F12 starting issues

[junkpile]

Still working on 37 f12 and can't get it to start. Getting good spark and have reset ignition timing several times but wonder if I'm still off. Currently, when #1 cylinder is at TDC based on flywheel mark (DC 1-4), the distributor rotor is contacting #1 and points are opening when nearly fully retarded. The impulse doesn't snap until a little past TDC however. I have good compression and have put gas in both carb and cylinders but nothing. When I had the timing retarded more, got it to pop once but that's it. I have attached picture showing rotor and points just after impulse snapped in current setting. Not sure if my timing is still off or need more or less gas. Any advice appreciated as I'm getting tired of cranking.

 

[Fritz Maurer]

The easiest way to do this is to forget about where the points are entirely, and concentrate on getting the impulse to trip precisely at DC 1-4.

Draw a line across both halves of the timing coupling, with a paint pen, so you don't get lost. Then advance the coupling one bolt hole at a time ( you said it was snapping after TC) , until it snaps right on the DC line. Then set the points and you are done.

 

[560Dennis]

Verify the location of number one cylinder for your tractor.
Teaspoon of fuel in each cylinder , it should put put .

 

[rustred]

Here , very simple. Have someone very slowly crank it while u hold a piece of wire or screwdriver to feel the piston coming up. The trip or spark should happen once at TDC. Don’t matter what piston as all 4 will click at TDC. Then u fine tune the spark with them 2 1/4 inch bolts in the coupler.

 

[junkpile]

So the impulse needs to trip right at TDC? Seems like I may need to retard it a little so impulse trips a little earlier.

 

[junkpile]

Sorry Fritz, didn't see your reply initially. You say I need to advance one hole at at time. Is advancing impulse same direction as distributor rotor?

 

[Fritz Maurer]

Don't pay too much attention to the distributor rotor, other than to find number one, as it rotates in the opposite direction and confuses the issue and it has nothing to do with the impulse coupling anyway.

The timing coupling rotates the same direction as your hand crank. If you say it's tripping a little past TC, then you have to rotate the magneto half of the coupling in the opposite direction one hole. Then make two full revolutions of the hand crank and see how far you are from the TC mark when the impulse snaps on the second revolution. The distributor rotor should be back at no. 1 position.

For the utmost in precision, you should use a hydraulic jack under the hand crank, when the impulse is about to snap ; as it is impossible to stop the rotation of the crankshaft promptly after the coupling trips, when turning it by hand, no matter how careful you are. Almost certainly you will go past the mark due to the sudden reduction in turning force after the coupling trips.

 

[rustred]

So the impulse needs to trip right at TDC? Seems like I may need to retard it a little so impulse trips a little earlier.

Well where is it tripping now. We need info.

 

[Fritz Maurer]

Im having brain fade ... I think maybe you move the magneto AHEAD to bring the mark BACK, if it's past. In any case, it will be readily apparent after the first try.

 

[rustred]

As I say you have to be pretty much stopped with the crank when it is ready to trip. No way the engine is going turn ahead more. I have done lots like this. But gotta know where your at before you start screwing around with the coupler holes.

 

[rustred]

To advance the timing you got to back up the mag.

 

[rustred]

My W 12 starts with one click of the mag and moving the crank so slow like a 1/4 turn. That’s after shut down and a restart. Cold starts very easy also.

 

[rustred]

To advance the timing you got to back up the mag.

Now i think I got this backwards. You need advance the mag ahead or backup the engine when coupler is disconnected.

 

[Pete in Holland MI]

Take the valve cover off so you can watch the valves. This'll ensure you are coming up on compression, and not 360 degrees off. A 1/4" dowel is better to lower into the #1 cylinder to verify it is coming up to TDC than anything metallic. Set the mag handle all the way up to turn the mag off, then lower it at the loop about 1/8". Adjust so the impulse trips at TDC, or a degree or so afterwards. Ensure the rest of your wires are exiting the distributor cap to the appropriate cylinders.

 

[rustred]

Take the valve cover off so you can watch the valves. This'll ensure you are coming up on compression, and not 360 degrees off. A 1/4" dowel is better to lower into the #1 cylinder to verify it is coming up to TDC than anything metallic. Set the mag handle all the way up to turn the mag off, then lower it at the loop about 1/8". Adjust so the impulse trips at TDC, or a degree or so afterwards. Ensure the rest of your wires are exiting the distributor cap to the appropriate cylinders.

The spark plug is already out , no need to remove valve cover. And that is just more info for him to get all mixed up in. Watching running mates valves. A pop straw also works.

 

[junkpile]

Appreciate all the ideas. Moved the coupling one hole and now impulse snaps right at TDC. Getting good spark, have good compression and have set valve clearances to 0.013. Added about 1 tsp gas to each cylinder like 560Dennis said and .....nothing. Pulled plugs, checked spark and tried again....nothing. Poured some gas in carb and cranked...nothing. I am out of ideas. Everything else I've ever worked on if you have gas, compression and spark at the right time it should fire. Valvetrain is moving appropriately. In case it matters, I rebuilt this engine about 15 years ago and got it to run but then it sat.

 

[Fritz Maurer]

Try a few pumps of oil in eachcylinder. Raw gasoline washes the oil off the cylinder walls and may interfere with compression.

 

[rustred]

give it a pull !

 

[rustred]

Hope u have it on the compression stroke for number one , or she ain’t gonna start. Remember there is 2 top dead centres at the same time.

 

[junkpile]

Watching valves, it's compression. Intake valve closes and then piston comes up with both valves closed. I've pumped oil into cylinder a couple times since it sat. Was worried rings had seized. Think I'll put compression tester on it, but it will blow thumb off spark plug hole and sucking well through carb.