Dual Seat support - Plunger

[Craigy]

Hi guys,

Can anyone share some info on a problem I have with my dual seat. It doesn’t keep its shape when used, the rider position becomes much lower.

Should it have some sort of bracket/support under it?

I’ll share a couple of before/after pics for comparison.

If anyone has any pics or part number that would be much appreciated. It’s not the rear fixing bracket. The parts book nay lists a single seat

[Greybeard]

Have you checked that the seat pan is sound?

[Swarfcut]

 Aftermarket seats (at least when I bought one years ago) lack the substantial factory design box section stiffeners running front to back, often relying on simple stiffening pressed sections instead. So it is all down to the seat base lacking sufficient strength to support today's riders.

 Swarfy.

[Craigy]

I did think this and was considering having a strengthening plate ‘tacked’ onto the underside.
If there’s no actual fixings, I’ll just get it sorted.
Cheers

[chaterlea25]

Hi Craig,
I would make some vertical supports and fit them where the single saddle spring mounts thread into the frame

John

[Swarfcut]

 Back in the day we used small square section steel box cut and welded to mimic the original factory base strengthening ribs. Also used BL Mini exhaust rubber mounts (rubber block with bonded on plate and stud) to form isolating seat mountings at the rear, easy on a custom rear seat bracket at a time when replacement parts were scarce, 1976.

 CJ's suggestion is an easier solution for now. Frame lug is threaded BSCy/CEI for single saddle spring mountings.

 Swarfy.

[limeyrob]

The BSA seats have a couple of angles about 1/2 x 9" long to stiffen the base.
There should be supports, holding the rider weight to the frame. These come in 2 varieties.
On plunger frames studs/bolts that go onto the frame and have a round rubber bung (42-9183?) on top that hold the seat up right under the rider.  Without these the seat collapses.  If you look at the many A10s they look like this, even restorations.
Large rubber blocks (42-9057) that sit in brackets on the seat base, these are a slight wedge shape and sit on the side rail of the SA frame.  Again often missing and seats collapse.