Wookie
CB750 Member
New to forum and 1st post. Bought a project bike and got burned. Found the #3 piston not moving while turning it over by hand, so I began to tear down the motor. Found what was left of the rod and the piston skirt in the oil pan. After spitting the cases I found gouging from the rod on the inside of the lower case. The #3 rod journal is marked up (you can physically feel it) and you can see the heat discoloration in the crank around the #3 rod journal from what would appear to be it getting very hot. I found the rod cap with the bolts and nuts intact, so not sure if the rod broke apart somewhere else or if it spun a bearing, got hot, then came apart. You can see the damage in the photos. Rest of the crankshaft looks good, although I still need to make sure it is in spec. I have since bought two 82 750's supersports as parts bikes, but they are all apart. One of the bikes was involved in a collision and had bent forks and looks like some case damage on the clutch housing and alternator area. I was told that one of the motors was running. Not sure of the condition of the other donor motor. Will be checking on those two motors shortly. Just trying to wrap my head around salvaging a running motor out of everything I have.
Question:
#1 Are these cases destined for the trash pile? I am pretty sure the cases are toast for obvious reasons. Although there was no physical hole in the case, there are what appear to be stress cracks on the exterior of the case right were the gouging is on the opposite side. My gut is telling me finished
#2 Is the crank destroyed?
I was trying to get two running motors, but I think I'll be lucky to get one out of this mess. My goal is a cafe racer style bike. I wanted to hopefully go with a 836 kit, for a fun street machine not a racer. Just was looking for some direction as I begin to peace things together. Thanks in advance for your help.
Question:
#1 Are these cases destined for the trash pile? I am pretty sure the cases are toast for obvious reasons. Although there was no physical hole in the case, there are what appear to be stress cracks on the exterior of the case right were the gouging is on the opposite side. My gut is telling me finished
#2 Is the crank destroyed?
I was trying to get two running motors, but I think I'll be lucky to get one out of this mess. My goal is a cafe racer style bike. I wanted to hopefully go with a 836 kit, for a fun street machine not a racer. Just was looking for some direction as I begin to peace things together. Thanks in advance for your help.