Hello !! Have a question to the screwdriver professionals here….am a bit talented but not of the subject !! It is an Aprilia Leonardo 125 year 1996. And indeed, in autumn 2018 the rear caliper broke during the ride. Got a used one. Also the brake lever with brake pump was replaced. Brake pads have been changed before without any problems. Only now there are problems. And we have tried to vent the brake system several times already. However, there is no clear pressure point and the lever can also be pulled through to the handle…. When the balance tank is opened, blow air bubbles at every lever actuation…. Is the normal or do I have a mistake in thinking about it somewhere? Situation/output: 1. Balance tank open and watch out for it does not run empty 2. Lower pressure pump connected to the closed brake caliper nipple 3. Brake lever several times actuated and then pulled and brake caliper nipple opened -> a little Brem liquid flows into pump tank 4. Nipples closed again continue point 3. Have about 700ml of DOT4 brake fluid pumped through with a vacuum pump……no improvement…… I am grateful for any idea !!!