550F vs 550K tanks

[Grewth]

Could some kind person,  with a CB550F, please manage to run a tape measure along the tank, and post up the overall length please  ?
No rush, my 550 is a "back burner " project.
I'm asking because I've got what I thought was a half decent 550F tank, but I've read here and there,  that the K model tank looks very similar,  but is actually longer.
I guess that this refers to the later K model tank with the flush filler flap.
I've tried looking at various photos of the F and the late K models,  and TBH, I can't seem to see anything in it.
Obviously,  if I've got the wrong tank (there's no paint on it to give any clues), I'd really like to find out before I put any work into it

[mickwinf]

pretty sure all the flush cap type ie F1 F2 and k3 are same just paint difference. earlier 500/550 are a different length but all will fit any 500 or 550 frame as long as you use the matcing seat.

[Grewth]

Thanks for that.
After looking at loads of photos,  comparing the orientation of the rear of the tank to the vertical frame tubes, I've concluded they're the same length.
However,  the K3 side panels wrap around the air cleaner plenum chamber,  while the F panels don't.
This makes it look like the K3 tank is actually longer.

[3scs]

K3 and f2 tanks

[Oddjob]

Mick is correct. The F and K3 tanks are the same, the 550K1/2 however are the same as the 500K, shorter. Match with the correct seat and like Mick says, they will fit the frame.

[Grewth]

Many thanks all !
BTW, I had a nice 500 tank with the bike that Bryan donated to me.
Only slight attention required........ [ Guests cannot view attachments ]

[Bryanj]

Wont petseal cure that?

[neat street]

maybe a little to far gone for lead filling, but you could try :-)

[florence]

if not concerned about originality, the 750 tank fits as well.  I've got one on mine.

[Laverda Dave]

Wont petseal cure that?

🤣🤣🤣

[Bryanj]

You remember petseal then Dave

[florence]

the paint looks pretty good.

[Grewth]

if not concerned about originality, the 750 tank fits as well.  I've got one on mine.

I've already got a 550  tank, but after reading stuff about the K model having a longer tank, I was expecting Sod's Law to apply as usual.
My tank has a fair amount of surface rust inside and out,  but it ain't rotten or significantly damaged.
But still nice to know that the 750 tank fits, 'cos there's plenty of them around.

[Oddjob]

I seem to recall the F tank being longer than the K. Fitted one on my 500 and the seat wouldn’t shut so had to fit the 550 seat as well before it would close ok. If you fit a K tank with the 550 seat you’ll end up with a gap between the two.

No news on that seat yet, he’s ringing me at the weekend though.

[Grewth]

I seem to recall the F tank being longer than the K.

See reply #3
Actually CB550 folklore seems to suggest that the K tank is the longest, you're the first person I've heard from who thinks it's the  F tank which is longest