Now here's a thing...!
I was also posting about this on a worldwide FZ6 Forum on Facebook and it turns out there was a biker who literally lives just a few miles away and who'd been taking apart bikes and putting them back together for about 30 years (he'd just rebuilt an FZ6 he'd bought with a broken frame), so he offered to come and have a look at it.
Within very short order he'd got the rear end apart (which would probably have taken me several hours) giving a lot more leeway to manoeuvre and then we had fun trying to sort the bloody gasket out again.
Finally, after looking at it and checking measurements etc, he found the problem: The one I was getting was the wrong size!!
The difference is literally a matter of millimetres, but the one which I supposedly needed, according to all the searches I'd done and Fazer parts catalogues etc, that had the code 3XW-14714-00 is just a millimetre too thick at 45 x 50 x 35 (internal diameter, external diameter and height)
This meant that, although it would it either into the cat pipe or into the one from the headers, there wasn't enough space for all three bits to fit together because the pipe from the headers would make it bulge out just a little bit too much to fit into the cat pipe.
We've found another one on eBay from M&P which is 46 x 50 x 34.5 and (fingers crossed) when it arrives, everything will fit together properly.
I was also posting about this on a worldwide FZ6 Forum on Facebook and it turns out there was a biker who literally lives just a few miles away and who'd been taking apart bikes and putting them back together for about 30 years (he'd just rebuilt an FZ6 he'd bought with a broken frame), so he offered to come and have a look at it.
Within very short order he'd got the rear end apart (which would probably have taken me several hours) giving a lot more leeway to manoeuvre and then we had fun trying to sort the bloody gasket out again.
Finally, after looking at it and checking measurements etc, he found the problem: The one I was getting was the wrong size!!
The difference is literally a matter of millimetres, but the one which I supposedly needed, according to all the searches I'd done and Fazer parts catalogues etc, that had the code 3XW-14714-00 is just a millimetre too thick at 45 x 50 x 35 (internal diameter, external diameter and height)
This meant that, although it would it either into the cat pipe or into the one from the headers, there wasn't enough space for all three bits to fit together because the pipe from the headers would make it bulge out just a little bit too much to fit into the cat pipe.
We've found another one on eBay from M&P which is 46 x 50 x 34.5 and (fingers crossed) when it arrives, everything will fit together properly.