What part fails in a hydraulic lifter/tappet to make the clatter/noise?

 

either loose push rods if there adjustible or the roller bearings in the lifter have fallen out or the lifters have some junk in them and there not pumping up

 

Cheers blackbear.
Still using the standard push rods,and the the roller bearings are good,we've washed them out,and now putting it back together so it remains to be seen if it'll cure the racket.

 

If you have a screen in your oil pump......clean it. About 30,000 miles ago my lifters started to make a racket. Cleaned the screen ,new oil and filter and it never happened again, just say'n

 

for me tappets are noisey when the oil has air mixed in, foam, bubbles on dipstick or when oil gets hot & thin. changed oil, installed Baisley spring and it sounds good overall, no more metal tapping sound

 

What bike do you have, Year, Model?
I have checked with a decibel meter and I am getting 77 decibels at the engine near the cams on a 2012 103"
The 103" is a loud clattering motor! Drives me crazy but I got use to it.

 

One more thing to check. A minor exhaust leak at the cylinder head can make a noise much like a noisy lifter. I know this from experience. Check your exhaust flange nuts for correct torque, especially if you've changed your pipes. The gaskets tend to settle over time and small leaks can develop.

 

Cheers people, I'll check out some of the suggestions, it's a mates bike and had the SE cam plate upgrade done 1200 miles ago,then recently a tappet noise started ones more prominent than the others.

 

Update.
new lifters fitted and things are all quiet again,but would sure like to know what was wrong with the old set.