Re: Won't run after sitting in the rain :-(

Thu Apr 25, 2013 11:01 am


Just to make sure it is clear, Donny's method would work, but since there is a proper tool available, I would echo Rick's suggestion to acquire the new type of impulse puller tool if you can. Better safe than sorry. Also if you have someone close with parts -- even better. You might be able to acquire a complete magneto for reasonable coil.

Oh.. and I am not nagging.. well trying not to ... but after raisin 5 kids it is almost inbred :big smile:

Re: Won't run after sitting in the rain :-(

Thu Apr 25, 2013 9:38 pm

Does anyone know the diameter and thread pitch for the inside of that coupler plate? My dad (who has done machining since he could walk) took one look at that picture of the tool and said "I could make one of those!".

Re: Won't run after sitting in the rain :-(

Fri Apr 26, 2013 5:12 am

It is a very odd pitch, that much I remember. But I don't trust my memory enough to quote it. There is possibly a post on here with it, but a quick search didn't turn up anything for me. I do remember that the only place I could find that currently has such a size/pitch combination is in plumbing fittings. DO NOT hold me to this, until someone else can correct me or confirm my guess, but I have a vague memory of 9/16" x 28 pitch......

Re: Won't run after sitting in the rain :-(

Fri Apr 26, 2013 10:20 am

What is this tool called? I'm trying to search for it, but I don't know what to call it. "farmall cub impulse coupler puller" isn't coming up with much. Where did you find that picture?

Re: Won't run after sitting in the rain :-(

Fri Apr 26, 2013 10:51 am

Ah ha! I think I have the info. The 9/16" info was close enough (someone else on this site had also said 9/16 but didn't know the threads).

Anyways, searching "farmall cub impulse coupler puller 9/16" brought me this site: ... &th=349509
Which says the threads are 24.

So, for any future person reading this forum: Looks like it's a 9/16 x 24. Sounds like it's a tough bolt to find. McMaster doesn't even have them. I'll respond further if we get one made, and if it works.

Starting to feel like I'm seeing daylight at the end of this tunnel! Thanks for all the help!

Re: Won't run after sitting in the rain :-(

Fri Apr 26, 2013 10:56 am

Further examination reveals that those instructions are for an H4 mag, so hopefully the dimensions aren't different.

Re: Won't run after sitting in the rain :-(

Sat Apr 27, 2013 11:59 am


I searched the archives Magneto Impulse Puller and got some good hits ..

This one I think answers the question nicely:

Subject: magneto impulse puller

John *.?-!.* cub owner wrote:a few people have expressed interest in a puller for removing the impulse on the J4 magnetos recently. A retired machinist friend of mine that has his own shop made a couple for me, and said if i could give him an approximate number, he would make up some more. Cost on mine was $35, but if he gets request for several it will probably be cheaper. The same tool works for J4 and H4 magnetos, maybe others also, but I don't know about that . If you are interested in one let me know. When I know how many I can give accurate price.,

I posted this here rather than For Sale forum, due to the fact I am doing this for a favor, not for a profit.



And this one :idea:

Subject: J4 Magneto

Rick Spivey wrote:The impulse puller is a 9/16' - 28 thread, IF I REMEMBER CORRECTLY.....

Your Dad should be able to make one up now. Would like to see pics etc., of it when it gets done.

Also, does anyone have some good pics of Earl's Impulse Puller?

Re: Won't run after sitting in the rain :-(

Sat Apr 27, 2013 12:32 pm

Here is mine that Mike (farmertan) made.
mag impulse puller 004.JPG
You do not have the required permissions to view the files attached to this post.

Re: Won't run after sitting in the rain :-(

Sat Apr 27, 2013 12:42 pm

Not a great picture, but here it is:

9/16 - 24 is the size and thread. Fortunately my dad had access to a lathe at his work and could make that thread pitch for me. It worked like a charm.

Unfortunately - once I got it open there are no pawls underneath. I'm guessing that maybe because it has a 12v conversion on it that the starter gets it going fast enough that the impulse coupler wasn't needed. Was the impulse coupler a safety thing for hand-cranking? I don't know, I'm grasping at straws here. It ran FINE before the rain. I could idle it down all the way to the bottom of the throttle and it would go nice and smooth.

Ultimately, I would love to get the pawls in place, but it appears that for right now its not my root issue.

Fortunately my neighbor is letting me borrow his Massey (am I allowed to say that word here?), so I'm able to get yard work done - but this is driving me nuts. It ran for a little while (maybe 2 minutes) again today (I re-gaped the points and plugs) but it was running really rough (but no surging) - and now it wont start back up.

I'm stumped. Not sure how to continue checking the time without the impulse coupler.

Re: Won't run after sitting in the rain :-(

Sun Apr 28, 2013 7:51 pm

Just back from my weekend. I couldn't remember if it was a 28 pitch, or 24, glad you guys figured it out. Now, just to repeat some basics, you have a magneto with external coil, and no impulse coupling. Just some reminders, even though the magneto is ACTING like a distributor, the points still need to be gapped at 0.013" like a magneto, and NOT 0.020" like a distributor. Without the impulse coupling, it could be more dangerous to hand crank, since the impulse retards the spark for cranking, However, if you are on the starter, the safety is not an issue. The only other issue would be hard starting. I think, since the real issues started with the rain, you should confirm that the "kill" post is not grounded to the magneto frame, like Charles related earlier. Other rain issues include moisture in distributor cap, and maybe moisture inside your mag, since the coil cover looks a little suspect.I would insure all is dry, reset the points. You can time it with an ohm meter, looking for when the points open and lose contact with one another. So rotate the mag body away from the engine block until you lose continuity through the points, and you should be plenty close enough. Report back on what happens after that.

