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Antique Gas Engine Discussion

FBM headless mag gear fit


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  #1  
Old 05-16-2005, 10:18:00 PM
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Question FBM headless mag gear fit

I have a FBM headless that has excessive lash between the mag gear and the cam gear. It needs to move down to bring the mesh into a more appropriate amount of lash. I see no adjustment as the bottom of the mag sits on the cast boss of the main block. Would it be appropriate to mill some material off the bottom of the mag???? Thanks Tom
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Old 05-16-2005, 10:34:44 PM
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Default Re: FBM headless mag gear fit

Tom,
Do you have the right gear on the mag? It should have DJ 142 embossed on the gear. Could the cam gear bearing be so worn that the gear has moved away from the magneto? How is the backlash between the crank and cam gears? Maybe the platform for the magneto was never milled right from the factory. Just a few thoughts.

Mike
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Old 05-16-2005, 10:35:24 PM
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Default Re: FBM headless mag gear fit

Tom,

I would say that it will be allright to mill the base of the mag because if you take off a little too much you can always shim it up with shim stock or hard paper to adjust the gear lash.

I just thought that you might try the poor mans milling machine if the base of the mag is not of the fall apart potmetal variety. When I was a Kid I used to mill the heads on Briggs and Stratton engines using the poor mans milling machine that my Dad showed me.

You just find a level concrete sidewalk, driveway or curb and start moving the surface that you need milled back and forth and all around. You will be suprised at how streight it will be if you vary the area on the concrete to make the milling surface random. I used to mill the heads then use a metal ruler to check the surface and it was always very straight.

Remember free advise is always worth what you pay for it.

I just got a mag gear for one of my headless engines. I still need an original igniter so that I can make the patterns to have some cast. I will either buy one or borrow one to measure to make a real pattern. Those cast using an original shrink considerably when they cool therefore the pattern has to be made oversise by formula to come out correctly. I need 2 and know of others who need them also. It seems that there are more headless Fairbanks Morse engines that need Igniters and mags that almost any other engine.

I am also going to try to make a low tension mag out of a perminant magnet motor/generator. If it works I will make brass end plates and fabricate a dummy horseshoe magnet to make it look somewhat original.

If anyone has done this please let me know.

Dick

Last edited by Dick Welty; 05-16-2005 at 11:08:54 PM.
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Old 05-19-2005, 09:45:35 PM
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Default Re: FBM headless mag gear fit

Thanks for the replies. I won't need to go to the street to mill the bottom of mag as I have a milling machine. No number on the gear. I guess I'lll cut the bottom off about 3/16" TJ
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Old 05-19-2005, 09:59:45 PM
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Default Re: FBM headless mag gear fit

Tom,
How many teeth are on the gear?

Mike
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Old 05-20-2005, 12:00:41 AM
Dick Welty Dick Welty is offline
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Default Re: FBM headless mag gear fit

Tom,

Mike is right if you don't have a gear with 30 teeth about 3 1/8th" in diameter you probably don't have the right gear.

The crank gear should have 60 teeth. This gives the mag 2 revolutions for each revolution of the crank.

If the cam gear dosn't have 30 teeth the impulse of voltage won't peak when the igniter trips. One tooth off will bring up the impulse at a different time each crank revolution.

The sumpter mag is marginal even when the impulse is right let alone when it is off.

Here is a picture of the correct mag gear for the Headless.

Dick
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Old 05-20-2005, 12:22:14 AM
Rudy Rudy is offline
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Default Re: FBM headless mag gear fit

Hi I beg to differ on the opinion of the Sumter low tension mags. I have a Headless , a 1919 1.5 H.p Z with a #14 Sumter and 2 - 3 h.p Zs with Sumter low tension mags and they all start really well on the mag. The biggest issue is that , like with any other low tension mag it has to be repaired right, not just patched together. Its like everything else ,you get what you pay for.
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Old 05-20-2005, 12:48:59 PM
Dick Welty Dick Welty is offline
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Default Re: FBM headless mag gear fit

Rudy,

My opinion is based solely on threads read on this forium. I admit that I have had no experience of my own. No one argues that anything with a potmetal base is problematic but that aside I think that you are probably right in that if they are properly rebuilt they undobtedly give good service.

My problem is that I need mags and Igniters for 2 otherwise complete and good Headless engines that I wish to restore. One has some paint left which I will probably cleanup with linseed oil and keep in that condition. The other is in rust condition and I think that I will put that one into factory or better condition just to illistrate to the public what can be done to these engines.

I know of others who have done the same and It seems to always draw the attention of the spectators at shows.

Dick
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