Tank locating method?

[SpannerBrat]

Hi all,
So my cafe build has come to the seat making stage & as I’ve never seen how the rear end of a standard 550 tank fits to the frame, I’ve no idea what I’ve got to fabricate, to work up to (the piece of perforated is just a start). Can someone describe the method of locating the tank & the ultimate arrangement (with the plates, flaps, rubber piece & holes that can be seen in the photo) or direct me to a link or images etc. that will help me understand what I’m aiming at please?
Many thanks for any help offered from your immense pool of collective knowledge.
Andy

[SteveW]

The tank just hooks in the rubber block.

I was shocked when i got my 550 just how the tank is held.
The standard seat also keeps it in place by pushing it forward against the front locating rubbers.

[Nurse Julie]

Hi. I have just made the seat for my CB550 Mongrel (see pic in gallery). I have got a CB500 tank fitted but the fittings are all the same. If no one comes up with the info you need, I can take photos of mine if it helps. Let's put it this way, there are some awkward shapes that have to be made at the underside, front of the seat pan / foam to accommodate the big rubber tank fixing etc.

[K2-K6]

You need to remove your tank to get those two tab on the frame clear,  turn the rubber round and slide it towards the back of the bike so that the frame tabs then hold the rubber block secure.

Locate the tank onto front pivot mounts (should have rubber cylindrical blocks to support tank) then the rear tank mount sits onto that rubber mount you've put on the frame.

Finally,  pull the finger tab on the rubber block backwards and the tank will drop into its final place,  captured by the rubber going over the tank tab as you release the finger hold.

[SpannerBrat]

OK, so the rubber piece is 1stly, the wrong way round (that “tab” should still be uppermost but pointing towards the back of the bike) & when installed correctly, joins the tank to the frame by sliding it 1st, over those 2 frame tabs & then lowering the tank & stretching it over that flat(ish) part of the tank. Have I got that right?
The seat then just has to meet that rubber piece & follow the profile of the rear end of the tank?
Should be doable if I’m reading things right.
Thanks for the help.

[Green1]

That's it a strangely difficult process to describe but dead simple in reality

[K2-K6]

Yes you have that right. 

It does leave quote a big gap on these bikes compared to some other manufacturers,  normally covered by the thick standard seat.

Some of the modded seats show the gap but some are really good at getting the profile right to meet the tank.

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This one looks quite good at the front,  but more brat type than café at the rear.

[K2-K6]

Or this profile that rises more toward the front and covers the gap under the back of the tank more effectively.

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[Nurse Julie]

I made my seat so the seat actually pushes under the tank and takes up the entire gap of the tank profile as I don't like the look of firstly, a gap under the tank and secondly the finish of a seat with a poor fitting profile abutting the tank.

[Trigger]

You will still have gaps at the sides on a SOHC tank. You can braze a plate to the opening arch, just leaving enough gap to put the tank rubber on 

[SpannerBrat]

So I squished, pulled & slotted it into place this morning & it all worked quite simply, as described (thanks again). Just out of interest, is the hole in the bracket (flange?) that comes off the tank used? It corresponds to a hole beneath in the frame (that's larger). That particular CMS microfiche isn't the easiest to read  & I can't see anything that corresponds.

As for closing that gap, I can see it could be a tricky one but plan to solve it somehow. As it happens - although I class it as a "cafe" build - I've more of a brat seat style in mind. I might lift the nose of the foam slightly (as shown in your "Pire" pic K2) so I can follow the rear profile of the tank (or may consider moding the tank Trigger ). Squeezing the seat under the arch sounds interesting but (as mentioned by Trigger) the tank is distinctly wider that the frame at that point so will also need a bit of head scratching (but isn't that half the fun  ).

[SpannerBrat]

Actually, looking back at the 1st image I posted, the gap doesn't look that big really. So, your suggestion NG might well be a lead runner  . Particularly as it seems foolish not to take advantage of using the already upturned, press formed spaces in the frame to locate a couple of pegs within the base which means I'll be slotting the seat down & forward before dropping pegs in the rear into a bar I've attached across the back end of the frame just in front of the seat hoop.

I can feel it coming together already 

[SpannerBrat]

Anyone any ideas on what these holes above one another in the tank & frame are about / for?

[Bryanj]

Ventilation

[Seabeowner]

OK, so the rubber piece is 1stly, the wrong way round (that “tab” should still be uppermost but pointing towards the back of the bike)

The tab faces forward, but it matters not a lot as far as location is concerned and makes installation a little more awkward.