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Discussion Starter #1
I've got a Wico magneto that I want to ensure the impulse timing is correct on. Can anyone send me a pic (or just clue me in) as to where my timing marks are supposed to line up inside the magneto? Thanks.
 

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Check gravelymanuals.com. The site isn't responding right now, but when it's on line, you can download all sorts of manuals, including info on mag timing.

Are you talking about changing when the impulse releases, or timing the ignition to the piston?

Briefly, on a Wico you'll see a mark in one side of the drive end, and a dot on the outside of the case. Some units have two dots next to the one dot. Set it up so the timing mark on the drive matches the dot about at TDC. Then for fine adjustment, turn the engine forward until the impulse snaps. That should happen right at TDC.

The two dots should match the timing mark when the piston is about 5/32 BTDC. But that's less important than getting the impulse to fire right at TDC.

I don't know of a way to alter the internal timing of when the impulse releases. It's a simply mechanical pawl, I don't think there's way of adjusting it other than bending or grinding it.
 

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I've got a Wico magneto that I want to ensure the impulse timing is correct on. Can anyone send me a pic (or just clue me in) as to where my timing marks are supposed to line up inside the magneto? Thanks.
Sounds like you are setting the lag degrees as shown below. They under the dust cover. This is what I did without finding a written text. After pulling the covers of 3 mags I had in a bucket, I adjusted mine to 5.1 lines from the right as shown below. Counting started at the first line.

Tractor runs with the first snap of the mag so if I am off the written setting it is not that far off. I am sure someone has the written settings.
Good luck, RB in RI
2450413
 

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Discussion Starter #5
Thanks guys. Yes, I'm setting up lag angle inside the mag. I had heard from the previous owner he had done some fiddlin' around in there. And he did in fact have it retarded.
 

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Well, you learn somethign new every day. I never realized that was adjustable. Thanks!
 

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Discussion Starter #7
What I’ve been learning is that for the Wico on a Gravely you need to be, and take this with a grain of salt because I am no expert, you need to be half a tick to the left of the timing mark that it straight up at 12 o’clock. I was two ticks to the right of straight up. This is not a setting that really ever needs to be adjusted. I can see maybe a half tick tweaking over the life of the machine as parts wear.

I’ve also learned in my quest for knowledge that once you’re past the “start” ignition timing and are on the “run” portion of the magneto you’re supposed to be at 5/16” (or 1/4” depending on where you read this) from the END OF PISTON TRAVEL when you fire the plug. I always set it at 5/16” from the top of the sparkplug hole. Can’t wait to time this thing right.

Has anyone ever used a timing light to check timing on a Gravely? I’m going to break mine out and see what it looks like.
 

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I was two ticks to the right of straight up
That was how mine was set and I knew it was wrong.....I never check them but the po did liked to tinker so I went in!

The mags I opened up from the bucket were set at 5.1 to 5.5 from the left.

Has anyone ever used a timing light to check timing on a Gravely? I’m going to break mine out and see what it looks like.
Members have mentioned this but I have not read of it actually done..... Maybe a search of the forum would help.

RB in RI
 

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To use a timing light, you need to have some reference to actual TDC of the engine and some way to establish the actual degrees BTDC you want for the actual running timing.
 

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Discussion Starter #10
To use a timing light, you need to have some reference to actual TDC of the engine and some way to establish the actual degrees BTDC you want for the actual running timing.
Well, let me ask this then. Theres a timing mark on the mag itself that represents when the mag is firing, correct? Mine has two dots that line up over each other and a hash mark as timing marks. If either of these are the spark of the unit then I should be able to take my adjustable timing light and set it on 30 degrees and adjust the coupler until I get the strobe of the light hitting the timing mark on the mag............. and I've got it set at 30 degrees advance. Am I right about this?
 

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No good, it will always light up the mark regardless of where the actual timing is set. You need to view the relationship of where the spark is vs where the piston is. This is why the timing mark is on the crankshaft pulley in a car.
 

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No good, it will always light up the mark regardless of where the actual timing is set. You need to view the relationship of where the spark is vs where the piston is. This is why the timing mark is on the crankshaft pulley in a car.
nhgravely,
Are you saying that if the internal magneto plate show earlier by RI-GravelyMod was rotated that the mag would still fire whenever the marks align? I find this hard to believe else what does moving that plate do? It seems that rotating the plate that (i.e, adjusting the lag degrees) would certainly change the timing of when the spark is delivered... presumably... I think??? As simple as the magnetos are, I find them to be troubling. I, too, am curious about what parris001 was asking about validating the timing of the spark against the magneto position via a timing light and not that of the position of the piston. Subscribed as I am now curious about this!
 

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Discussion Starter #13
No good, it will always light up the mark regardless of where the actual timing is set. You need to view the relationship of where the spark is vs where the piston is. This is why the timing mark is on the crankshaft pulley in a car.
I have a timing light with a degree wheel on it. When I check timing on a car all I ever really need is a TDC mark on the balancer. I will dial in 30 degrees on my timing light and rev the engine and make sure that when all of the advance built into the distributor has been delivered my TDC mark lines up. This is usually higher up in the RPM range.

Since the Wico on a Gravely has no advance mechanisms built into in it becomes more like an ignition system on a drag car. They are locked into a setting usually somewhere around 30 degrees.

So if Gravely does provide me with a TDC marking which with a basic timing light will only show me when the cylinder is firing at TDC........... if mine takes crankshaft degrees into the equation I should be able to time mine at 30 degrees (or whatever I like) with this mark. Correct?
 

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Parris, the issue is that the T head engine doesn't have a TDC mark on the crank, or on the pulley attached to the crank. You have the timing marks on the mag itself, but since that's driven by an adjustable coupling, those marks are meaningless w/r/t the position of the piston.

You're trying to get the internal timing of the mag right after adjusting the impulse lag, correct? So really what you care about is making sure the mag (when not engaging the impulse) fires when the timing marks say it should. Once you've established that, you can time the mag to the engine using the usual methods for the T head.

It may be hard to check the internal timing with your light. You'd need something to spin the mag fast enough to disengage the impulse. It's likely easier to simply check when the points open, using an ohm-meter. Once you've confirmed that's happening at the correct time (when the mag's timing marks are lined up) you can stick the mag back on the engine and set it up so that same point happens at 5/32" BTDC. That should put your impulse release time right at TDC. If it doesn't, you need to adjust the impulse delay some more.
 

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Discussion Starter #15
I see where I was making my mistake.

The timing marks I have............ one a line and the other is two dots. What do the different marks denote?
 

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I see where I was making my mistake.

The timing marks I have............ one a line and the other is two dots. What do the different marks denote?
The line is where the mag fires when the impulse isn't engaged. That should be about 5/32" BTDC. The two dots are where it fires when the impulse is engaged. That should be at TDC or a touch after.
 

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Discussion Starter #18
The Wico magneto was one of those items I felt fairly squared away on and was confident in my abilities to tune. But WHOA, was I wrong. In the past I had glanced over the material and just moved on doing it the way I was confident it needed to be done.

I've done a deep dive since I made this original post. And actually READ the material. Gotta say my stuff has never started as good as it is now. Thanks for all the posters and the info. I really learned something this time.
 
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