Mowing MF 31 Sickle Mower with Smoking Gearbox. Any diagnostic tips?

[Bid]

I purchased an old Massey Ferguson 31 sickle mower. I did some cleaning, adjusting, and lubricating on it and took it out for a test run. After 2 or 3 rounds I noticed some smoke coming out of the gearbox cover. Something was hot enough to cook the grease!

Back at the shop I disconnected the connecting rods from the crankshaft and inspected the two main bearings. One was in good shape and the other one seemed to have a flat spot it it. The local MF dealer had a replacement bearing in stock, so I bought it and replaced the one with the flat spot. After reassembling the gearbox I took the mower back to the field and again after 2 or 3 rounds the gearbox grease was smoking again.

Does anyone have any tips on what to inspect next?

Thanks.

 

[Sodo]

There are 2 main bearings and 2 'rod' bearings, 4 bearings. So all 4 bearings are smooth and greased yet it still gets hot? I'd run it for a little while, then shut down keep feeling the bearings until you can tell which one is getting hot. If you had an infrared thermometer this would be a good use for one.

Or you could sell it to me, I need an MF31 wobble crank and sheave in a bad way .

 

[Bid]

Thanks for the info, Sodo. I will tie into it in a couple of weekends and check out those rod bearings. I hope they're not too hard to get too.

I don't want to sell it yet. I think the old mower has some potential. It seems pretty tight and doesn't look bent up or abused. Once I get this bearing issue resolved and replace a few sections on the sickle I believe the 31 will be a good mower.

If I find a 31 that can be bought for parts I will let you know.

 

[Sodo]

Thx that would be great. If you can conjure one up sooner than later please get out your magic wand. Also you're pretty far away…. I have to s**t or get off the pot, the grass is growing. I have a homegrown repair in mind, will have to order parts soon. Even so, it's $150 of "parts". My MF31 is in very nice condition (otherwise) and I'd prefer to restore it to normal than make it a bastard.

 

[Sodo]

I've been doing some research with regard to the MF31. The bearings are no longer available. And when they were, the smallest one was $76. My advice to you is to find the cause of the smoke and get it stopped (with grease) before you ruin your un-obtanium bearings (and then have to sell me your crank)!

I have also discovered that my "forward" bearing failed, and this caused the vibration that broke the heavy (flywheel) sheave off the rear of my crank. One guy said that people like these mowers because they are vibration free (when working right). This is one of my motivators for getting mine fixed (plus the challenge). Would you say that your "Dyna-Balance" MF31 is smooth running?

 

[Bid]

Yes, this mower runs very smoothly. In fact, that was one of the reasons I bought it. The whole drive assembly rotates easily.

Sounds like you need this mower more than I do. If your interested in buying the mower send me a PM.

 

[Coyote machine]

Maybe you could have someone walk behind the mower while it's running to pinpoint exactly when it starts to smoke, so you could then try to pinpoint where the excess heat is building. You do have fresh gear oil or whatever fluid of the correct viscosity in the gearbox?

 

[Bid]

Coyote, thanks for the tip. This particular gearbox is not filled with oil, it simply uses grease fittings at several locations. What is making the diagnostic difficult is the fact some of the bearings within the box are hard to get to while it is assembled. If the cover is removed I may be able to get a high-temp paint stick in there to touch the various bearings. If the stick melts then that should identify the bad bearing. I may also try to borrow a thermal image scanner.

 

[Sodo]

Why don't you just run it for a little whiles, and feel the bearing housings with your fingers, find out where the heat is.

I re-assembled my MF 31 wobble box today. Some of the bearings would not grease, the grease was squirting out outside the bearing, not coming out the seals. To get them to grease (and grease come out the seals) I had to actually rotate the outer bearing races, to align the greaseholes with the zerkholes.

 

[The kid]

You can go to Harbour Freight and buy a laser thermometer relatively cheap. It will measure over 500 degrees. It came in handy when I calibrated my water temp gauge on the 135. It will only measure the surface temperature. Then if you see it smoking or after running it a while you can hop off and give things a quick check with it. In bright sun you would have to get close so the sensor can see the laser dot.

Non-Contact Infrared Thermometer With Laser Targeting