I put Bitubo shocks on my 2005 PX150 a few months ago. The front is the YAV with spring preload and compression adjustment. The scooter only has 1400 miles, and about 400 are with this new shock. It was a perfect fit bolting in, and the only issue is that the spring is a little too stiff to meet the minimum sag reccomendation. In other words, I have the preload adjuster all the way down. I have been riding with the compression damping at minimum as that is most comfortable.

When I drive over sharp edged bumps I hear a knocking from the front, and it is more noticeable if it is many in a row or a long stretch of bad road. I usually don't hear anything on isolated bumps. I have tried adjusting damping to both extremes and several points between, and it doesn't seem to change much. I really can't tell if the noise happens on the compression or rebound because it only does it on short/sharp cracks and edges.

I thought it might be chassis jacking and hitting the upper internal shock stop on rebound, as I am tall and ride pretty far back on the seat. That might be the reason i can't set the minimum sag. Anyway, riding much further ahead on the seat, which compresses the front shock more, didn't change the knock.

I finally put the stock shock back on to verify, and sure enough, it is now quiet. Do I have a defective shock or what?