Re: Won't run after sitting in the rain :-(

Sun Apr 28, 2013 8:33 pm

After I found out about the impulsing coupler pawl missing I will DEFINITELY not be hand cranking it anymore. I like all my fingers right where they are.

I will check the gap on the breaker points because I think I have them set to .020. I had found another forum thread where some guys said .013, and some said .020 (with the hybrid system I have) so I picked one. I have been checking that my points are actually breaking using an ohm meter, and that all appears to be working. Moisture COULD have been an issue, but its been opened, swabbed, and had enough time to dry now that I don't think that could be it. Also while my dad was making the puller, he machined a nice, tight-fitting cap for where the mag coil used to be, so that should help me in the future, and it looks nicer.

Without the impulse coupler I can't static time it using the usual process, since it's permanently in the advanced state without the pawls, so I'm hoping that the lines I made are getting me these. I have been over it a bunch of times so I don't think I'm missing anything obvious. I read somewhere that the magneto usually runs at 13 degrees advanced, and that the first timing mark is at 16 degrees advanced, and I know that the spark comes just a little past the first mark - so I think that all sounds about right.

I got it to fire up again yesterday on the first try, and it ran for a bit (really rough again, though) and then died after a few minutes and wouldn't start back up again. The odd thing is even that after it ran I pulled the #1 plug (to verify at what time it was sparking) and I had no spark - just after I had it running! That has me more than a little confused. However, I could get spark at the coil (with a plug wire and plug attached directly to the coil), and with my ohm meter I can tell that my points are still opening. The distributor cap is new, and looks bone dry. A friend just loaned me an extra coil of his, so I'll try that and see if that makes a difference.

I WILL figure this out, and when I do I will be the happiest man alive! Thanks for all the help!

Re: Won't run after sitting in the rain :-(

Mon Apr 29, 2013 5:31 am

At this point, I also would begin to suspect the coil. The timing might make hard starts, or poor running, but not running for five minutes before shutting down. That sounds more like a coil breaking down, which may or may not have anything to do with the rain event.Good Luck!

Re: Won't run after sitting in the rain :-(

Mon Apr 29, 2013 5:14 pm

I swapped the coil and I still have the same issue: I seem to be getting good spark from the coil, but little or no spark after the distributor cap. With it connected at the coil I even tried opening the plug gap up to a rather large gap and I still had what looked to be strong spark, but still not good at the actual plugs.

I went to order a rotor at Steiner - but holy cow they are $40! I was not expecting that. Not sure what else to check, though. The distributor, plug wires, and cap are all new (also from Steiner).

Re: Won't run after sitting in the rain :-(

Mon Apr 29, 2013 7:57 pm

So I assume you are checking the coil by pulling the wire out of the distributor cap, and holding it close to a ground such as the engine block. With new wires (all 5, right?) and new cap, I am left to question again if the rotor is timed correctly to the pinion, and if the pinion/rotor has too much slop. So the pinion fits only one way due to the flat side in the bore/on the shaft. Then the line on the pinion must be lined up to the line on the rotor. Lastly, the rotor gear teeth and pinion gear teeth should not have too much slop, or else it is like retarding the spark. Please confirm again that this is all correct, and sorry for asking you to recheck things you've already answered before. But I am also coming to a dead end quickly if we don't find something here. Opening the point gap only changes the timing, it won't change the spark quality. The points will spark when continuity is lost no matter how far you open them.

Re: Won't run after sitting in the rain :-(

Mon Apr 29, 2013 8:27 pm

Rick - I really appreciate the specifics, and reiterations. This is my first project of this type, so I'm SURE there are many things I'm not doing quite right.

When I check the spark at the coil, I'm pulling out a spark plug and the plug wire, attaching the plug wire directly to the coil, and then pushing the plug up against something grounded (somewhere with no paint, or the outside of another plug). I have not checked every wire. They are pretty new (3 months or so, maybe) so I haven't doubted them.

The pinon and rotor appear to be in good condition. I haven't seen another (good or bad) to compare to, but there doesn't appear to be any visible signs of wear. The copper conductor on the top of the rotor is a little discolored, but not much (however, I have no idea what constitutes a "bad rotor" as I've never seen one). As far as slop, I checked today and the rotor can maybe wiggle 1/8" or less. I have the two lines lined up, and when I set the engine to #1 TDC I have the rotor pointed directly to the #1 tower. This also hasn't changed since it ran last (Saturday morning).

Is there any way to test a rotor?

I was seeing a little spark today at the plug, but it didn't seem nearly as bright as when I had it connected directly to the coil. Directly from the coil I could even open the plug gap up quite a ways and I would still get a solid crisp spark - but when I reconnected the coil to the cap and the plugs back in the spark was much thinner, dimmer, and it seemed to me irregular.

I was planning on ordering new points, a condenser, and rotor today (because it couldn't hurt at this point) - but the rotor price stopped me in my tracks.

What symptoms does a bad condenser have, anyway?

I feel really bad with how long this has gone on. I feel like I've been hogging the top of the forum for a long time :-/.