Crank bearings good or bad

[Acro1985]

Hi All

Just stripped my engine down, and wanted people's thoughts on the crank bearings as to whether they are good or need replacing.

[Bryanj]

Oil and filter have not been changed often enough but unless you plan on racing they should be fine looking at the pictures but enlarging goes fuzzy

[Acro1985]

Try these one Bryan

I don't plan on racing it

[Nurse Julie]

I would suggest changing the ones with the marks / nicks out of them.

[McCabe-Thiele (Ted)]

If you have gone as far as splitting the crank cases a lot depends on  the situation with the pistons.  I've always replaced crank bearings if an engine is being  rebored.

[Murf]

It’s a hard thing to determine from a couple of small photos but they are a bit grey and matt looking so would agree with the opinion about lack of oil changes, or possibly stood for a long time with old oil.  It would be helpful to have some photos of the crank journals to see what they are like. The journals should be smooth with no ridges or groves you can feel using your fingernail. Measure bearing clearance with plastigauge to see if they are within specification, if they are and crank journals are good then you have to make the call on the info you have.  I guess a full bearing change is in the region of £300-400, assuming you can get a full set of the sizes/colours you need. 
I will have exactly the same job and decision to make soon, I will be factoring the future usage that the bike will be having into my decision ie it’s going to have a pretty gentle well looked after life.

[Bryanj]

Those pics are clearer and i agree with Julie, now i can see the knicks i would change that one

[McCabe-Thiele (Ted)]

Weird optical illusion on my phone with one bearing looking like it should - the second looking convex!

I need to go to Specsavers?

[Acro1985]

I think after sleeping on it despite the cost if I can get a full set of bearing I will replace them as well as the Conrod shells, as I have no history for the bike or how long it been off the road. Plus someone has clearly had it apart before judging by the excess sealant that squeezed out everywhere.

So the next question is do I need to replace all the bearings for the gearbox shafts as they do seam to be is good condition

[McCabe-Thiele (Ted)]

If gearbox ball bearings are smooth when rotating with no visual signs of surface "pick up" only ones I would replace as matter of routine are the primary drive ones. Some of the special needle rollers are pretty much impossible to find.

[Bryanj]

In all honesty whilt i have heard of the needle rollers failing on 500 i have never actualy seen a worn out gearbox bearing

[Acro1985]

Thanks again for all help and advice.

Although I was hoping someone wasn't going to say the needle bearing are like rocking horse poop.

I am missing one the little rollers for bearing on the main shaft (NR 15 on the part diagram) it fell off as I was taking it of the case to put into bag to keep everything together for the shaft and they scattered all over the floor. I have found 15 but the 16th has vanished 😭

[Bryanj]

Try looking up a local bearing supplier and taking one needle in to compare, they frequently sell loose balls and needles

[Acro1985]

Am I right in thinking you can no longer get the yellow crank bearings?? Having done some searching on the forum, and much head scratching, from the marks I can find on the crank it's 1A or A1 on at least three of the journals. On the others I can only make out the 1. Conrods are stamped 2D for three of them and 2C for one.

Sorry for all the questions this is the first motorbike engine I have completely stripped down to rebuild

[McCabe-Thiele (Ted)]

You are unlikely to need Yellows, as a starting point for your mains look at your crankcase codes, then accurately measure your crank mains in mm. If you use the search facility here there are lots of posts on the subject.

As Bryan said earlier check your crank first for any wear ridges. Beware of confusing conrod weight codes with crank web conrod codes.

PS The crankcase mains starting point codes are easily visible as they are stamped on the back of the crankcase, five letters containing A,B or C. It's extra confusing as the tables for the mains and Conrods use different axis in the parts book.

When web  codes are illegible you need to rely on a combination of micrometer readings and Plastigauge. It's always a bonus if the edge of your old shells have colour markings that are still visible - it's just a dab on the edge - the numbers stamped on the back of the old shells are just casting batch numbers so are of no help.