I recently bought a rather nice set of used stacks from a WSB Team.

Two long - Two short. I take it the longer two go on the 'middle' TB's?

Also, these stacks slip-in to the TB aperture and at a common point across all stacks there is a threaded section. Is this in someway used to secure the filter/airbox baseplate in situ?

As you can tell - I've never played about with TB's before!

If it helps, I would suspect these stacks have come from the YEC (Yamaha Engineering Corp).

I have Graves velocity stacks fitted to mine and yes they recommend the longer trumpets on the inner TBs.

The velocity stacks all have a groove in them which locates to the airbox.

- Jim