spark and mag question.

[Thackery]

I've been working on my freebie cub on and off this winter.
Never have been able to start.
I was reading over old posts, and now I'm wondering.
If there is a problem inside the magneto, like something sheared or otherwise broken, would I still get spark?
I do get spark although it is not real strong.
I've been just trying to get this cub started to see if it is worth continueing on. And if the clutch, hyd, etc. work, then I will try to restore.
I have already followed Chauvin's list, and fixed a few problems along the way. I am now going to start over on the list to try and confirm everything.
In the Chauvin information it says that you find TDC and then move the mag away from the engine until it clicks? Is this click when the spring tension tabs finally slip past the lobes on the casing? Or is it something else. I can make my mag slip past the lobes when I have it in my hand but I don't think that I hear this when I turn the mag away from the engine.
I'm charging my battery now to see if I get better spark and I can give starting another try.

Thanks for everyones help.

Doug

[Donny M]

Thackery,

Charging the battery will not effect the spark of the mag.
When you place #1 at TDC install the mag (with the rotor pointing at #1on the cap) with the top of the coil cover against the engine block. Now turn the engine over one rev back to TDC. Rotate the coil cover away from the engine until you hear it click. The engine should be timed at that point.

[beaconlight]

Just because a mag is timed does not mean it is making a sufficiently strong spark. A mag will make a hotter spark than a distributer.
That clicking being talked about is an internal spring causing a short swift movement inside the mag. If you remember your highschool physics the more turns of wire and the faster the movement of a magnetic field in relation to the turns the higher the voltage. Un fortunately a mag builds so high a voltage that unless it is hooked up to something the voltage may damage its internal coil. This weakens the spark for the future. A mag in good shape should create a bright blue sharp spark that will easily jump 1/2 inch. It will make a good loud crack too. If you are the thing the spark goes through, you will know it.

Bill

[Mag Man]

If you would like that Mag rebuilt or looked at by a slightly used professional you can send it my way. I will admit if the trip is weak I dont have any good used ones at this point but alot of times things can be tweaked slightly to get better results. You may also have a weak coil and as I exspressed a few days ago the chavuns mag page has the wrong point gap for a mag. It was put in for a distributor.
a mag point gap is 13 thousands.
JON

[Thackery]

13 thousandths? My mag has been converted to run off 12v the actual mag coil is not doing the work. How does that affect all of these variables? I have a gap of 20 at the points. I did not think that the battery would effect my spark, but it does help it turn over. I know that my starter is in bad shape from my repeated cranking.

As a side note: I have been using spray starter fluid to try and get some firing instead of gas. Mostly because I have the gas tank off and I don't really like the idea of a bunch of gas around while I'm testing for spark all the time. I also wanted to rule out the carb with the spray fluid and then go with gas. (Trying to cut my possible problems in half).

Mag Man, I was going to check the spring area of my mag but really did not see an easy way to break loose the center bolt/nut what the heck do you hang onto to get leverage.

Thanks, Doug

[Eugene]

Essentially you have a battery operated ignition. Low battery voltage will effect spark.

Doug, I just don't know what to tell you. If this were my tractor I would clean up all of the connections - check for corrosion inside the distributor cap and in the spark plug towers. Check the voltage coming into the coil. Dress the points and set back to .013.

I have the feeling that you have a bad external coil and or condensor breaking down.

Have you conducted a compression test?

Eugene

[Bigdog]

I think Eugene has nailed it with his suggestions. The mag distributor was designed to operate with a .013" point gap. Anything other than that will affect timing and efficiency. And since you are operating with an external coil, battery voltage will affect spark.

[Mag Man]

Well the book says to put a nail through the hole in the side and take it off. LOL. But I have an impact gun that I can set for torque that I use to take them on and off. Off is no problem just hold the outside of the bell but on you need to be real carefull that it just gets snuged and not over tightened. You will not find much that you can do under that cover without a special puller to pull the reast of the trip and if you bang on it the clips usally fall off under neath and alow the trip to fall apart. J4s trip pulling are the worst I have found sometimes even with the puller they can be a real bear.
JON

[Thackery]

I will reset the gap to 13 and get a good battery charged up.
I don't think I'll try to take apart the mag, sounds like a Mag Man job.
I have not tried a compression test. All cylinders will blow my thumb up when turned over with the starter. I had already corrected a stuck exhaust valve on #3. At least that takes me back to 4 out of 4 instead of 3 out of 4.

Thanks, Doug

[Bigdog]

The "not real strong" spark is probably a major contributor to non-starting. Sometimes the voltage drop that occurs during cranking the enging over with the starter significantly reduces the available energy to generate ignition spark. Re-check all connections including grounds to see if that will improve spark. Also re-gapping the points and making sure they are clean will help. If you still have problems, see if you can get someone to help you pull-start the tractor.

[Eugene]

If the engine will blow your thumb off the spark plug hole, you have enough compression for the engine to run.

My recommendations. Have MagMan rebuild your magneto as a magneto. While you are waiting on the magneto clean up the fuel system - fuel tank, sediment bowl, fuel line, carburator. Clean the air cleaner. Clean the crankcase ventilation tube and orfice.

Auxillery fuel tank. Do you have a fuel tank from an old lawn mower? I use a portable outboard motor fuel tank.

Sounds like you headed in the right direction.

Eugene

[Thackery]

I had a neighbor tractor buddy come over and pull my cub down our road, and actually got it to fire. I was trying to pop start it in 3rd and once I actually gained on the truck. I couldn't try much because I have the tractor stripped down, without coolant or oil. But anyway it looks like my big problems with starting are behind me. I need to rebuild my starter and get a new battery. Right now it turns over so slowly that I think that is my big problem with getting started.

Thanks for everyones help so far.

Does anyone know of a forum like this for Allis Chalmers. Thats what my neighbor needs to work on.

[Eugene]

I'd put oil in the engine before I tried to start the tractor. I would change out all of the fluids before I tried the engine. I would also put in plain water before I tried to start the tractor - drain every night in freezing weather.

http://www.allischalmers.com/forum/forum_list.asp

Eugene

[Mag Man]

I couldn't try much because I have the tractor stripped down, without coolant or oil.



I really hope you made a mistake on that post and there is oil in that motor. That would be a good reason for it to turn over slow. Also a 6 volt with mag does not have to turn over only at cranking speed.
JON

[Bigdog]

Thackery - I hope you mean you have no oil in the tranny and rear end and not the engine.