Lower engine knock

[airenping_imp]

Okay, got three videos for you.

Sorry they are youtube links.

1. Cold start, sounds normal.
https://youtu.be/ZVpvDTU_4-Q

2. After a couple minuets, noise starts to come on. https://youtu.be/tF2HIEWho5Q

3. About five minuets after cold start and getting louder.
https://youtu.be/0Q1aHhBEwgI

Something I noticed today was after about 10 minuets of running it stopped making the noise at idle. But if you took it just off idle it would make the noise and as you increase the throttle its still there but gets drowned out by exhaust etc.

Thank you, ping

[pekingduck]

Be sure to send the dealer those clips or the link. It may be hard for them to notice something when the engine's warmed up.

[PowerDubs_imp]

Sounds horrible.

Has anything on the engine ever been apart before?

Doesn't sound like a rod knock to me.

[jtopiso_imp]

I once let an old Lancia with too low oil level, so the oilpump "starved" for a fraction of a second during cornering (I saw the red light, but that's already too late).

After that, it made the same awful noise as your videos. After some heart surgery, tt was cured with new conrod bearings (big end) and some grinding on the cranckshaft. Only the bearing surface of two of the four conrods were affected. It lived a long life after that.

But that was an old Lancia which drunk almost as much oil as fuel. I've never seen any oil consumption on my CB.

[NovaCB1100_imp]

Thanks for sharing. I don't think its a rod knock either. Perhaps maybe it's a collapsed lifter or a valve(s) out of adjustment. Definitely share those videos with the dealer. I hope it is nothing too serious. Good luck.

[Stichill_imp]

Might use a piece of rubber hose as a "stethoscope" to pinpoint exactly where it's coming from.

[Houtman_imp]

Even a long blade screw driver will help you to pin point where the noise is coming from.

[pekingduck]

He's way ahead of us with the stethoscope - see post #9

[zirconxi_imp]

My CB1100 also making such knocking noise after warm up, albeit not as loud. I had to get my ear near to the crankcase to hear it, risking a toast ear. But at idling, definitely can hear a faint knock once warm up. And it change when I engage gear and put on some load. Is there other symptom if the bearings are toasted?

[Cormanus]

A big-end bearing died in my Honda CB175 many, many years ago. I remember only that (a) it wasn’t cheap to fix; and (b) it made a very solid and regular knocking noise (not at all faint) which is what told me something was wrong.