This is the intake cam with sever wear on the valve that dropped.

This is the rocker arm.

This is the sever wear on one of the intake lobes on the other side.

And the rocker wear

 

Another picture of the rocker wear.

Here is a good rocker right next to it for comparison.

Cam area oil feed screen was clean

 

My assumption here would be that the increased clearance caused progressively more aggressive hits on the valvetrain until the valvetrain eventually gave up. That's a massive ramp in impact when the cam comes around when the clearances are that big - like going from pressing the valve open to opening it with a hammer.

Must have gotten one of the bikes with bad cam hardening, clearances grew and grew, and eventually the retainer gave up the ghost. Was the valvetrain particularly loud? I can't believe that it didn't sound somewhat off at idle with that much clearance and that aggressive of a cam ramp.

 

My assumption here would be that the increased clearance caused progressively more aggressive hits on the valvetrain until the valvetrain eventually gave up. That's a massive ramp in impact when the cam comes around when the clearances are that big - like going from pressing the valve open to opening it with a hammer.

Must have gotten one of the bikes with bad cam hardening, clearances grew and grew, and eventually the retainer gave up the ghost. Was the valvetrain particularly loud? I can't believe that it didn't sound somewhat off at idle with that much clearance and that aggressive of a cam ramp.

Thnaks, That is my thought also that the hammering broke the valve retainer.

Treed's comment along with some Facebook comments seem to point to the origin as a bad quality cam.

I've ridden with him a number of times and did not pick up on the noise, but with his loud exhaust and my earplugs and helmet, I'm not surprised.

One last clue would have been metal in the forward screen. He says he checked that when he changed the oil soon after he got the bike at about 4k miles and it was clean but has not since. I'm going to pull that screen this morning and see what is there.

Just like my RFS motors, that bottom screen tells the future and can catch bad things before they get to this point.

I thought it would have clearly been caught at the valve clearance check but that is not suggested till 18,600 miles.

 

That engine must have sounded like a hammer drill at idle.
Bad cam hardening would be my bet.

 

On my friends bike the cam chain tensioner broke and the parts destroyed the engine.
He sold the bike as parts and bought a new one.

 

Do you happen to have the build number stamped on the engine? I want to see if we can correlate certain engine numbers to failed camshafts

 

seems to be a known issue with the 890 motor. my cam was seriously worn at 18,000 mi. had to replace the head

 

I didn't know about the cam issue till I fixed my friends bike and then about that time the Facebook KTM failed cams group opened up. Many, many pictures of failed cams and followers. A recent one on a 790 dropped a valve like my friends bike.

BTW, the bike got back together early April (getting the cylinders replated took longer than expected, plus part hunting) and has over 5k miles on it with no issues.

 

What year was it? KTM supposedly fixed that issue for the 2022's and on.

 

KTM have been compensating owners out of pocket for fixing this known manufacturing defect - I'd strongly engage KTM