mott 72 flail mower problems

jonsstihl · Jun 12, 2016

I recently got my hands on a mott 72 flail mower for a great deal (free) but the cutter shaft is seized. I though I just needed cutter shaft bearings but it seems to have other issues. I looked online and am going to contact montage for any info about a parts catalog. this appears to be an older model with the small round roller but there doesn't seem to be any set screws on the the inside of the cutter shaft bearings and there are no set screws on the outside.

I got the cutter shaft to turn by loosening the bolt holding the drive pulley on the cutter shaft. I was hoping to let it turn at idle for a bit to loosen up the bearings but when I looked a little closer at the pulleys they appear to be out of alignment and at some point in its life (before I got it) the cutter shaft pulley was too far in and rubbing on the bolt holding the roller bracket. Now the cutter shaft pulley is too far out, and when I torque the bolt holding it on it seizes back up on me.

If anyone has any info on how to get the cutter shaft off I would appreciate it and I would really like to have some kind of parts catalog to determine if the pulleys are original and what the spacing should be.

jonsstihl · Jun 15, 2016

I managed to get the cuttershaft pulley off last night and figured out what was going on. the pulley side bearing on the cuttershaft is seized and the shaft was turning inside the bearing when the pulley bolt was untorqued but when I torqued the bolt it would seize up. hopefully a new cuttershaft bearing will be the right width and will bring my pulleys back into alignment.

Steave · Jun 15, 2016

Never worked on one of these so can't help but I was interested non the less. It don't appear to be any adjusting for the pulley on the cuttershaft. Once you get your new bearing in you'll know then.

You say there's no set screws on the bearings. The bearing itself may not be replaceable not sure. It may come as a one piece deal just unbolt the old and bolt up the new but something has to hold the shaft in place? I'm just guessing here and hope somebody that knows something will chime in. I'd like to know how it works also. If it don't line up after the new bearing is installed maybe the top pulley can come out to meet it. The idler for the tensioner is a little more forgiving about a perfect alignment. Good luck with it.

jonsstihl · Jun 19, 2016

Got the cutter shaft off and figured out what was wrong. the last guy who changed the cutter shaft bearing put it in inside out so the grease zerk was not greasing the groove with the holes in it. so the bearing was running without grease. and it ended up almost a 1/4 inch too far out. a new bearing properly installed and right side out should solve all of my issues. One thing I noticed is that the bearing housing is not the same on the pulley side as the non pulley side.

the pulley side has a shoulder in the recess to seat the bearing against and the non pulley side has no shoulder and mine is currently a loose fit with the bearing so it can adjust to the length of the cutter shaft. I think having the bearing properly seated will correct my pulley alignment problem.

Steave · Jun 19, 2016

I noticed they looked different but wasn't sure if the housing was different but with the same bearing or what was going on there. Glad you got it figured out sometimes something like that is hard to see that it has been changed and then all of sudden it hits you. It's another good thing you were doing the work yourself instead of in a shop with them charging $45 - $75 / hr labor. You got a deal in that tool maybe I'll get that lucky someday. I'd probably go ahead and buy it even though I have two rotary cutters already.

Those belt pulleys need to be as perfect inline as possible. I also have a Landpride finish mower and the pulleys must be inline because I've never replaced the belt. Bought it used and been cutting for years with it on the same belt. Son-in-law has a cheaper brand (not sure which one) and has to replace the belt at least once a year.

Steave · Jun 23, 2016

jonsstihl said:
Got the cutter shaft off and figured out what was wrong. the last guy who changed the cutter shaft bearing put it in inside out so the grease zerk was not greasing the groove with the holes in it. so the bearing was running without grease. and it ended up almost a 1/4 inch too far out. a new bearing properly installed and right side out should solve all of my issues. One thing I noticed is that the bearing housing is not the same on the pulley side as the non pulley side.

the pulley side has a shoulder in the recess to seat the bearing against and the non pulley side has no shoulder and mine is currently a loose fit with the bearing so it can adjust to the length of the cutter shaft. I think having the bearing properly seated will correct my pulley alignment problem.

Well this is certainly ironic. I bought an old flail mower yesterday and guess what, it's a Mott 72 just like yours I think. Upon taking the bearings off the (drum, shaft, cutter bar) whatever you call it I noticed the bearings extended side faced toward the drum and the bearings extended side faced away from the drum on the non pulley side. The bearing on the non pulley side had grooves (3) cut crossways of the two grooves that wrap around the bearing that would allow grease from one groove a passage to the groove with the holes in it. After looking at a parts list for an Alamo 74, newer version of the Mott 72, the bearings are turned the same way the extended side faces in toward the drum on the pulley side and away from the drum on the non pulley side. This is real confusing to me but thats the way its designed. I'm like you and thought one of them was put inside out until I checked a little further. The site was Alamo's. I down loaded the PDF file but its just for a little reference and a lot of parts are different and a bit more modern looking.

You may or maynot notice I'm not a photographer

the picture of the bearings and the housings below them were the way they were oriented when removed. The one on the right was on the pulley side as looking at the mower from the tractor. You have to look closely at the bearing on the left (non pulley side) and you can see the groove cut in between the two grooves that encircle the bearing.

The bearings are the same size and will install either way however they have different part numbers so I guess the crosscut grooves is the difference. The housings on mine are indentical and have the stop for the bearings as shown where I'm pointing with the pen.

Note: The part numbers I mentioned above were from the Alamo site and may not be the parts that fit your mower. I was just noting they have different numbers for each side and the PDF makes a point to address which way the bearings should be installed. I usually buy my bearings locally rather than through the manufacturer and if the width is sometimes different I use spacers or bushings for shimming. Washers don't make good spacers for bearings and you can buy the right size spacers from places like Mcmaster Carr. 99% of the time I can get the exact size bearing but some old junk I work on might need proping up a little.

Steave · Jun 23, 2016

From your picture above it appears the two pulley's are a different type. It's kind of hard to tell but the spokes of the drive gear pulley are rounded and the spokes of the drum pulley are more squared off. Of course this wouldn"t matter but you might want to check the distance through the hole in the pulley. My two pulleys are identical with the same numbers stamped on them and it measures 1 5/8" through give or take a few thousandth's.

You may already have yours up and running just thought I'd share this info with you.

jonsstihl · Jun 24, 2016

sure looks the same from what I can see. Take a look at flail masters catalog you have the newer style self aligning bearings I bet your cutter shaft diameter is larger than mine. mine is two inches without measuring the lugs. I am waiting to order the one bearing and a few clips rings and blades. I should have it up and running by the end of july. my bearings don't have set screws at all. My mower must be an older version of yours.

jonsstihl · Jun 24, 2016

Don't use a standard bearing. those are self aligning bearings. Do a search for seal master sk-945 on the forums, someone else has tried a standard bearing and they lasted about 45 minutes. The seal master sk-945 is supposed to be the bearing you have at least it looks very similar from google images.

Steave · Jun 24, 2016

I might have known it, those seal master bearings are expensive. McMaster Carr has one I was looking at it's $48. My Mott is pretty old it would be a guessing game which one is older. I'll check later tonight about the one you mentioned. Seems like I run across those in my searches. Talked to someone at Flail Masters today I'll have to check on their prices. Page 3 shows the bearings in their catalog. Thanks a lot for the help. I'll let you know if I come accross some useful info. I'm itching to try this thing.