If it is anything like a 252[wich also uses a jackshaft],depends on wich belt you are talking about.
If it is from the motor to the JS you have to first loosen and slide the belt that powers the hyd. pump,then loosen the 4 bolts that attach the motor to the machine[should be slotted] ,then slide the motor towards the JS,install belt then slide motor back ,and go thru everything in reverse.
If it is the JS to cutter wheel belt, you use the slots in the JS bearing to get slack for R and R.
I have found ,that to properly align everything you must adjust all pullies in the following order.
1. JS bearing on the cutter wheel side [adjust for proper tension
2.JS bearing on the opposite [align the JS shaft straight]
3.Adjust the tension on the motor to JS belt via the slotted engine bolt holes in frame.
4. Adjust belt on hyd pump.
Hope this helps.