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Tecumseh Points Push Pin


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#1 robert_p43 OFFLINE  

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Posted October 13, 2012 - 07:25 AM

The motor is Tecumseh 143.579032 HH100
Sears suburban 10
That pin is stuck good. Well, not good. LOL I put some of my homemade "rust-bust" on it 2 days ago. Today, I removed the points thinking I might try to give it a tap but noticed a little chunk missing. It is not the whole end but just a corner like someone had already tried to get it unstuck. I guess I need to take the route that MH81 suggested. (split the case and work my way to it from the inside) I am afraid that the pin may be ruined though. Is this something that I could have made up in a machine shop? Or better yet, I have a brother that restores and repairs old clocks. He has tools and stuff to make tiny-tiny little pins. and gears and stuff that are inside clocks. I am not sure he would want to do this but it's worth asking. Does anyone know the specs on this part? Length, diameter, are the ends squared off or supposed to be round? What material would work? steel? brass?
I put most of this on my tractor post but then thought, other brands have this motor and the same points set-up so I am posting the questions here.
Thank You,
Robert

#2 MH81 ONLINE  

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Posted October 13, 2012 - 07:29 AM

I have a brand new one here. I will take measurements tonight and a couple of pics.

The pin itself is some kind of fiber composite. Be very careful to use something softer than the cam lobe to reduce the chance of wear.
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#3 Bruce Dorsi OFFLINE  

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Posted October 13, 2012 - 08:56 AM

As MH81 has said, the hardness of the material needs to be taken into consideration.

Another thing to consider is the possible expansion of the material when exposed to heat & oil, as well as the diametric clearance required.

If the clearance is too small, the new pin may expand and seize in the bore. ....If there is too much clearance, oil getting onto the points will be a problem.
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#4 johndeereelfman OFFLINE  

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Posted October 13, 2012 - 10:34 AM

Get rid of the old figerglass points rod, and cut yourself a new rod using a 16 penny nail. Cut the nail to length, and round the edges slightly to get rid of the sharpness. I have used this method in all of my tecumseh motors and never had a problem. The nail is hard enough to do the job but also soft enough to give when it needs to.

The old fiberglass rods start to wear after a while and eventually absorb oil, causing them to swell and stick. If you can, use a drill bit smaller than the rod size, and drill out the center of the rod. Do not use a drill, just turn is by hand. After you have most of the old rod removed, clean out the remaining fragments as best you can with a toothpick or dentist pick if you have one. When everything is cleaned out of the hole, drain the oil and put in fresh.
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#5 robert_p43 OFFLINE  

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Posted October 13, 2012 - 11:59 AM

I have a brand new one here. I will take measurements tonight and a couple of pics.

The pin itself is some kind of fiber composite. Be very careful to use something softer than the cam lobe to reduce the chance of wear.

A brand new one? Where on earth would you find that? LOL I figured if I could get one made, I would go ahead and have a few made. It may not be the only one I'll ever need. Plus, it could turn into a source for others.

#6 robert_p43 OFFLINE  

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Posted October 13, 2012 - 12:07 PM

As MH81 has said, the hardness of the material needs to be taken into consideration.

Another thing to consider is the possible expansion of the material when exposed to heat & oil, as well as the diametric clearance required.

If the clearance is too small, the new pin may expand and seize in the bore. ....If there is too much clearance, oil getting onto the points will be a problem.

This is probably why they didn't use metal in the first place. It has to fit fairly tight and if it expands, it would only damage the pin, which was probably readily available at the time.

#7 MH81 ONLINE  

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Posted October 13, 2012 - 06:35 PM

I had to run up to the farmstead for a while. Be later on tonight before I can get the measurements. (pin is back down at the house) Sorry for the delay.

#8 MH81 ONLINE  

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Posted October 13, 2012 - 09:00 PM

Ok, pin in hand. Calipers not in drawer. Either I, or someone else used them and didn't put them back.

Drill index for diameter, 1/8". Actually, pretty tight but 9/64 is loose. I remember reading in a tecumseh manual somewhere that you may need to fine sand the new pin before installation for a proper fit... So this kinda makes sense.
Tape measure for length, 3/4" spot on.

This one has never been installed. I can see the factory saw marks in the ends.

#9 robert_p43 OFFLINE  

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Posted October 13, 2012 - 09:44 PM

Thank you again. I hope that I will be able to pass on this much help someday.
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#10 MH81 ONLINE  

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Posted October 13, 2012 - 09:49 PM

Just pay it forward, and if you get a decent line on suitable pin material, let us know where you found it.

#11 robert_p43 OFFLINE  

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Posted October 26, 2012 - 07:08 PM

This is what my older brother told me. He is making mine as he repairs clocks and has material and tools to sometimes make little clock parts. (parts for a 200 year old clock aren't always something that can be found. Kinds like Tecumseh points push rods) He said he had made 2 so far. One out of soft brass and one from hard brass. Both crept away from the tooling in his lathe and he ended up with a thousandth taper. I didn't think that bad but he didn't like it. Then he remembered that when he worked at Bryants as a machinist, he had made some grinder parts using a material called, "delran." He said he has a 1/2 inch rod in with clock stuff somplace and will try to find it. He said, it wears well, won't change with the temperatures of a small engine at all. To dense to suck up oil, and good friction too. I tried to google it and have come up with delrin, my guess is it's the same stuff.
I told him that a 9/64" drill bit fits in the hole in the casting so he is going to machine a couple of thousandths smaller.
If this works well, I surely will let you all know as if it is Delrin, it is readily available. They just don't have that small a rod available, so it would have to be machined.
Maybe I should have just cut off the nail. I might be riding the tractor right now instead of looking at it. LOL!
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#12 MH81 ONLINE  

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Posted October 26, 2012 - 07:15 PM

Glad the engine is on the road to recovery.

If the stuff isn't expensive, he may find a small niche market with them.




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