Magneto...Firing to late...Makes no sense...

Raner

Member
I went to the ranch today to reinstall the magneto on my 1949 farmall H.
If you have been seeing by posts, The main thing I found was the rotor and drive gear were out of time.
I set them where there suppose to be for a right rotating magneto.
I bring number one piston to TDC, Look at the engine gear that drives the mag,
The pig ears are at 3 and 9 clock hand position. Were they are suppose to be.
I make sure the mag just fired #1 and the pig ears on it are at 3 and 9 also...
I install the mag, then rotate it all the way towards the engine.
I turn the engine over and bring it back to TDC on #1 piston.
I rotate the mag away from the engine towards me, I rotate it all the way out
till I run out of adjustment and the mag will not snap to fire number on cylinder.
If I leave the mag all the way pull out and rotate the engine on it's normal rotation
I have to rotate it another 1.5 inches and it will fire #1...
Makes no sense... #1 piston is on TDC (The piston is all the way up) and the TDC mark
on the pulley is dead on the pointer.
The piston is where it's suppose to be, The mark on the pully is were it's suppose to be, and
the mag drive gear is where it's suppose to be, and I installed the mag making sure it just
fired #1.
What the heck am I missing... I can't see why the mag will not fire #1 when I pull out
towards me on the second go round...
Here is a picture to help you see what I am talking about, it's pretty well self explanitory...
https://drive.google.com/file/d/0B5BRN9d1ovVHUFJVUXJ2RlJwV1k/view?usp=sharing
Thanks for any help guys & gals...
 
A piston that is on TDC can be on TDC on the exhaust stroke. (one possibility) The crankshaft turns twice for every rotor rotation. Jim
 
Hi Jim... I made sure #1 piston was on compression stroke heading to TDC the 20 times I checked it... LOL...
 
I'm thinking you have to leave the #1 piston below tdc, rotate the mag in the retard position enough to install it. then bring the piston to tdc, and advance the mag till it fires. Firing the mag before you put it in throws it off, that's why the extra 1.5 inches to coil and snap the impulse.
 
Well Cole... Makes sense to me... I give it a shot...
My way sure the heck ain't working...LOL
Thanks Cole...
 
I always put engine near top dead center, rotate mag in opposite direction of rotation until the rotor is near number one and lugs align with drive. Install and push mag toward engine, turn engine to top dead or a couple degrees after and then pull mag out toward you until snaps. If you cannot make impulse snap doing that and have to turn an inch and half past top, you are off a cog on the drive. No other way about it as the impulse cannot be changed even if magneto was internally out of time on rotor end. Mark where lugs are before pulling drive for reference and I believe 3 o'clock is too far when top dead center.
 
Thanks Pete... Hey you said off a COG... Do you mean a tooth off from mag drive gear on the engine?
If so, Does the mag drive gear run of a main engine gear or is there one gear in-between the engine drive gear and the mag lug gear...
If I remember right on my uncle's B Farmall the engine side of the mag lugs were at 2 and 8 at TDC...
So were the mag lugs...
 
Your rotor is off. Take the mag back out make a mark on the body where 31 tower is. now turn the magover and look when the rotor stops it should point at that position. I have 7 mags and thats the way i set them put them in the tractor and it will start on the money. Its easier to instal the mag rite after it fires as you can turn the rotor to get the slot lined up where the mag drives easier. You can leave the cap off and turn the engine over and see if the rotor stops at the mark you made.thenturnengineand watch it snap. Have you cleaned the impulse with some solvent and blow it out this cleans the impulse good.
 
Thanks Gene...
If the rotor is off from the marks I made on the mag body for #1 and #3 cap towers.
Are you saying to turn the rotor and make sure it points to marks I made on the body...
In other words time the rotor to the marks and forget about the
timing on the drive gear to the rotor gear...
 
The rotor timing will not change when the impulse snaps. Is this the same mag that was on this engine? The gears driving the mag off the camshaft are not timed right for a mag. It will still work with a distributor. Set the rotor timing on the C mark & leave it.
 
Thanks Teddy... Yes this mag came off this tractor...
I bought is a couple of years ago...
I looked at the front of the engine and everything looks like it's never been disturbed not even the pulley...
 
If the lugs are at 3 & 9 and they should be at 2 & 8 what is going to take for me to set them to the correct position...
 
Raner, I have been fighting the same problem for about a week. Got my 41 M finally running today. the plate behind the impulse spring on mine was broken, I bought a used one at junkyard, couldn't make it work, went back and got another one.
Fought with it for 3 days, impulse was snapping at tdc, but rotor was about 30 degrees to left of no. 1 tower. not enough rotatation on mag body to make up for it. Today I moved plug wires one tower ccw, rotated mag to center of adjustment. I hit the starter and she fired right up. Doesn't make sense, but it worked. The rotor drive gears are set up correct with the R lined up on the chamfered tooth/cog. Different from original set up tho as the no. 1 plug wire is in no. 4 tower now.

Dick ND
 
The rotor is out of time but i run into that problem from time to time just had one other day first clue was when i noticed the wires werent in their correct places the rotor was off 90deg and a little off time lined up the gears so it fired on #1 tower and alas engine fired rite up.
 
dont change that gear or you will be realy messed up there are timing marks on that gear and they need to line up with the cam gear or valve timing could then be messed up. I am talking about the gear that drives the mag
 
Thank you all for taking the time to help me with my problem...
But here is the deal. I know my engine gear drive lugs are at
3 & 9 position when the # 1 piston in compression stroke is at
TDC and the pulley mark is at TDC.
So if there is no way to time the mag to the drive gear, No
mater what I do I'll will always be late on timing because of
where the mag snaps to fire the cylinders.( Piston is on it's way down probably and inch or so)
The only way I see to get the timing correct is with a distributor.
I have never seen the guts of one but I'll bet it's got four cam lobs for the points to open. If I'm right then the position of the lugs don't matter because they are now just drive lugs there is no impulse to time anymore. So the rotating adjustment on the distributor housing should have enough to time the firing of the cylinders BTC as it should be...
 
