641 timing

Remove the cap etc. etc etc.

Leave rotor on.

Loosen the two bolts holding the Distributor clamps to the block so you can turn the distributor to adjust timing.

Remove plug number 1. and note where plug number 1 should be according to your distributor cap.

Gently feel the wire into the chamber through the removed sparkplug hole, and at the same time, assuming your fanbelt is snug enough (tractor in neutral and THE BATTERY DISCONNECTED turn the fan blade thus turning the motor over by hand.

After some turns of the blade, you will feel the piston hit the end of the wire and push it up or, as it drops down the wire should slide inward a tadbit.

You could loosen the other plugs so you are not fighting compression if turning the fan blade by hand.

Keep turning until you get the feel of it, and the wire sliding up and down. When the wire reaches the top make a small mark on it. That is TDC either in compression (which is what you want) or in exhuast or very close to it..

Note the rotor location. It should be at number one according to the cap or, 180 degrees off..opposite of where it should be in TDC 1 Compression Rotor at #1 plug wire..

Turn the blade until you get the rotor at #1 according to the cap.

Tighen up the plugs, replace the plug. Install wires and cap. Gently snug the bolts holding the distirbutor to the block but loose enoough to turn the distributor as it is idling.

Give it a try fire it up...

Either it will fire right up, or it will want to fire up, but may spit and cough and wheez and snort, and backfire and sound like you just kicked a sleeping wild pig in the hind end. If it does that...your 180 degrees off.

If it fires up and runs, just slightly turn the distributor as it is running one way or the other until you can time it and tune it by ear. Turning it too much and you will hear it bog down, and turn it the other way too much and it will bog down. Practice it and find the inbetween place where it hums and evens out niceley.

You can practice this easy enough. After a small while you will find this is very easy and now if I remove the distributor and forget to mark the rotor I don't fret about it. It works for me in a couple minutes or less.

Good luck.

The other method as Tlak describes is to keep all three plugs tight but remove plug 1 and as you strecth to reach the starter button and push it, you can feel the compression over the hole if you stretch and plug that hole tight with a finger. Just do short quick burst of the starter button as you feel this.

You can do that at first, then you will know you are in compression...then do the wire method turning the fan and the next time the piston comes up it will be in exhaust, and then turn the fan some more until the wire moves up and you're back into compression.

As you try it, and think about it as you do it, it will come together for you easy enough. It just takes a little patience and practice at first. But you will get it. Believe me, if I can do that, you can do it!