48 Cub Magneto Timing Help?!

[farmergiffIV]

I am considering having an extra magneto on hand does anyone else carry a spare and fix them as you go a long?

IMHO it's a lot less trouble and easier to maintain (not to mention the reduced cost of parts) to convert to a battery ignition system. When the battery ignition system became available it was offered as an upgrade for the older (magneto) systems. You can probably buy one by advertising on "THE VINE, Classified" forum. Just be sure you get ALL the parts. The points, condenser and distributor cap are the same and interchangable but the rotor and coil is not.

I actually have a battery ignition system, but I have been working on getting it working smoothly, last winter I drove the tractor in to the shop to try and adjust the governor rockshaft..... Here is where I am at now, I've replaced the head gasket and reassembled everything and ever since I haven't gotten her to start up.

[Glen]

Hi,
I gave you info for a magneto on the previous page, which a 1948 Cub would have originally had. If it has a Battery Ignition unit, do not disconnect any wires from the unit when trying to make the engine run. The wire on the side of a Battery Ignition unit has to be connected.
You didn't tell us before that it has a Battery Ignition unit.
A picture of what it is would be helpful.
The ignition points and condenser have to be good for it to run, if after replacing those the spark is still weak, the coil could be weak and need replacing. The Battery Ignition unit uses the same points and condenser as a magneto, the listing for new ones is on the previous page.
Here are pages from the Cub owner's manual showing how to replace the points and condenser.

http://farmallcub.com/rudi_cub/www.clea ... e%2041.jpg

http://farmallcub.com/rudi_cub/www.clea ... e%2042.jpg

[staninlowerAL]

Several posts indicate and reference a magneto and its components. Now in today's post you're referencing a battery ignition unit. So which is it? It's like comparing apples and oranges, both are fruit but that's about all that is similar. Agree with Glen, a picture of what you have would help. Reread your entire post, If you do have a magneto, just make sure when you are rotating the engine with it installed that the fire has someplace to discharge to, otherwise you risk permanent and irrepparable damage to the mag coil.

[farmergiffIV]

Hi,
I gave you info for a magneto on the previous page, which a 1948 Cub would have originally had. If it has a Battery Ignition unit, do not disconnect any wires from the unit when trying to make the engine run. The wire on the side of a Battery Ignition unit has to be connected.
You didn't tell us before that it has a Battery Ignition unit.
A picture of what it is would be helpful.
The ignition points and condenser have to be good for it to run, if after replacing those the spark is still weak, the coil could be weak and need replacing. The Battery Ignition unit uses the same points and condenser as a magneto, the listing for new ones is on the previous page.
Here are pages from the Cub owner's manual showing how to replace the points and condenser.

http://farmallcub.com/rudi_cub/www.clea ... e%2041.jpg

http://farmallcub.com/rudi_cub/www.clea ... e%2042.jpg

Sorry to be frank. Since last post, I got a rebuilt mag that was tested on a tractor earlier on the tractor, the old one I am going to replace condenser.

When I pull the plug from the middle plug on the mag and hold it near the engine the spark looks good and bright after I hand crank.

I have electric start- I will leave the kill switch on, I havn't had any good luck using the electric start yet, since the battery runs out quick since it wont start after a few tries I am back on the charger... and I reckon I don't have the generator motor yet properly running.

[farmergiffIV]

Several posts indicate and reference a magneto and its components. Now in today's post you're referencing a battery ignition unit. So which is it? It's like comparing apples and oranges, both are fruit but that's about all that is similar. Agree with Glen, a picture of what you have would help. Reread your entire post, If you do have a magneto, just make sure when you are rotating the engine with it installed that the fire has someplace to discharge to, otherwise you risk permanent and irrepparable damage to the mag coil.

My battery ignition unit isn't working so I hand crank to start at this time. I just wanted to clarify since I thought I never mentioned before that the battery ignition does exist, but since I cant get the tractor to start I am hand cranking until I get the initial part figured out otherwise I kill the battery often.

I am certain the mag works like I mentioned in the other post, now I think its the carb not set properly, If not then it must be something else. When hand cranking it felt like it almost caught, then the carb started flooding and I figure I blew it from there. That happened a couple times over and over, I am using a dummi gas tank with no sediment bowl, I just dought its the fuel supply to the carb- I am assuming the carb is not set properly since I am using a new original style carb to try and start, clean new fuel too.

[tmays]

Not sure, but by battery ignition I think he is referring to the starter/charging system, and has a mag on the tractor.

Make life easier for yourself and either charge battery fully with a battery charger or get a new battery. If you're having problems with the tractor starting, then a hand crank can be very frustrating(and tiring)

[farmergiffIV]

Reread your entire post, If you do have a magneto, just make sure when you are rotating the engine with it installed that the fire has someplace to discharge to, otherwise you risk permanent and irrepparable damage to the mag coil.

