I have a 16,5HP Briggs & Stratton Engine model 28W707 Type 0121E1. Had it for 16 years and did some minor repairs including valve adjustements. Shortly after the last valve adjustement, I had a major failure that initially I thought was incorrectly adjusted valves. When opening the cover I found that the inlet valve push rod was broken, basically after 2 cuts after the adjustement and inspection (it wore out where it goes through the (seal?) plate. I bought a new inlet valve ord, but then when installed and rotating the engine the rod does not move at all. The exhaust valve does move normally. Could a broken tappet be the problem???? I could not figure aout any other explanation, but if so this could be a major repair.... any suggestion?