G'Day Pengs5 I'd go with the channels helical and look at one of the latter concave if you need to replace that! were coming to the conclusion that we need to have the rotor rasp bars as close as we can to the the cage (just missing the helical!!!!) and so were look at shimming out the full length of our rotor! In small grains is a good idea to close up the front of the concave to at lest 3 mm when top back check bar is touching highest rasp bar, the add filler bars to get the thrash you need! (if you can get it threshed right sorting and cleaning come much easier!!!) Im not familiar with a N5 but I would think the principles would be the sameIJ!IJ!IJ!IJ Hharvesting lentils at the moment that were frosted and then heat treated in late October (37C). 1.5 tonne _Hectare up to 8 km_hr still have a 3 ton_Ha MOG but not many lentils, oh and this is with 240 rotor revs too, and concave closed down to 4 to 5 mm and four filler bars installed. Have stop for the moment as our AC died again and driving around in 35+ degree heat is not comfortable!!!!! send me an e-mail and I let you know my number. Rolf