how often should you change the hyd.oil in the surge chamber on the hbv160..???

not sure, but on the olins,its every 2 weeks i believe, figuring it goes out evey day

The HBV surge chamber is mechanical, so it does not require frequent maintenance, other than checking the oil level. That should be 1/2 way up with hyd oil. 2 qts.

Pay attention to the build up at the bottom of the chamber. The piston bolt should be touching the cross support. DO NOT stick you hand in to feel. You can see this with the exhaust cone opened. If the build up is too great and the head of the bolt is not resting on the stop, then the chamber should be taken apart and cleaned.