Distributor timing

Glen said:
There is a gear on the end of the distributor shaft that runs the distributor. A pin holds the distributor gear to the shaft. The pin may have come out, or is broken, letting the shaft turn to different positions. I think someone on here had a problem with that in the past, but I'm not sure.
Below is a page from the Cub parts manual showing the distributor. The gear is number 7 in the picture, it doesn't show the pin, but shows the part number of it at the description for 7.
Click to expand...
When I had mine out it was staked on both sides. I had to take mine out and reinstall when I rebuilt and cleaned mine, I tried to stake it back best I could. I offen wondered what would happen if it fell out???
 
I've been sick for a couple of weeks but finally got back to working on the Cub. Not having any luck though. I did everything in the book and even tried a couple of ideas from others. I can hand crank it and on the compression stroke on #1 cylinder the timing mark is on the pointer. I verified that it was the compression stroke by using a compression tester and then seeing that the cylinder is at the top and both valves are closed. I have done it several times and the timing mark is on the pointer every time. The cylinder is at TDC because I can see it through the spark plug hole. However on every cycle of compression the rotor on the distributor advances so ignition doesn't happen. On consecutive cycles of compression the rotor stops in a different location. There is no play in the distributor gears. I also held the rotor while turning the crank and did not feel any skipping. I did pull the distributor and it is a 32 tooth gear. It is not an original distributor and I'm beginning to suspect that may be the issue? Still working on it.
 
Attached are photos that show the rotor advance on consecutive cycles of #1 cylinder being brought to TDC . The rotor advances on each cycle rather than being at the same spot each time.1768593801574.png1768593759104.png1768593711166.png1768593635282.png1768593589368.png
 
The distributor turns at half the speed of the crankshaft, so the rotor should be 180 degrees from where it was at the last TDC. Two revolutions of the crank will put the rotor back where it started. Your photos make it look like it's not even moving 180 degrees, tho, unless I'm not seeing it correctly.
 
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Your distributor looks like a replacement unit that is available all over the internet for prices from about $65 to $290. Presumably, it is a drop-in replacement that should behave the same as the original. The details that have been posted here such as those relating to how the gear is mounted etc. may not apply. It probably has a 24 degree advance rather than the 16 called out for a Cub. But that is the least of your problems right now.

Are you saying that EACH of the above pictures was taken with the notch in the pulley in line with the timing pointer? The rotor should turn at EXACTLY one half the speed of the crankshaft. When cylinder 1 is at TDC compression, the rotor should be pointed at about 1 o'clock. If the crankshaft is turned one full revolution, the rotor should then be pointed exactly the opposite direction to about 7 o'clock. One more crank revolution should bring it back to 1 o'clock. If that is not what is happening, there must be some failure in the mechanical drive from the crankshaft to the distributor.

If you are not getting the exact 2:1 ratio, pull the distributor back out and post a picture of the gear on the bottom of the distributor. If that gear looks good, pull the distributor adapter (which does the 2:1 speed reduction). See if there is a problem with the gears/shaft in that area. When it is removed, the shaft in the front of it pulls right out (usually falls out if you point it down). It has the gear that drives the distributor. Post a picture of it.
 
Yes, each of the pictures was taken with the notch on the pulley in line with the pointer. They were taken after two revolutions and on the compression stroke and the cylinder was at TDC. I have had the distributor and the adapter out and they appear to be good. While inserted I held the rotor and turned the adapter and did not get any slippage. I have cleaned the gears up for the pictures. Thanks for your help!


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I assume that you have also taken the rotor in one hand and the gear on the bottom of the distributor in the other hand then twisted, wiggled, pulled etc. in every way imaginable to confirm that the rotor and that gear are totally connected as well. You should be able to put a clockwise twist on the rotor and gear and get a slight movement (a few degrees), and a spring force should push them back to the original position. Other than the few degrees, they should be tightly coupled.

Next place to look is in the engine where the T-shaped end of the shaft pictured above engages the drive slot. With the crankshaft turned to TDC, that drive slot should be oriented at about 2 and 8 o'clock. If it isn't, that in itself isn't a problem. Just note where it really is. The drive slot should turn at crankshaft speed. Verify that with each 1/2 turn of the crankshaft the drive slot also turns 1/2 of a revolution bringing the slot back to the original position. You might want to get a helper to slowly turn the crank while you add a little resistance to the slots rotation. Make sure the piece with the slot has no side or up/down movement.
 
You might not want to do this until you’ve exhausted all other options. But last resort, you might want to check to see if the idler gear that drives the governor behind front cover is still tight.
 
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