• If you like antique engines, vintage tractors or old iron, please register and join us. When registering, please provide your CITY and STATE in your location!

Fairbanks Morse Headless Ignitor Rebuild

Jim Gorter

Registered
I need to replace the points on a headless ignitor. How do you remove the moveable electrode? book says there is a set screw, but I cannot find one. There is a taper pin on the pawl that i think needs to come out. also what to use to attach the points? Thanks for any help. Jim.
 

GlenK

Subscriber
Last Subscription Date
12/21/2015
Re: FBM headless ignitor rebuild

Jim, If I remember correctly, you take out the bolt on the clamp that adjusts the spring , and the moveable electrode slides out . I'm not 100% sure but what I understand about replacing points , you file the back side of them and drive them out with a punch . Then push the new ones in and peen them on the back to hold them in . I hope this helps ! Glen
 

Jim Gorter

Registered
Re: FBM headless ignitor rebuild

Thanks Glen, My ignitor does not have a clamp for the spring. It has a torsion spring around the pawl and a tension spring on the outside of the shaft support casting. One end of the torsion spring is held with a taper pin. I cant find any screw to hold the fixed end of the pawl on the shaft. Jim.
 

GlenK

Subscriber
Last Subscription Date
12/21/2015
Re: FBM headless ignitor rebuild

I keep forgetting there are two styles of igniters on the headless and always assume it's like mine , sorry about that . I have not seen the newer style yet . Glen
 

Junkologist

Subscriber
Last Subscription Date
12/28/2019
Re: FBM headless ignitor rebuild

Jim,
You have the later style ignitor. Just drive the taper pin out and "unscrew" the conical shaped spring off the end of the shaft and it should slide right out of the ignitor casting.
Remove the old points and install the new ones like Glen said and you should be back in business.:)
 

Jim Gorter

Registered
Re: FBM headless ignitor rebuild

Thanks for the info. My moveable point is brazed onto the arm and the stationary electrode has just the round rod with no point contact and no flat spot and hole to rivet in a new point. Possible to braze or silver solder a new contact on the round electrode pin?
My other concern is after attaching the new contact, I will have to reset the gap and I dont have the set screw on the pawl to readjust. Maybe just bend the arm a bit to reset the gap? Thanks, Jim.
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
Re: FBM headless ignitor rebuild

Jim:

As long as the linkage will allow the ignitor points to open and close in time, there is no adjustment of the gap.

In other words, the gap don't make no never mind.

Take care - Elden:wave:
http://www.oldengine.org/members/durand
 

GlenK

Subscriber
Last Subscription Date
12/21/2015
Re: FBM headless ignitor rebuild

The more I learn about these engines , It seems they did something different on every one of them . Do you think the points where brazed at the factory or was it done later? Glen
 

Junkologist

Subscriber
Last Subscription Date
12/28/2019
Re: FBM headless ignitor rebuild

Sounds like Jim's ignitor may have been reworked in the past. I have two headless Z's with each style ignitor. Both have peened over points on both electrodes and are original to the best of my knowledge.
 

Jim Gorter

Registered
I believe that Junkologist is correct. My engine has serial #255288. The moveable electrode has been repaired and the contact point brazed in. The stationary electrode is just a round rod with no flat spot to attach a contact. Once I add the thickness of the contact, the gap will be gone. The points stay open until the trip finger closes them just before it trips. The points fire but the spark is variable. I figure with bigger contact points the arc will be stronger.
This is the same engine that had a 32 tooth gear on the mag. So I dont doubt that some other areas may have been monkeyed with. Thanks for the help, Jim.
 

Junkologist

Subscriber
Last Subscription Date
12/28/2019
Jim,
You should be fine with your round rod stationary electrode. There were original ignitors for other makes of engines made that way. The nice thing about those is if you get a worn spot, all you have to do is rotate it to get a new spot.:)
 

GlenK

Subscriber
Last Subscription Date
12/21/2015
Jim does your igniter have a threaded hole on the outside of the moveable electrode and another one on the body of the igniter where you can put a ground wire ? My headless had intermitting spark and I installed a ground wire and it made a world of difference . Glen
 

Junkologist

Subscriber
Last Subscription Date
12/28/2019
Glen,
Jim has the later ignitor without the ground wire. His has a conical spring on the outside end of the moveable electrode which accomplishes the same thing as the ground wire.:)
 

Jim Gorter

Registered
Guys, My ignitor has the conical spring on the outside for sealing the moveable electrode, but it has a threaded hole and a screw in the same electrode on the outer end.
My contacts only open up about 1/16 inch. This is what worried me about readjusting the gap after installing a new contact. Jim.
 

Junkologist

Subscriber
Last Subscription Date
12/28/2019
Jim,
Sounds to me like someone has made a completely new moveable electrode for your ignitor at some point. The original electrode would have had a sort of mushroom head at the outer end to retain the conical spring. That's why I said you had to "unscrew" the spring to remove it. Sounds like yours just has a screw in the end to retain the spring.:shrug:
The earlier ignitors had a screw in the end of the shaft to attach a ground wire. The other end of the ground wire attached to the ignitor casting just above and to the left of the shaft when looking at it straight on. This gave the shaft a positive ground. The same thing being accomplished by the conical spring on the later ones, besides helping it seal too.
 

Jim Gorter

Registered
Actually, My ignitor has the mushroom tip, but the arm to the contact has been repaired in the past. I just cant seem to get consistant good spark. May be the moveable shaft is a bit sloppy and not getting consistant contact with the round rod. Possible that the tension spring is putting too much drag on the moveable electrode? Thanks for all the help, Jim.
 
Top