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Discussion Starter #1 (Edited)
MTD Model 31A-611D129



OK, so I'm doing this swap from a Tecumseh 2 pulley to a single pulley Briggs. I have EVERYTHING worked out, then I figured out, and sure enough I over looked something.


The second pulley that drives the wheels, spins in the opposite direction. I can tell the guy reverse is forward and forward is reverse, but that's too easy. I'm looking at this part called the shift rod assembly. See attached picture. This is the part that I'm looking at.



I am thinking that the shift rod assembly for the two pulley system is simply a mirror image of one for the one pulley system. So before I start cutting and welding, can I just buy the one for the single shaft output and will it be just a mirror image of this one?



I want to make this work, because someone told me I couldn't, and I'm stubborn that way.



Suggestions?
 

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I need to do this also on a 10/29 MTD if I can't find a replacement Tecumseh 8-10hp engine. Keep us all informed, with step by step PICS! Please.

My understanding you need to do a complete reverse of everything underneath to the other side? If all you need to do is re-weld the shift rod assembly, Great!
 

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Discussion Starter #3
I need to do this also on a 10/29 MTD if I can't find a replacement Tecumseh 8-10hp engine. Keep us all informed, with step by step PICS! Please.

My understanding you need to do a complete reverse of everything underneath to the other side? If all you need to do is re-weld the shift rod assembly, Great!

I'm trying to figure it out without destroying the shift rod assembly, since they are NLA. If they were still available, I'd already have cut it. If you have an extra one laying around, I'll give it a shot in the interest of science. It makes perfect sense if I mirror image the shift rod, it should just work, but I have to sit down and draw it out on paper.



I can reverse everything underneath, that's "easy" way out. :grin::grin:


Like I said, when someone tells me I can't do something, I make a point of doing just that. So let me know if you, or anyone who reads this, may have one. I'll buy it if you're not a pig about it. Don't ask for $100 it's not gonna happen.
 

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Discussion Starter #4
So I called MTD and ordered a new part. I'm going to rip it out, and get it welded. I have a firend that does all my welding, one thing I never learned was welding.



I'm going to take this out, do the mirror image, and hope it works. I don't see how it won't except that 1 would be the fastest, and 5 would be the slowest, maybe. On paper it looks fine, but I'm like Wyle E. Coyte. Lots of plans, and lots of fails. But sometimes, things just work. We'll see.
 

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Discussion Starter #5
Hey JLawrance, I think I have it figured out, and it seems very simple. Smack yourself in the forehead simple.


I pulled out the shift assembly rod. The pin that sits in the carrier is just pressed in, and not very tightly. I knocked it out with a hammer, turned it around, and put it back in, swinging the arm 180 degrees.



I may have to re-drill the hole at the end of the bar, that holds the shifter rod, not sure yet, but it doesn't look that way, and theoretically, if I'm going a complete 180 I shouldn't have to, anything more or less I may.



I'm not sure what it will do to the fastest gear, since it is so close to the center. But everything else lands where it should, at least on the correct side of the center of the drive pulley.


Now, nothing is done till it's done, but it LOOKS like it should just work. Once I realized how easily that pin came out, the rest was simple.
 

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This part can be made with a flat piece of steel, rod, jig saw, and of course a welder.
 

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Discussion Starter #8
This part can be made with a flat piece of steel, rod, jig saw, and of course a welder.

Easily. Don't even need rod, just use the old one, this way you know the length is right, the holes are in the right place, and the diameter is correct.
 

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Reversing the rod seems to work for this guy on YouTube but I don't know him, I know you, waiting to hear back from you. Isn't this a summer project?
 

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Discussion Starter #11
Reversing the rod seems to work for this guy on YouTube but I don't know him, I know you, waiting to hear back from you. Isn't this a summer project?

This project started with a start up landscaper. He asked me to look at one of those older craftsman/Murry machines. The gearbox was shot, it needed a lot of work, far more than the machine was worth. But it had a good 6.5 HP briggs.


I got this MTD for free from a guy whose tennents left it there. The body is really nice, but the engine was a 5 HP Tecumseh. It was left out in the weather with no sparkplug in the head, and no spark plug wire. So I asked him if he wanted that Briggs on a better machine. I took the tires off the Murry/Craftsman because they were better, wider tires, but I had to use the old bushings on the new machine to take up space on the axle.



