Replacing the Magneto on an 084

[Papee]

The mag gear is smaller than the gear on the cam. The mag spins twice for every time the cam gear turns one time so yes, the mag fires two times for every one turn of the cam.

No worries on bringing up an old thread, that is why we post them.

Was this engine running before this started? Have you had this motor started? I'm not sure how you are seeing a spark on the other cylinders, it could be because you have them out and not grounded. When you are saying 1-2 and 3-4 are you talking about the cylinder position or mag position?

[Doozit20]

Hello papee
Yes the motor was running when I got it and I have run it since then. I took all the plugs out but kept them in the wires and layed them on the block (carb did not have gas in it and no gas line was hooked up). Yes I am referring to cylinder number when I say 1-2-3-4. I only here a LOUD pop one per full turn of the rope start pulley. Again I was spinning it slow to check spark and the 1-2 were sparking great. Another note when I was checking this the motor was on the ground with no ground wire hooked anywhere that I can see. I do have a wire that the guy I got gge motor from hooked to the mag in two places that is used to kill the mag. When I spun the motor fast I got spark on the other two cylinders but not as strong. Could this be a points problem. I have the farebanks mag btw.
Thanks for the help Steve

[2006rubicon]

Hello papee
Yes the motor was running when I got it and I have run it since then. I took all the plugs out but kept them in the wires and layed them on the block (carb did not have gas in it and no gas line was hooked up). Yes I am referring to cylinder number when I say 1-2-3-4. I only here a LOUD pop one per full turn of the rope start pulley. Again I was spinning it slow to check spark and the 1-2 were sparking great. Another note when I was checking this the motor was on the ground with no ground wire hooked anywhere that I can see. I do have a wire that the guy I got gge motor from hooked to the mag in two places that is used to kill the mag. When I spun the motor fast I got spark on the other two cylinders but not as strong. Could this be a points problem. I have the farebanks mag btw.
Thanks for the help Steve

I think the loud "CLACK!" you hear when you rotate the mag over slow is the impulse coupling inside the mag, it winds up a little spring and then flips the armature around rapidly so you get a nice hot spark when you are trying to start up and the engine is turning slow. When the engine catches and the impulse is no longer needed, the spring is taken out of the picture by a centrifugal weight as the engine is spinning the armature fast enough to build a good strong spark by itself. This is probably why you can see spark on all plugs when you pull it fast with the rope, but not slow. sounds like either the impulse coupling is sticking and not working for cyls 3 and 4, or a points/cap/rotor could be dirty or worn, you should definitely be seeing two sparks per revolution, even turning it slow. I'd pull the cap/rotor and have a look see, it might just need a good scrubbing!

[Doozit20]

Rubicon
Ok so I should hear that loud clack twice per rope start rotation? When that pop is heard is when I saw the spark. The order of fire is 1423??? So if that's correct either my points or condener or both it bad for my 3 and 4 cylinder. Assuming that's how it works. Or could it be the impulse impulse spring thing. I'm unfamiliar with mags and really don't want to take it off my motor. Can I check this on the motor or do I have to remove it from the engine.

[2006rubicon]

yes, two clacks per rotation. You can check the cap/rotor with the mag on the engine, after unscrewing the plug wires, there are two tiny screws that hold the cover of the mag on, after you take that off, you will see the cap and rotor. They work the same as a car, just smaller. You can get caps and rotors pretty easily, I think Saturn surplus has a pile. Check their Ebay store. As far as the impulse, I wouldn't sweat it if the engine runs good. It just means you will have to pull the start cord a little faster is all!

[Doozit20]

Ok I'll check that whenever it stops raining here and I get freed up. When I cranked the motor it ran a little rough but I don't have exhaust on it yet (I'm still building my boat) and I didn't tighten the plugs up tight after I took them out so I know that didn't help. I've got around 120-125 psi on all cylinders so I get good compression. I think I have a valve hanging open on a cylinder as well because when I hold my hand over it and rotate the motor slowly it will push the air out but then it will suck a little back in so that's something I have to look into as well. But that's the nature of these things right. For tinkering. Thanks for all the help so far. I'll post what I find after I take the mag apart.
Steve

[Doozit20]

Can someone please tell me the model number on the slick mags. Is it 4220?
Thanks Steve

[Papee]

The 4220 is the correct model number for the slick mag fitting the 084.