rotor. Rotate the distributer counterclockwise. Remove the coil wire from the distributer cap and hold it close to the nut on the distributer body. Rotate the distributer body clockwise until you get a spark -- it should be in time. If you can still hand crank it (crank mechanism is frozen on many due to lack of use), hold or attach the coil wire next to the nut and do one complete revolution until it sparks. Timing marks should be very close or exactly on the 1st of the double notches. If this does not work, you have other problems, anything from a loose distributer shaft to problems with the cam gear (not likely if it ran 6 months ago).

I have not had the distributor out yet but I will if necessary. Right now the marks and pointer are lined up, I'm on #1 compression stroke, the rotor is pointing to 12:00 o'clock , but the #1 position on the cap for the #1 wire is about 2:00 o'clock. Is it possible someone timed it using that other single mark on the crank pulley? I will have to pull the distibutor find that out, right? thanks.

As long as you are sure that #1 is at the top of the compression stroke and the marks are lined up, the distributer is no big deal to pull out and replace. I didn't think it would fire at all with it that far out of time. Be sure that the distributer shaft is not loose and that the points are set a 0.020. Best to set the points with the distributer out.

(quoted from post at 13:00:41 12/18/10) As long as you are sure that #1 is at the top of the compression stroke and the marks are lined up, the distributer is no big deal to pull out and replace. I didn't think it would fire at all with it that far out of time. Be sure that the distributer shaft is not loose and that the points are set a 0.020. Best to set the points with the distributer out.

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He could be that far out if the wires have been moved in the cap. Have you verified which spot has the wire to #1?

Just because #1 is marked on distributor does not mean it is actually wired that way. Have seen them wired with #1 in every hole in cap runs just as well that way just makes it hard for next person to check it out.

Thanks, for the help. Got it running. CNKS, you were right. The previous owner had the wires on the distributor cap rotated clockwise one hole.
Merry Christmas!!!