Did it ever run right? I have run into this before as there are other engines that use the H4 mag. But the lugs are in a different place on the drive.
 
It isn't to tough to remove the governor and turn the governor/mag drive shaft/gear a couple of teeth top towards the engine block.
 
Tyhe governor on an H is not on the same side as the mag. It is the distributor drive housing. (not a flame) Jim
 
The impulse is what he is trying to get timed properly. You could throw the other end of the magneto away and still time the impulse correctly. You just need to pull the drive off and move the gear a cog. If this tractor had a battery ignition on it, you can put the drive on any way you want because the distributor of the battery ignition unit can be installed any place you want it due to the gears in dist drive. Really, this is a rather simple deal. Forget about the 3&9 stuff and put the gear to where impulse is tripping at tdc or slightly after, never before. And will add, the mag has just two lobes and reduction is in the rotor drive end.
 
Thanks, Jim, I neglected to get deep enough into the thread to realize he was dealing with something other than an A-B-C, etc..
 
Let me start this last post on the mag timing problem. With this!
I want to thank each and everyone of you that took the time to
help me out on my post...
Ok Guys I got it...The whole works is timed to a tee.
I know this procedure will work on a H and maybe a M don't know on other models.
Since my lugs were at 3 & 9 when the impulse was snapping the timing was way restarted.
So I had to fix this problem first.
This morning I took off to the ranch early got there at daybreak.
I looked at the tractor and decided to take a peak to see how the mag drive gear was driven.
I got # 1 piston on compression stroke and put it at TDC. The mag drive gear lugs were sitting at 3 & 9 but I already new that.
Then I pulled off the four bolts on the gear housing and found the mag drive gear is an independent gear that is driven by one to the tractors main gears.
When I saw this, I told myself this is going to be a piece of cake.
So I moved the gear one tooth so that the lugs were at 2 and 8, And bolted the housing back on. Since I had already timed the the rotor gear to the drive gear. I knew they were fine.
I got a pair of vice grips and turned the engine backwards till the lugs on the mag engine drive gear were at 3 & 9 then I grabbed the mag from my tailgate and turned the mag backwards till I was pointing to # 1 on the cap and continued moving it backwards till the impulse lugs were at 3 & 9, I installed the mag
and rotated it all the way in towards the engine.Then I brought the engine back to TDC. Then I pulled
on the mag about 1/2 an inch and it snapped. Locked it down put my cap back on and hit the starter and the tractor fired right up.
So in shot the mags impulse timing can't be changed on the mag however the drive gear can be moved to get the mag impulse to snap in different places. So the adjustment is in the drive gear to change the mags timing of the impulse. So in a sense the mag can be timed... Thanks again guys...
 
Well, I guess that I what I was trying to say all along. If you had that front cover off , you would find you could align the timing marks on the gears but that is difficult to do with cover on so you just go by getting it close and seeing where impulse trips and go from there to change it a cog or two.
 
So your gear hat drives he mag is off a tooth that makes the cam a little out of time shouldnt make too much of a problem. You never know on a well used tractor what previous owner had done but it sure can make headaches. You would need to pull the front cover to get the dots lined up but for now glad you got it running.
 
Gene...
When you pull the mag drive gear housing the gear that drives
the mag the one with the lugs comes right out.
The gear for the cam I guess is the gear that drives the mag gear.
The mag gear is an in-depended gear only for the mag.
When you move the mag gear it does not effect the engine crank or cam gear.
When you pull the mag gear housing you just grab the mag gear and it comes right out. When it's out you can see the teeth of the gear that drives it. I would not have moved the mag gear a tooth but when I looked to see how it mounted I could see that moving it was not going to effect the timing of the crank or cam because to get to them you would have to disassemble the front of the engine... :D :D :D
 
Now that I got the timing of the engine and the mag to fire correctly...
I decided to give the H a complete ignition system over hall.
I'm replacing all the wiring on the primary and secondary circuits.
Yesterday I went and got this parts:
12 volt coil (For External Resistor)
Ballast Resistor
Cap, Rotor, Points, Condenser (For H4 Mag)
Spark Plug Wires (Copper Center Sold Wire)
3116 Auto-lite Spark plugs
I got everything all put together and ready to be installed.
With all new terminal connections (Soldered and insulated with shrink tube)
Below is a link for the diagram of my set up.
If you want to download a copy to your computer, Just click on the down arrow symbol on the right top of the diagram window...
https://drive.google.com/file/d/0B5BRN9d1ovVHZ2IzM2VfYnpRMGc/view?usp=sharing
 
I've been posting on this forum since I bought my H.
Getting help from you all on problems I had mostly
Carburetor and engine performance. I would like to tell you
all that every single problem I've ever encountered are history...
H is running and pulling better than ever.
The biggest implement I have is a 24 dish disc.
I disced a small section around the cabin.
Made several passes till I had the disc digging all the
way to the axles.
I was in fourth gear at half throttle the engine ran like a champ and not a burp one.
Here is a link for a 30 second video to the H starting and running...
https://drive.google.com/open?id=0B5BRN9d1ovVHQVl1dGhST1JwckU
 

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