Tearing down my first engine and wanted to get some seasoned eyes on my main bearings. They look good to reuse? I am Picking up some plastigage so I know that will be the determining factor but just asking if The old ones pass the eye test.
They should be replaced, I am seeing a lot of bearing material fatigue and material moving around. The last photo is showing worn through the top layer on the edge.
SenseAmidMadness
CB750 Addict
How clean are those? They look like they've got drops of something on them.
I would get them very clean and then check with the Plastigauge versus the manual's specs. I would also get us some closer and more detailed pics as it's hard to tell whether they're worn shiny in spots or if it's just oil.
I would get them very clean and then check with the Plastigauge versus the manual's specs. I would also get us some closer and more detailed pics as it's hard to tell whether they're worn shiny in spots or if it's just oil.
They are pretty clean. Wiped me down with a rag and breakcleaner before the pic. But I’ll reshoot a few more cause I agree they look a bit “pitted” or something in the pics.
Again they should be replaced. It looks like it has had some sort bearing fatigue and acid damage from old oil sitting for a long time in the bearing. One of them shows edge wear that is through the top layer which could be from a case alignment issue.
looking for my journal markings. On the upper case I am seeing the below. Everything I read and watch says these should be alpha characters. But my case only have numbers??
Currently there are all greens for the main bearings as I can see the color on the bearings.
Currently there are all greens for the main bearings as I can see the color on the bearings.
Attachments
SenseAmidMadness
CB750 Addict
Got a micrometer? You should measure and inspect the crankshaft for wear too.
What is the engine serial number? It may be a very early case.
Yea came to that conclusion as well. Plus I love tools even if I may never use again.looking around OfferUp now.
Sorry for some reason I thought it was a sohc motor. I think the dohc stamped letters for the main bearing is on the top of the upper rear motor mount
Chrisraven
CB750 Enthusiast
The case letter is located on the back top right of the upper engine case. Where the engine holding bolt goes through. With that letter and the crankshaft marking you can determine the correct replacement bearings for the engine. With that said, as others have mentioned, I would mic out the crank and check for runout on the crank. You can have some abnormal wear that would cause the crank journal to be tapered from side to side, which would require you to have the crank ground. You can determine that by torquing the main bearings (without the crank in) and then using an mic measure the gap and compare that to the main journal, this will give you a really accurate clearance gap, then you can order the bearings that will give you the desired gap. You have to measure each one (I would record all the numbers) since you can have a variation from one cylinder to the next.