Drive belt came off idler C85

[JackHorse 11]

Hi Guys, Had a random occurrence this week. Mowing along with my C85 eight speed in 1 low (grass was thick and wet), went to depress clutch and the drive belt jumped off the idler. I've had this tractor 3 years and it's been working great.  The belt itself looks good except the top of it was a bit chewed up in a short section which I believe happened after it came off.  I put the belt back on and continued to mow with no further issue.  Any ideas as to why this would happen or adjustments I might need to make to prevent another incident? Thanks 

[stevasaurus 23,808]

Check the alignment of the pulleys and also... see if the little keepers have not slipped to where they might interfere with the belt when the belt is in action.  It does not take much to start heating up a belt.  Also, those keepers may have to be adjusted.  Just went through all of that with my 876. 

Just riding the clutch can heat up the belt...like you might be doing in high, wet grass. 

[953 nut 68,699]

There should be a tab over the idler pulley that keeps the belt from coming off of it.  Also the engine should have a small clip which is about 1/4" round stock that will keep the belt in place at the engine pulley. Finally your belt guard has a track at the bottom that will stop the belt when the clutch is depressed. If there id any question about the condition of the belt I would suggest you replace it. If the belt gives out it will pick the most inopportune time and place to do so.          

[stevasaurus 23,808]

Richard is correct...I had some of those guards slip a little and become some of the problem instead of part of the solution.     check those out...both in and out of tension. 

[JackHorse 11]

Thanks for the responses guys. So the tabs and clips should be close to the belt without rubbing ? Maybe 1/2” clearance or less?