Up in NH riding this past weekend. Climbing a hill, starting to notice that i’m giving much more throttle than normal, machine seems a little sluggish, slowly lose power, starts to knock and rpm drop to the point where the machine would idle fine, but would struggle to just move forward. Shut everything down, towed machine out and am now ready to start looking for causes.

Here’s what i have observed so far:

Machine will start and idle fine
No loss of coolant, no smoke from exhaust
No loss of oil
Nothing present in the oil(no gas or antifreeze)
No noise at idle, but once you rev throttle, a noticeable knock comes from the engine, heard most around the head area.
Does not appear to be a fuel issue, clutch is rotating fine, even revving throttle in neutral causes the knocking sound, so I don’t think the clutch or transmission is involved.

Has anyone taken down the head on a unit (700 twin) like this, and know of any issues i should look for?

I’m thinking it’s a valve/lifter/head issue, but the fact that i have not lost a drop of oil or coolant perplexes me.

Feel free to weigh in with thoughts on possible causes. I’m going to look to post a video with the sound it makes.