Pull the heads and inspect the head gasket for leaks, distortion. No leaks = no distortion. Have the head surface checked for flatness. May need to be machined. Pull the cylinders and look at the pistons and the cylinder walls. Marks = no oil = bad. Pull the rods and look at the bearings and crank journals. Everything OK? Install new rod bearings. The main bearings will probably still be fine. Big ball bearings after all. Remove and inspect the oil filter. Metal or alloy = not good but probably from the piston/ cylinder sleeve's.
If the pistons or cylinders are bad I have the set from my 91 with 40k available. Still look fine. Just needs a clean up. Bolt on and go.
Total expense for the above? Rod bearings and rod bolts. Cylinder O'rings, head gaskets, head check fee, cylinders. Not as bad as it could of been.
Also your brother must buy all of the beer necessary for the above work to be preformed and stand by, watching you work in his underware, freezing his ass off. Some people have NO clue and I guess you have one. Sorry.
Steve in SF
87 Harley FXRS-SP ~ 06 KTM 625 SMC ~ 72 Honda CB750/915cc ~ 92 XR600/654cc ~ 95 XR650l/675cc ~ 03 CRF450r ~ 05 CRF450x ~ 02 XR650l/675cc ~ 86 YZ490 ~ 93 YZ80 ~ 93 XR650l Project