pay attention to the reassembly,drop the pan when you do it and be sure this dosent happen to you!the lower end is easily miscued out of its little locating well or slot,this is very hard to spot from above.
![](http://i857.photobucket.com/albums/ab139/dave500_01/miscued.jpg)
heres a shot of an open lower case i used to show where a sloppy primary chain can rub on the case,you can see the slot or well your aiming for when dropping the barrel and tensioner down into place.
![](http://i857.photobucket.com/albums/ab139/dave500_01/chainwear002.jpg)