I am assuming tranny drive belt here. You just said top pulley, is that the engine pulley or the tranny pulley. Engine pulley should have no wobble. If it is the tranny pulley, there could be some wear where it connects to the input shaft of the tranny. excessive movement could be part of the problem. You didn't say which pulley the belt is coming off of. If it is getting flung off the tranny pulley, make sure that the support bracket on the front corner of the tranny hasn't come loose. if that bolt is missing, will allow tranny to tilt throwing of the belt.
Sorry, I should've made that clearer. Yes it's the tranny pulley- when she come off- it don't go! Lol. Is it the bracket where you adjust the brakes? I'll try to see if a bolt is missing.
Thanks
The problem is the idler sheave flopping around because of a worn pivot point. It's the one that tensions the belt when the clutch is engaged, if this tractor is gear drive. Being careful, set brake and chock a wheel then temporarily check it by putting the transmission in neutral, starting it, engage the clutch and increase engine speed to high idle. Get off and look under the mower to watch the belt action.
If you need more free advise don't delay. It's looking as if I may not be around much longer. 0ｰF
The bracket that I am talking about is a flat plate on the front corner side of the tranny. Some have one on each side of the tranny. 1/4 inch play is not uncommon, with wear. Could be part of the problem though. that movement can't be good on the tranny shaft, or the spines in the pulley.
So if my head is at the blades looking back at the tranny, it'll be on either corner or both?
Thanks