Topic: Broken camshaft on 1980 CB650C 18k miles

[UNSC-ONI]

So i rode the bike all last year with no issues or noises of any kind. i parked it over winter and when i came back in the spring to get her going again i tried to start it and it couldn't get it to turn over so i went to turn it over by hand and discovered it bound up at certain points so i started to tear down the engine and found that the "ear" for the cam sprocket broke and that caused it to bind up. i'm still confused by how this happened just sitting there considering it had no issues last fall. any insight would be invaluable. Thanks

[kerryb]

Makes me think of the number of kid's stories that include:  "It just fell off, I didn't do anything!"

Actually I think it was broken when you put it away in the fall, but no one could tell because the parts fit together so well they held themselves together until...  the weather got cold enough.  Something shrank enough to let the other piece move, just a little, then when you tried it again in the spring there was enough room between the parts for something to fall off.

Lucky it didn't fail while the engine was running, there might have been a lot more damage.

[Scott S]

 Those cam lobes look to have a little unusual wear, too.

[Jerry Rxman Griffin aka MuthaF'er]

Fate or luck. That's it.

[Flyin900]

Those cam lobes look to have a little unusual wear, too.

+1 there as I think you have a top end oiling issue and you would be best to check the journals closer too when you pull it apart.

[seanbarney41]

Uhh yeah...how about a picture showing the outermost cam bearing journals...that is where the most severe damage occurs in the event of oil starvation...then when you shut it off the bearings sieze...next time the engine attempts to turn it snaps the cam chain sprocket ear off the cam or breaks the cam in two.

[ekpent]

  I broke one randomly on a 750 once,no other issues caused it. The good news was I went to a swap meet (pre-internet days) and bought a donor engine for 100 bucks and when I retrieved the cam and pulled the head there was a Russ Collins 836 kit in it. Put that in also    Could still get rings back then though I put the scrapers in upside down the first time

[Tim2005]

Were the missing part and bolt still in situ, or are they down in the sump or wherever?