Here is a video of what the noise sounds like. Sorry it took so long. Between 12hr work days, the gym and 40mph winds it was kind of hard to get a video. The winds kept me from opening up my garage to let enough light in so we can see the vid. Also, when I watch the vid it makes the chain seem like it is way out of specs but I assure you it is not this way in real life. However, I did tighten it just a quarter turn after and the noise is still there. Let me know what you think.
YouTube - ‪Noise from front sprocket: Honda 919‬‏
It may be the angle, but you chain looks way way tight to me.
The spec is 30 - 40 mm of free play at mid point along the run.
I never run less than 35.
Yours appears to be around 25.
I hear the knocking, a very distinct knocking at that.
With the chain not being slack, it is impossible for chain rub being the source.
The chain appears to track nicely and make the tight radius turn at the front sprocket without any difficulty.
What is the condition of the front sprocket teeth ? What little I see suggests decent to OK, but the question needs to be asked.
Also, if you grab you chain half way around your rear sprocket horizontal to the axle centreline, and pull it away horizontally, how much does it lift off ? Just a bit ?
If you give your rear wheel a good shot with your foot so it spins quickly for a few revs, does the chain appear to track without kinks and tight spots ?
Now for a wild "maybe guess" IF you find all is good, in other words chain and sprockets are OK.
We can be pretty sure that the chain is not contacting at any point.
The knocking sound does not sound like the snapping sound of a duff chain with busted or tight rollers on the ping.
So, what can make a knocking sound like that ?
MAYBE a toasted countershaft bearing as sits in the engine case right behind the front sprocket.
MAYBE from excessive chain tension.
Remove the front sprocket, and hold the chain away from the countershaft (wire it to some handy place or bolt) and try to do a countershaft bearing check.
Rock the countershaft.
Turn it over by hand in neutral.
See what you can feel.
Pre 1973 CB750 Hondas were known for knocking out countershaft bearings, and drag starts were the primary cause, but too tight a chain was also known to be a cause.
I doubt very much that a duff wheel bearing is signalling that strongly up to the front, but that's another thing to check as well.