So over the past few weeks, my bike developed a strange, intermittent symptom. When stopped at a light, I could feel a "knocking" in my handlebars. This did not happen every time I stopped, and seemed random. I have a Leo Vince Corsa exhaust, which is quite loud, making it difficult to listen for any engine noises specific to the motor. It also didn't help that whenever I reached my destination and stopped to put my ear to the motor, the noise was gone. The bike had approximately 28,300 miles on the odo (~48,000km).
It's hard to describe the noise; but the feeling was almost like bearing knock, or when you lug the engine, just more subdued. Of course, I tried simple things first: make sure it wasn't noise from the brakes floating (no brakes applied), or clutch noise (same in neutral). Nothing alleviated the random noise. Being as paranoid as I am, I changed the oil and noticed nothing out of the ordinary (metal shavings, etc), but the noise did not improve. Next on the list was the dreaded cam chain tensioner. It seemed my symptoms were identical to someone else's on here that described it as a "ticking felt in the handlebars". So I decided to check the action of the tensioner to make sure it operated properly.
After removing the tensioner from the bike (had to get the clutch cable out of the way to have room), everything checked out. The spring extended the plunger when released, and the worm gear retracted the plunger when turned. All of the strength in my hands could not push the plunger back in when extended, meaning it was still supposedly locking itself in position and not backing off through engine vibrations and such.
As such, I cleaned the tensioner, fully retracted and released the plunger a few times to make sure the action wasn't binding, locked it in place, and re-installed on the bike. I then released the plunger and heard/felt it extend inside the crankcase. Much to my dismay, the noise is still present and has not improved, so I have ordered a new tensioner which should be here Saturday.
I will post results of the new tensioner, which is an OEM Honda automatic tensioner (horror stories about the manual ones; too paranoid). I do hope this fixes the problem, as most videos/descriptions you hear about these failed CCT's sound absolutely horrible, like metal slapping metal continuously. This was never that pronounced, but you could definitely tell something was off and it was doing something it had never done in 5+ years.
If the new tensioner does fix the problem, hopefully this will help others with the same symptoms catch theirs early, well before it gets to this point: https://youtu.be/KJVqwzrsJfg?t=1m15s
P.S. This guy has another video about how the tensioner works, and how to retract and lock the plunger without Honda's special tool.
Seems this is VERY prevalent on CRF250L's.
Seems those that simply have worn/broken springs, as long as the retraction mechanism is working properly and keeping the plunger from backing out, you could simply turn the mechanism counter clockwise in small increments to take up the slack. But I'd rather just replace it.