Thanks Folks.
The pin moves TOO freely in that it readily falls out on dismantling. In other machines I have worked on there has been a bit of friction in the mounting post holes.
I was lucky that I put the seat in in the correct orientation - though did this on gut feel rather than having been able to find info.
In the end, and in desperation, I wondered whether the needles were the same - they sure looked it. When I took the new one out (again) and compared it with the original (which was apparently in perfect condition) I found that the new one was about a millimeter shorter than the original one! Hoping against hope that this was the issue, I put it back together using the old needle. I reasoned that a longer needle might cause sufficiently more pressure at the seat to make the seal.
It worked!
Beats me why a genuine part would differ from the part in the mower to start with. The local mower shop and I independently identified the B&S part number.
Folks, Thanks again for your help here. I sure will keep perusing the board.
vwq47
downunder
