Have you changed to a different oil recently? Funny thing is my truck does the same damn thing. When cold sounds fine. After it is warmed up I get a loud valve tap.

 

Got the front rocker cover off today, and found what looks like highly airated oil goop stuck all over the inside of the top cover. Rest of the rocker box was clean. Im guessing the breather gaskets or the O ring under the rocker support plate are failing at operating temp. Replaced all. I'll go for ride shortly and see if that's sorted things out.

 

Update, nope, didn't fix it.....

The search continues tomorrow.....

 

First steps should have been compression and leak down test; cold and at operating temps to verify the condition of the top end. IT would also help if you can confirm if the noise is from one cylinder or both. While running, pull a plug wire and note if there is any change in the noise.

The noise sound like piston slap but piston slap would present just the opposite; noisy when cold but quieting down at operating temps. Drain the oil to see what it looks like; it should look like the goop in the rocker box. If that goop is what is lubricating the pistons/rings, bad juju can/will follow. Is there anyway you could have gotten water in the oil?

 

Changed oil out 3 times in the last 6 weeks (3 times I've been into the Camchest), on each occasion oil dumped out was normal looking, (no milky discolouration typical of water mixed in). The goop seems to be in rocker box only, and what is odd is that it is only on the underside of the rocker cover. Rest of the rocker box was clean, so something is spraying the oil (possibly at too high pressure, seems like the oil has been atomised?) up onto the bottom of the cover.

Im also not losing any compression, there is no power loss between quiet and noisy, and bike pulls like a Cam'ed 103 should.

99% certain its not piston slap, jugs are barely a year on (and less than 3k miles) from rebore, and new pistons. And tolerances at time of build where spot on. No way it could have worn that much by now.

Will try the plug pulling test and see if that turns up something, and pull the rear rocker cover tomorrow as well to see if there's goop inside there.

 

I don't believe the noise is piston slap either but you don't know if you are losing compression if you don't check. Additionally, just because the build tolerances were spot on doesn't mean the cylinders stayed true and the build tolerance remain intact. Poor tune, poor break in, sometimes just bad luck; I have seen cylinder bores go south in less than 500 miles. They do get noisy though and pretty quick but seems we have ruled piston slap out. Report results from checking the other rocker box and also checking the one you recently cleaned to see if what ever you did corrected the problem but I think probably not. Puzzling issue, has me scratching my head and I know you must be ready to bang yours against the wall.

 

yeah, kinda driving me nuts. unfortunately compression test requires tools or cash that I don't have. I have no external oil leaks on any gaskets that might hint at compression loss either.
Pretty certain the noise is the Rockers smashing about from being under lubricated, question is why is the oil turning to goop in the rocker box????

I hope I don't have a situation that requires pulling the motor apart, just got the dang thing back together only a year ago!

 

this is what it sounds like from a cold start, compared to the clatter that developed when warmed up in first post video.

 

Try cleaning that dirty hog.....might sound better.

 

Fix it before the dyno appointment! Only have it tuned AFTER everything is operating properly!