My 06 YZ450 has a cracked free piston (big surprise I know). So I ordered a set of aluminum pistons from Smart Performance. But I can't seem to get it to bleed out. I have followed both the Yamaha directions (which I have done before lots of times without incident) and the directions on the Smart Performance site. The results are the same. When I pump the rod up and down without the valve in place, no air. So Install the valve, push the rod in and it will extend by itself once or twice and then no more. In fact it the rod develops a negative pressure (pulling itself up a bit).
Do I have he wrong piston? The new unit only has one o-ring, while the factory piston has two.... Or am I missing something?