raise or lower the left bearing support 50 with respect to the engine frame the stainless steel front roller 14 extends transversely between two front roller end bearings a quick dismounting of the stainless steel front roller is possible since the arm 50 is held removably against the channel only by the illustrated cap nut and a plate a similar front roller adjustment knob 24 is provided on the right frame side fig1 fig2 also illustrates how another cap nut 56 and a left conditioning roller adjustment knob 27 on a threaded rod are employed to fix a left conditioning roller vertical support arm 52 this is shown in an explosion view to illustrate a normal disassembly with respect to the frame and the conditioning roller 16 an equivalent conditioning roller vertical support arm adjustment structure is provided on the right side of the engine bed support frame with a right conditioning roller adjustment knob and associated rod identified at 26 fig2 also shows a guide support member 64 upon the engine bed and an inner view of the right sliding bolt and nut assembly 55 which is a mirror image to the sliding bolt 54 which provided for the left side also shown in fig2 is a pinion 58 which is outboard of the right vertical bearing support arm 53 and is keyed upon the lawn conditioning roller shaft the pinion 58 is driven through a novel pivotable gear housing as described hereinafter and illustrated in fig4 having described.