Topic: First CB750

[70CB750]

I put motobatt batteries in all my bikes no chance of them leaking.The one in my Trophy 1200 is even mounted on its side
Why risk broken chains or acid stains.

+1 on motobatt, safe and 4 posts too.

[calj737]

So do you think I'll need to strip the engine back down to search for broken pieces in the crank case? Also it seems like aluminum and jb weld work as a quick fix for this. It's this something you guys would do or should I just start searching for a new case?

This is a customary approach to fixing it while in the frame. I would encourage you to drop the oil pan and confirm no contamination of shredded or chipped aluminum is running around in the engine.

[SOHC4 Cafe Racer Fan]

I think Kev's concern is that the chunk of crankcase had to go somewhere.  And one possible trajectory for at least a bit of it was inside the crankcase. 

[Rangle]

Thanks guys. So I guess I'll do an oil change and pull the oil pan to check for metal shards. If I find any I'm guessing the next recommended step is ripping that engine back out. At least I'm getting some hands on experience haha.

[SOHC4 Cafe Racer Fan]

Count yourself lucky.  Throwing a chain is no joke.  The chain can whip and rip parts of your leg off and/or bind on the wheel hub, seize and down you go. 

I had one go while canyon riding on my sportbike -- thankfully with no crash.

[Rangle]

Count yourself lucky.  Throwing a chain is no joke.  The chain can whip and rip parts of your leg off and/or bind on the wheel hub, seize and down you go. 

I had one go while canyon riding on my sportbike -- thankfully with no crash.

You know I was thinking I got pretty lucky after I saw what it did to the crank case. I had never heard of that happening before though so I wasn't too sure how common or how dangerous it was.

[calj737]

After you resolve the case damage, replace both front and rear sprocket and chain. Then adjust the tension properly. Make certain the adjuster is restricted also. Could easily have been a case where the axle adjuster let loose, over stretched the chain, then SNAP!

Driveline components on bikes need regular looking after. Especially "new to you" bikes.

[SOHC4 Cafe Racer Fan]

Count yourself lucky.  Throwing a chain is no joke.  The chain can whip and rip parts of your leg off and/or bind on the wheel hub, seize and down you go. 

I had one go while canyon riding on my sportbike -- thankfully with no crash.

You know I was thinking I got pretty lucky after I saw what it did to the crank case. I had never heard of that happening before though so I wasn't too sure how common or how dangerous it was.

Sometimes it's not taking up excess slack in the chain; sometimes it's a worn, damaged or compromised chain; sometimes it's a worn out sprocket or one that breaks.  On mine, the teeth of my rear sprocket broke under load (throttling out of a turn) and the chain was thrown off. 

Cal's advice is good about replacing both sprockets and the chain once you sort out the case damage.  You can run a search on the upper left as to case damage or repair.  A good welder should be able to repair the damage.  Unfortunately, you will be splitting the case to get there, so you will have an opportunity to inspect the lower end.