843 assessement

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bluffcam

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Got this 843 with no history, auction machine not running with U-joint flopping about. Got it home pushed into shop and felt around and found the shaft broke on the hydrostatic pump. Got started tearing it down and plan on pulling the pumps and putting in a new shaft. Noticed a bulge at the rear of the chaincase so pulled the inspection cover, One chain has some damage, RH side. In pulling hoses off pumps haven't noticed any metal. I'll see more when i pull the pump apart. Any hints/experience on what to check on drivetrain (chains, motors, and drive gearboxes). I was planning on draining chaincase and pulling rectangular inspection cover on gearbox. I did ask a pump seller off ebay about the shaft and he said it was rare to have the shaft break. Got me wondering what caused it to snap. I have parts and service manuals looking for source of parts---dealers only?? and an operating manual Can't get back to work on it for a week or so, studying manuals until i get back to wrenching. thanks Tom go to "http://www.mtaonline.net/~bluffcam/843/843.htm" for pictures
 

Tazza

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The chain wear looks odd. Is the chain stretched causing it to rub on the bottom of the chain case at all? If its stretched too much you may need to replace the chain. I have never seen a pump shaft break but i guess its a potential point that it could break. There is a fair amount of load on this shaft as it converts all the engines power to hydrostatic power. Hopefully nothing has let go inside the pump causing it to lock up and snap.
All i can recommend is draining the chain case and mopping it out with rags. I'd drain all the oil you can from the hydrostatic system and replacing the filter. When you get the pump out and if you confirm the shaft just broke i see no reason for concern on metal particles. But if you do have metal bits you really should clean the hoses and i;d recommend pulling the motors down and re-sealing them so you can clean out any bits that got inside.
 

bluffcam

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The chain wear looks odd. Is the chain stretched causing it to rub on the bottom of the chain case at all? If its stretched too much you may need to replace the chain. I have never seen a pump shaft break but i guess its a potential point that it could break. There is a fair amount of load on this shaft as it converts all the engines power to hydrostatic power. Hopefully nothing has let go inside the pump causing it to lock up and snap.
All i can recommend is draining the chain case and mopping it out with rags. I'd drain all the oil you can from the hydrostatic system and replacing the filter. When you get the pump out and if you confirm the shaft just broke i see no reason for concern on metal particles. But if you do have metal bits you really should clean the hoses and i;d recommend pulling the motors down and re-sealing them so you can clean out any bits that got inside.
I'll be digging further into it in a week, Is there any tricks to starting after the hoses have been pulled off and reconnected to get the air out of the system?
 

Tazza

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I'll be digging further into it in a week, Is there any tricks to starting after the hoses have been pulled off and reconnected to get the air out of the system?
I have never worked on an 843 but i have done a fair amount on 743's.
Getting air out is not a problem, the system will self bleed. Just work it and it will do the rest.
Just keep it all clean clean clean. Plug any open hoses or ports to keep any junk out. I personally squirt any joints i am going to un-do with de-greaser (diesel or kero works well too) then blow down with air to keep as much dirt away as possible before cracking the joint.
Just take your time and mark hoses as you go.
 

Tazza

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I have never worked on an 843 but i have done a fair amount on 743's.
Getting air out is not a problem, the system will self bleed. Just work it and it will do the rest.
Just keep it all clean clean clean. Plug any open hoses or ports to keep any junk out. I personally squirt any joints i am going to un-do with de-greaser (diesel or kero works well too) then blow down with air to keep as much dirt away as possible before cracking the joint.
Just take your time and mark hoses as you go.
One more thing, LOTS of oil when you re-assemble the pump. I always clean my parts with kero and blow them down with compressed air then apply generous amounts of oil when re-assembling. Lube all O rings before installing them to prevent pinching.
 

bluffcam

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well I got the pumps off and tore down. good news is nothing cratered and pumped metal through the system. bad news is it looks like the u-joint flopped around hit the bolt and knocked off one of the ears on the pump. I was thinking i would need a new housing/pump but after getting it all out and looking at the flimsy plate it was hooked to I wonder if there isn't much torque and stress there and 3 bolts would be OK(keeps pumps lined up). Other question is on the shoes, they do have some scratches and the book says “check for scratches” Other than the scratches the guts look good. If anyone has some experience/advice take a look at the pictures at:
http://www.mtaonline.net/~bluffcam/843/843.htm
 

Tazza

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well I got the pumps off and tore down. good news is nothing cratered and pumped metal through the system. bad news is it looks like the u-joint flopped around hit the bolt and knocked off one of the ears on the pump. I was thinking i would need a new housing/pump but after getting it all out and looking at the flimsy plate it was hooked to I wonder if there isn't much torque and stress there and 3 bolts would be OK(keeps pumps lined up). Other question is on the shoes, they do have some scratches and the book says “check for scratches” Other than the scratches the guts look good. If anyone has some experience/advice take a look at the pictures at:
http://www.mtaonline.net/~bluffcam/843/843.htm
There is a fair amount of torque put on the pump but i can't see that 3 bolts wouldn't hold it, but thats a decision you will need to make.
As for the shoes, scratches mean nothing, the shies run on the yoke and do pretty well nothing. Check the shoes for sharp edges, if they are sharp wipe the edges with wet and dry sand paper. When the are sharp that means you have wear and metal will start to flake off the sides, thats usually what makes them sharp. You don't want this metal coming loose and floating around the system.
The part you need to check wear on is the other end of the rotating group that runs on the swash plate. Grooves here effect performance. You can use a sheet of glass and wet and dry sand paper to make them smooth again. I think sterlclan did this before, i did a quick search but couldn't find his post on it. It took a bit of work but cost next to nothing, just a gasket set and some sand paper.
 

bluffcam

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Oct 6, 2007
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There is a fair amount of torque put on the pump but i can't see that 3 bolts wouldn't hold it, but thats a decision you will need to make.
As for the shoes, scratches mean nothing, the shies run on the yoke and do pretty well nothing. Check the shoes for sharp edges, if they are sharp wipe the edges with wet and dry sand paper. When the are sharp that means you have wear and metal will start to flake off the sides, thats usually what makes them sharp. You don't want this metal coming loose and floating around the system.
The part you need to check wear on is the other end of the rotating group that runs on the swash plate. Grooves here effect performance. You can use a sheet of glass and wet and dry sand paper to make them smooth again. I think sterlclan did this before, i did a quick search but couldn't find his post on it. It took a bit of work but cost next to nothing, just a gasket set and some sand paper.
thanks for the lesson in hydrostatic pumps, no sharp edges on shoes and other end looks good. this machine won' win any beauty contests so i believe i'll put it back together when i get the new shaft and see how it does. good info
 
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