Belt keeps popping off.

The pic shows the tensioner spring is not hooked up to the frame at the correct spot and you are missing the belt guide at the smaller v pulley that keeps the belt on pulley.

Finally got around to where I could see the problem. Part #50 (anti-rotate bracket) was cracked and only being held together by a thread. It wasn't bent but actually cracked at the bend and became more of a hinge than a bracket. So it didn't fully break appart but flexed enough to allow the tranny to flex. After I removed the two large lug type wheels I could also see where the right side trans / axle mount part of the frame was also badly broken. I was moving fast in reverse backing into the woods so I could move a large snow bank and hit a tree stump hidden in several inches of snow. Had to completely dissasemble the whole back end AND also found the transmission case cracked as well. I can't believe the whole thing was being held together at all.

Sorry to not get back to the replies quicker. Spent a few days repairing and modifying the frame and am waiting for the new bracket and transmission to arrive.

Belt guide missing for the small pulley and the tensioner spring needs to be put in correct place at frame.

that small pulley MUST be aligned exactly with the other 2, as a matter fact you need to get down and look across all of them together and assure alignment. I bought an RZT for $800 once because the owner said it kept eating drive belts. I go it home and the engine pulley was off about 1/4 inch so I replaced it with NOS, it aligned perfectly and I sold it for $1800 a week later

k_damore said:

that small pulley MUST be aligned exactly with the other 2, as a matter fact you need to get down and look across all of them together and assure alignment. I bought an RZT for $800 once because the owner said it kept eating drive belts. I go it home and the engine pulley was off about 1/4 inch so I replaced it with NOS, it aligned perfectly and I sold it for $1800 a week later

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Where the belt rides on the deck pulleys is really important. I have had to modify the pulley height on newer mowers (less than 5 years old) to have the deck belt ride correctly and last.

k_damore said:

that small pulley MUST be aligned exactly with the other 2, as a matter fact you need to get down and look across all of them together and assure alignment. I bought an RZT for $800 once because the owner said it kept eating drive belts. I go it home and the engine pulley was off about 1/4 inch so I replaced it with NOS, it aligned perfectly and I sold it for $1800 a week later

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I've replaced the damaged anti-rotate bracket and new transmission and all the brackets holding the three pulleys. The two main pulleys were always in perfect alignment. But the smaller idiler pulley was always (before the damage occured) slightly tilted a couple degrees. I assembled with all new factory parts and that idler is still exactly tilted the same. I put all the old orignal brackets side by side and they are all absolutely exactly identical in every way. The old original larger two pulleys and their mounting hardware are all identical to my original. And the new idler and pulley are ALSO exactly identical to my originals.

And when all is assembled the idler pulley is tilted downward a couple degrees. Are you SURE that's not right? To me it look like it's designed to be this way.

Rich A said:

I've replaced the damaged anti-rotate bracket and new transmission and all the brackets holding the three pulleys. The two main pulleys were always in perfect alignment. But the smaller idiler pulley was always (before the damage occured) slightly tilted a couple degrees. I assembled with all new factory parts and that idler is still exactly tilted the same. I put all the old orignal brackets side by side and they are all absolutely exactly identical in every way. The old original larger two pulleys and their mounting hardware are all identical to my original. And the new idler and pulley are ALSO exactly identical to my originals.

And when all is assembled the idler pulley is tilted downward a couple degrees. Are you SURE that's not right? To me it look like it's designed to be this way.

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back to basics, as someone said before, there may be belt guides missing as the belt certainly looks too loose. And just because the new and old bracket for idler look the same if it doesn't line up even with the others then whatever it mounts to is damaged. The only place an idler is tilted a few degrees is on the deck to compensate for it being raised and lowered

I'll send a better picture .. the picture I originally posted, was taken when the thing was partially disassembled. Belt LOOKS loose cus spring(s) etc. were detached. When assembled everything is exactly as it was out of the box 12 years ago.

About 6 years ago I turned this thing into a snow plow only tractor. No mowing deck , no deck pulleys, belt or ANY mowing deck mechanics are on the frame. I've BEEN using it for 6 years for snow plowing and hauling a small trailer around 13 acres to haul cut up logs etc. It has run flawlessly and perfectly for that time UNTIL I backed over a stump. Only then did I have a problem with the belt popping off and it was only until a week ago when I finally completely tore everything apart did I see the damage which was hidden from view and was EXTENSIVE.

I can assure you that the idler pulley and it's bracket, ALWAYS had a slight downward tllt from the day I got it over 10 years ago. The damage caused recently was to the frame, transmission case and that part #50 what everyone calls the "anti-torgue bracket" which is called in the factory manual "Transmission Bracket Assembly". That bracket was almost completely broken in half and only being held together by a thread. AND because of that, it flexed when the tractor was put in gear, allowing the whole transmission to twist downward damaging the frame where the tranny axles mounts are, and mis-aligning the belt causing it to pop off.

Note, I could run the tractor at any speed in neutral and the belts pulleys etc. worked fine, properly aligned and no burning slippage or popping off. BUT as soon as I let the clutch out in either forward or reverse the whole transmission would flex because the transmssion bracket assembly was broken and the main drive belt would fly off. THIS is the cause of the belt flying off:


That part along with ALL the other "brackets" have been replaced and so far every NEW OEM replacement part is identical (to a few thousanths of an inch) in every way, bends, angles, thickness. AND yet that one idler pulley is still (just like it was out of the box when new) tilted downward a couple degrees.

Thanks for all the comments but I think the tolerance of the allignment of pulleys and belts on this tractor as shipped from the factory, while somewhat critical is not out of spec in my case. Maybe a 3 or more degree tilt will affect things but a 2 or less degree tilt is not a problem? So today I will fully re-assemble the whole thing with all the "new" OEM brackets, etc. and still see a 2 degree off-set of that idler and it will either work or not work. If not ... I'll be open to any other ideas. I really appreciate the suggestions and help. But this problem is obviously kinda un-common?

More pics to follow. I hope all this detail and info helps someone else in the future.