I'd like to share something with you on the subject of clapping hydrostössels.
Apart from different types of oil, the hydros clack especially when the bumps are clogged or dirty in the long run. LM back or forth.
I once had such a problem with my URI (90Q / KV engine, 260tkm). And that's how I solved it.
1- When the bumps are all outside, soak in petrol over night.
2- Clamp the ram in the vice, in such a way that a metal object (e.g. Presses a 6 nut on the small, spring-bearing pushbutton. The ram doesn't scratch, because very hard steel.
3- Tighten the vice, open it again, dip the ram into petrol and pump it manually until it is full and then manually pump the black broth out.
Repeat 4 points 2 & 3 until the petrol comes out clean. Of course, at 32 Hydros it does more work than at 10
5- After assembly, run for 5-10 minutes in idle mode, and then gradually a full hum from the clacker becomes
Greeting Guido
Andi