I'll post some pics soon, to be clear its a magneto with a electric starting motor, I am not sure how this is confusing as this is the only cub I have

I also think I may have hurt my magneto coil as you posted this earlier and I think I cranked the engine over with mag engaged but coil wires disconnected.. Oh, well I replaced the old mag and I have a new coil that needs installed.

Not sure, but by battery ignition I think he is referring to the starter/charging system, and has a mag on the tractor.

Make life easier for yourself and either charge battery fully with a battery charger or get a new battery. If you're having problems with the tractor starting, then a hand crank can be very frustrating(and tiring)

I got a new battery a month ago and this darn thing aint start'n! and so the battery keeps dying on me

[staninlowerAL]

Sorry to be frank. Since last post, I got a rebuilt mag that was tested on a tractor earlier on the tractor, the old one I am going to replace condenser.

When I pull the plug from the middle plug on the mag and hold it near the engine the spark looks good and bright after I hand crank. THIS TELLS ME THE MAGNETO IS WORKING.

I have electric start- I will leave the kill switch on, EXPLAIN WHAT YOU MEAN BY THIS STATEMENT, IS THE SWITCH PULLED OUT OR PUSHED IN? I havn't had any good luck using the electric start yet, since the battery runs out quick since it wont start after a few tries I am back on the charger... and I reckon I don't have the generator motor yet properly running.

Just to be clear: a magneto works totally independent of the battery and its related components. You can start and run the tractor with a properly installed and adjusted magneto, no electric starter motor or battery is needed. The battery/gen/VR is only there to recharge the battery that supplies current to the starter motor (as well as aux equipt, lights, etc) If you haven't done so, I suggest download a copy of GSS 1012 and thoroughly familiarize yourself with the magneto and battery ignition information in this service manual.

[Glen]

Hi,
Here are pics, the 1st is a magneto, from TM Tractor, the 2nd is a Battery Ignition unit.

[Rick Spivey]

I think I am following g your post correctly, so here goes. On your first magneto, in addition to (possibly) the coil and condenser, you MUST repair the insulating post for the kill switch wire. TM Tractor sells the parts needed, which include a metal stud, and plastic insulators. The new ones don't look like the older ones, which were thick bakelite. That thick one is what you found crumbled inside your magneto. I don't think electrical tape will be a long term fix. The electricity will take the path of least resistance, and leak at this point.
As for the second magneto, I would suggest you find a time with a really clear head, and go through the engine timing routing again. At no pony should you say, "but I already checked that". Instead, really walk through it like it was your first time. Trust me, it is very easy to be 180 degrees out of time.
And lastly, one of your earlier posts made it sound like you had a battery ignition unit on hand, which replaced the magneto in cubs built in later years. Those require the battery to be fairly good in order to produce the spark, whereas the magneto produces its own spark, no battery required. It sounded like you had that unit ready to be put in the cub once you got it running again. This was where the confusion started, and I may still be confused in my interpretation. So if you are running with the magneto (attempting to), let's not use this post to talk about battery ignition.
Since the second magneto seemed to give a good spark, then we will assume it would deliver that to the cub, which leaves engine timing, or as suggested, maybe yet another problem altogether. It is helpful to sort out one at a time, so insure you are getting a good spark at the right time, and then we can all move to carburetor. Hope this helps.

[farmergiffIV]

Hey All,

so after spending much time. I've found, I have spark and the engine is properly timed. I have only 25-30 psi compression on average for all cylinders.

I am going to pull the engine off and replace engine block at this time.

[staninlowerAL]

Hey All, so after spending much time. I've found, I have spark and the engine is properly timed. I have only 25-30 psi compression on average for all cylinders. I am going to pull the engine off and replace engine block at this time.

That's pretty low compression. Not sure what you mean about "replace engine block". There are several things that can contribute to low compression. Worn rings, valves not seating properly due to wear or lack of maintenance, etc. I suggest you try to diagnose the problem before starting to replace parts.

[farmergiffIV]

Hey All, so after spending much time. I've found, I have spark and the engine is properly timed. I have only 25-30 psi compression on average for all cylinders. I am going to pull the engine off and replace engine block at this time.

That's pretty low compression. Not sure what you mean about "replace engine block". There are several things that can contribute to low compression. Worn rings, valves not seating properly due to wear or lack of maintenance, etc. I suggest you try to diagnose the problem before starting to replace parts.

Yes, I've decided to have my mechanic friend bring over his special tool that he says can diagnose whether its the piston, valve or... I do want to consider taking the whole block off and getting it rebuilt though as I'd like this tractor reliable. It always seemed to be low on power when hauling implements and it appeared to overheat often making me wonder if the engine is worn too much and needs finer adjustment. But perhaps just the valves need adjusted that would be an easy fix.