He doesn't need it, he bought a brand new Toro PowerMax. This is a backup machine for him. I work on it at my liesure. I have nothing to do today. I'm waiting for two carbs to come so I can get two machines out the door. I've had a real rough week, getting in and out a ton of machines, so I'm just taking it slow today, and I decieded to go stare at this machine. Look at it, get intimate with it. So I stared for a while, did a few drawings on my computer with arrows noting direction and such, and I finally pulled the trigger to go take it apart and see what is up.



The rest is here in this thread. I'm waiting for my new cell phone to come, my 30 day old one crapped out, as soon as that comes, I'm going to run the carrier and pin over to a friend, get it welded, and pick up the right size belt, and see how it works. Probably be done Thursday. I only have about 2 hours in it, and $70. So it's not all that much. I told him a few hundred to do the swap, so I'm not losing. PLUS I like doing this stuff, especially because someone said it couldn't be done.
 

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I didn't have time to watch the videos ........



Did they address the fact that the second shaft turns at half the speed of the crankshaft??

I personally have not undertaken this swap yet, but it is on my to do list as it has been a thorn in many engine swap projects. I could be mistaken about half speed, but know it turns opposite of the crankshaft rotation.
 

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Discussion Starter #13
I didn't have time to watch the videos ........



Did they address the fact that the second shaft turns at half the speed of the crankshaft??

I personally have not undertaken this swap yet, but it is on my to do list as it has been a thorn in many engine swap projects. I could be mistaken about half speed, but know it turns opposite of the crankshaft rotation.

Yes, the speed will be off, but the location of the rubber drive wheel will be different too. So we'll see what it is. L
 

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I only watched the MTD track machine video. He had started with a 3” pulley and found it to be ridiculously fast. He dropped down to a 2” pulley and stated it was much more reasonable.... although he did not test drive it in the video.
Why re-invent the wheel??? But he provided enough info for me to give it a shot if I find time.
GLuck, Jay
 

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Discussion Starter #15
I only watched the MTD track machine video. He had started with a 3” pulley and found it to be ridiculously fast. He dropped down to a 2” pulley and stated it was much more reasonable.... although he did not test drive it in the video.
Why re-invent the wheel??? But he provided enough info for me to give it a shot if I find time.
GLuck, Jay

I have the smallest pully I can get on the front, about 1 inch. So in theory, it should be twice as fast, if the rubber wheel lands in the same spots on the left, as it does on the right. What ever it is, it is, only use the bottom two for plowing anyway.
 

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Discussion Starter #16
OK, more investigation. Tomorrow, if I have time, I'm going to go to my welder's shop. Here's what I'm going to do.


1. cut the plate off the rod


2. weld a new rod to it, or flip the existing rod 180 degress. Basically just weld a new rod to the other side of the plate.



So you ask why do we need a new rod?



Because when the carrier guide is moved , the screw holes won't necessarily line up with the control bar, handle that changes makes the speed change. It's really hard to get the screw holes lined up perfectly, so drilling new ones is the best option. I'll just put a new bar on it, mark, and drill a new hole through the rod. Easier than trying to get the new plate in line with existing holes.



Not really that hard a project at all, just needs to be thought through. Takes a lot of staring at the open bottom of the machine.


Also, consider that the carrier guide as I call it (thing with the pin) swings in an arc. This is why there is play on the carrier where the pin sits. When the carrier guide swings, the carrier needs to have some play.



It will work if you simply swing the carrier 90 degrees, however, I feel a mirror image of the original is the best way to go. I don't know that if during operation the carrier will stay in place at 90 degrees. But I do know it will if it's a mirror image.
 

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Discussion Starter #17 (Edited)
OK, you old timer experienced guys are probably laughing at me, knowing there's no easy/effective way to do this. I tried a bunch of appraches with the carrier, but the problem starts before the carrier, at the shift lever. THAT is what needs to be reveresed too. The new machines have Reverse on the left, this machine has it on the right. I'm going to look into turning the shift lever guide plate upside down, cutting the ends off, and welding them so they fit the handle bars.
 
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