H4 Magneto,Impulse coupling, Farmall H, No spark

This is my second post. I have a '42 farmall H. I bought in it '91 . I bought it to work a few hours a year mowing ,plowing ,general work and food plotting for deer at my place in the country. It's a work horse not a show horse. Well the truth is that it has been the most trouble free piece of equipment I own. I have not had to do anything but grease,oil and gas this gem. I grew up with B's A's and G's so tricycles never scared me. Any way this spring the H did not start. No spark. I knew nothing about magneto's except when my uncle had hold a wire,and I learned there was fire in that thing.(note to self) And they either worked or they did not. I had no idea there were points in there,and so I never gapped them. So by the time I figured that out and got to the points there was no gap. So I gapped them. Well it started but faded fast with weak spark, then quit after about 10 minutes of running on 3 cylinders. So I figure I'm going to replace points ,plugs ,rotor,etc. It's past due. . Have not done it yet but going to. So I'm seeing how to static time it on Utube, and I do not hear that sharp snap that should be happening. So that brings to where I am today. The impulse coupling. I can say for sure the springs are worn out or missing on one of the pawls. So I'm seeing $14.00 a piece for the springs on Ebay. Yikes! I'm a practical man. I won't pay $14.00 for a spring when there is a world of springs that cost a dollar that I might be able to get to work.( I'll post anything I can get to work. I know it's got to be out there) I'm in no great hurry. So this brings to my first question. Is the impulse coupling really necessary ,if you only use electric start? I figure I can static time it an ohm meter or light on TDC. I figure I'm going to need the ignition parts no matter what, so I'll deal with that later. Also I'm a bit fuzzy on checking the coil secondary. Is picture below right? If spark is still an issue after I buy the ignition parts ,I might buy a 12 volt coil and condenser and do a work around. Is the impulse coupling a must have? So if some could lend some guidance I'd be grateful.

Looks like a well piece that has not been taken care of. No wonder it doesent work well. There is no static timing and you dont go to 12v as a mag makes its own voltage. That mag will still fire it just doesent have and impulse to fire when first turned over but the rotor in the mag will still produce fire when turning as the impulse just happens when turning over slow. If all you want is a spring i have them but that area does ,ook awful rusty and maybe the dogs are worn also would you want the whole front assy i have that also and be glad to send as i dont need anymore stuff give me an adress and pay postage ect.

Thank you for your very generous offer. I tried to PM you but that does not seem to be working. Before I get too far down this road, if I can get function without the impulse coupling with an electric starter that works for me. I suspect the impulse coupling has not been working since I bought it in 91'. You answered my question about the impulse coupling, next I need to find out if my coil is any good. I need to find out how to check the secondary winding with an ohm meter. Thank you again. I changed my profile, so my email should come up.

Mike in IL.

You just mite want to pull the rotor and check the bearings also. Sometimes the rotor and fields get fusty so cleaning them up sure will improve spark since you already have the impulse off take the rest apart and clean and grease the bearings.

I believe the original H4 mag did not even have springs on the weights unless you are talking about the impulse spring. I would pull the rest of the impulse off and unless the weights are really really bad, you can square up the tips. I can see on the picture that the drive in dowel the weights contact to hold them until mechanism trips them is really worn badly. You can just drive that out and install it in a new position. You really do need the impulse to work for decent starting. It just gives the rotor a really fast spin at cranking speed to build a higher voltage and thus better spark. Once it starts the impulse has nothing to do with running of engine.

I'm going to pull it down further, as suggested. I suspect the coil is bad.. Thanks for the input.

mike

[size=18:61f0939342][/size:61f0939342][b:61f0939342]I got the chance to return to this project. I made a small puller and popped the plate off. It is on a tapered shaft with a woodruff key so a little pressure and a wack gets it done. I was very surprised by the size of the pawl spring. It is stainless steel as the manual says.Very small. I only had one. I'm going to post pics as I go along for the benefit of those who come down this road after me.





mike[/b:61f0939342]

[b:10dddb078d][size=18:10dddb078d][/size:10dddb078d]OK, I drove the pin out that acts as a pawl stop and reversed it. Now it appears as the end of the pawl is so worn it only makes very minimal contact with the pin, certainly not enough to load tension on the impulse spring the impulse spring. Will the pawls need to be replaced? And where would a person go find such parts?




Mike [/b:10dddb078d]

[b:710aaa1f21][size=18:710aaa1f21][/size:710aaa1f21] Would you please" safe email" about your offer of parts. I've tried to alter my profile to receive a PM, but it does not seem to be working.

Mike[/b:710aaa1f21]

(quoted from post at 16:30:25 08/28/15) You just mite want to pull the rotor and check the bearings also. Sometimes the rotor and fields get fusty so cleaning them up sure will improve spark since you already have the impulse off take the rest apart and clean and grease the bearings.

Click to expand...

Done. Rotor was pretty clean and seemed to well magnetized. Coil secondary checked out 10,500 ohms on meter. Condenser also metered as good. Ordered points , condenser ,rotor, cap.

Biggest hurdle so far is a functioning impulse coupling.

Mike