Finish mower belt problem

[tanner]

I have a 48" LMC finish mower that came with my Yanmar 1500. It is about 9 months old and has worked great until about a month ago when I cut a 2 acre pasture for the first time this season. The right side belt came off while cutting, so I replaced both belts. Everything worked great for the next cut. Then yesterday, the right side belt came off again. I replaced it and it came off within 10 minutes of use. The pulleys look fine and everything seems to be in alignment. Any ideas on the cause of this problem?

 

[Mosey]

Have you checked the tension?

 

[tanner]

Danny, thanks for the reply. I thought about the tension, however, it doesn't seem to matter. When I first replaced the belt yesterday, I tightened it as tight as possible. The second time I installed the belt, I backed off the tension thinking it may be too tight. Of course, it still came off. The tension adjustment is for both belts and I'm not having any problems with the left belt. How tight should it be? Is there an accurate way to "measure" tension or is it simply a "feel' thing?

 

[Dozernut]

Check your spindle bearings. It sound like you have play in a spindle shaft. When the blade on the shaft, with the bad bearings, loads up it tilts a little, allowing the belt to slip off the pulleys. You should be able to match up the numbers on the bearings and buy locally at a good parts store.

 

[tanner]

OK, I'm going to ask a stupid question! Is the spindle shaft the shaft that the pulley is mounted to? Will I be able to feel movement in the shaft if the bearings are bad? Thanks!

 

[Bird]

I don't think Dozernut is still online, so . . ., Yes, to both questions.

 

[tanner]

thanks; I'll take a look at the shaft and bearings

 

[Dozernut]

Yes, the spindle shaft is the shaft your pulleys and mower blades are attached to. This is the same shaft that you have a grease zerk on, that you shoot grease into for the bearings. You have to take all of the belt guards off and expose the spindle housing. These will be held to the mower body by 3-4 bolts. These do not need to be removed unless the housing is cracked and will need replaced. Remove the nut, holding the pulleys on and remove the pulleys ( you might need a puller). You should have a exploded diagram showing all the bearing parts and the order they go in the housing. If you are handy with tools this is not a terribly hard job, but if you are unsure contact your dealer for help. There are no stupid questions, just the ones unasked!

 

[tanner]

I checked the spindle shaft and there does not appear to be excessive movement (in fact, there is very little movement) either up and down or side to side. Other ideas? BTW - I agree fully about unasked questions being the only stupid ones!

 

[bubenberg]

turn the blade slowly, very slowly, (by hand) and put one finger on top of the spindle, if you feel a kind of slight knock you have a spindle problem. repeat that for each spindle.