Rod bearing inserts, interesting

I have pulled the spare engine for my 70 750 apart and noticed marks on the timing side of the crank. Looking closer I noted that the drive side which was the side that had the stuck piston had no marks on the crank. Then I looked at the rods and the inserts and noticed that there were 2 different style inserts. The one on the drive side was solid except for the hole for the oil. On the timing side the insert has a groove going all the way around and corresponds with the marks on the crank. The crank has been taken apart and the sludge trap cleaned with very little sludge inside. I would have expected more wear on the drive side and not on the timing side. This will be an interesting rebuild and will take longer than I thought but better to take my time and do it right the first time.
I will post pictures of what I am talking about.

Interesting. I've replaced a lot of Commando rod bearings, from several different manufacturers, and have never seen any style except the plain bearing, with no groove. I've seen car main bearing shells with a groove all the way around, but not rod bearings. Maybe someone else can shed some light on them.

Ken

lcrken said:

Interesting. I've replaced a lot of Commando rod bearings, from several different manufacturers, and have never seen any style except the plain bearing, with no groove. I've seen car main bearing shells with a groove all the way around, but not rod bearings. Maybe someone else can shed some light on them.

Ken

Click to expand...

Yes, His rod bearing groove was custom machined -by a piece of metal hanging out of the oil delivery hole. [he sent me a pic.] Jim

Had mine redone this last winter. Both plain bearings. One was standard size and the other was 0.10 OS. Builder said it would still work and it does.
This was from a previous repair. Bike runs great.

The grooves on car main bearing shells are because of the oil routing, the oil comes into the main bearings from the block not the end of the crank and the oil not exiting through the sides of the bearings travel through the groove and enters the crank before ending up at the big ends which are normally plain.

A mystery indeed.

There is no mystery. It was in-inadvertently machined by debris stuck in the oil hole.