Topic: 1972 CB 500 won't turn over

[sparkadv]

New to the Forums. Read a lot, but haven't really started talking yet. A buddy and I share a 1972 CB 500 and a 1974 CB 500, and we just love these old Hondas.

Anyway, I've got a problem I was hoping you guys could help with. I was riding with a buddy yesterday afternoon and everything seemed fine. We pull up to a stoplight and he notices a bit of smoke coming from above the trans. We pull over to check it out and it looks pretty dry under there. I go to start it again and the engine barely turns over and then stops. Repeat, same thing.

I try to kick start the engine and I can't turn it over! I get off to check the oil and the fluid level looks okay. I did notice that there seemed to be a light little bit of smoke or something that came out of the crankcase when i removed the dipstick.

A little more data. The engine won't crank from the starter. I can't seem to kick it over without using a tremendous amount of force. I can kick the kick start freely with the clutch in. With the kick start 3/4 of the way down, the rear wheel becomes harder to turn, but not impossible by any means (on the center stand). I can roll the bike freely in neutral. It all leads me to believe it's engine and I've got a seized bearing or something, but I'm honestly not sure and don't know the bikes well enough.

Anyway, I had to call a buddy to put the bike in his truck bed to get home. Not sure where to start. Anyone seen anything like it or heard similar stories? I'm going to start tearing it apart when I get home from work today. I plan on starting by removing the plugs and the crank case and then spinning the motor manually.

Anyone know anything on the transmission side I should be checking too?

Thanks!

[bryanj]

Sounds like you may have siezed the engine--usually the camshaft which means another head; cam cover(with rockers) and cam plus possibly worse in the bottom end. Usually happens if the oil pump suction filter (inside the sump) hasnt been cleaned

[chopstar500]

Sometimes when these old SOHCs get real hot (see that you're inb Cali) they can "seize" up temporarily. I've read posts here about that very thing - some have reported this condition, and stated that after cooling the engine was fine (not even any scores on the cylinder walls).

Do a quick search... I read a post just the other day about this. Keep us posted & good luck.

[Hush]

Read the same post about possibly siezed motors freeing up after being left to cool.
Not sure who wrote it but he stated that the same motor was still running fine years later with him doing no work to "fix" it.
Hope it is just a wee problem and nothing big.

[sparkadv]

I think that's probably the exact issue. I pulled it apart last night. Found a few things of consequence.

1) Oil filter had some shavings in it and was dented in
2) center cam chain cover bolts were really tight. the metal was really soft when i tried to loosen the bolts with a phillips, so i had to use a vise grip. 2 of the 6 bolts broke while coming out too. They were covered in a white powderish film. Here's a picture
3) everything was still seized even after it had cooled down.

Thanks for the help guys

[bryanj]

Sorry but description of filter suggests that it aint been loved, white on screws is probably they never been out--nothing to do with heat. Personal opinion---you are in for an expensive rebuild BUT will be happy to be wrong