Will early model 550 tanks fit a 78' K3?

[Hudson.]

Hi all,

As title, do earlier model tanks (ones without flush fuel caps) fit late model 550's? Im after a replacement tank as is stripped mine down to find a patch of filler hiding a big dent, its also rusted through and leaking.






 

[Trigger]

Not sure what you mean by a early tank. All UK 550 tanks are the same, or are you talking about a USA early tank which is the same as a CB500 four tank.

[Hudson.]

Ah right perhaps im confused then, was this style tank not on any of the UK models?

[matthewmosse]

As far as I recall, yes they will fit, but fuel taps on earlier bikes may be 2 outlet ones so you may need to fit a blanking short bit of hose with a bung in it. The other issue you may come accross is that the seat may be either too close to the different tank or too far away ( cannot remember which ) the solution on my bike wss the seat was mounted using longer bolts and a shed load of washers were used to pack it out to sit right, I don't recall what was done with the peg to locate to the seat lock, I suspect it was just mounted on 1 bolt and a self tapper or rivett. I have a spare 550k3 tank with just a small dent - horrid paint - really horrid and it leaked and was treated with petseal many years ago so not much better than yours.

[Trigger]

That style of tank was not on any UK 550's only the early 550 in the usa and Europe. It was originally for the CB500 and that has a two out let tap that will fit straight to 550 carbs with new fuel lines 

[matthewmosse]

But k3 from '78 if like my 2 will have 1 fuel line I think. Depends what is fitted - it is possible my k3s are / were mongrels. Point is check, then buy to suit what you have or be prepared to modify. The taps are not interchangable between k3 and the 500 tank. I have not a clue about F model 550s, only the 500/4 and 550k3 as these are what I have, being a tightwad over the years I have mixed bits up between these models to keep whatever was my daily transport running without expenditure. Everything off one of these will fit the other bike, but you may need to swap extra bits to make things work, eg, seat and tank best moved together to avoid cutting stuff or messing around, engine and clutch cable plus brakett etc. Often the ammout of changes mean that whilst yes a bit can be used it causes a few knock ons to the cosmetics that may hack off some owners to make them decide it isn't worth doing.

[Hudson.]

Ahh ok interesting thanks for the insight, I plan to have a different seat all together so it wouldnt matter in the long run, the standard seat will stay on there for now though. Quite like the raised fuel filler of the US tank then!

[matthewmosse]

I must agree the Us or cb500 tank is far nicer to look at. Probably worth the messing to get it fitted if the seat is due replacement anyway. Let us know how you get on, I will be interested in how it fits if you get the other tank shape - it is one thing knowing I cobbled up something I barely remember years ago, and quite another if you ( or we) can identify the bits concerned.

[Menno]

I just checked and here is what I've found:

A 500 tank (k0 or k2 doesn't matter) will fit on a cb550 frame with no problems.
However, the seat will have to be adjusted. Or else there will be a gap between the 550 seat and the 500 tank.
If you have a 500 seat it will most likely fit the 550 frame as well and solve the gap problem.

The fuelcocks are a different problem. There are at least 3 different fuelcocks used on both the 500 as with the 550 tank.
(2 different ones on the 500 and two different ones on the 550)
If you use a 500 fuelcock you simply need a T piece to lead the two hoses into one. Or block up one of the hoses with a screw in the rubberhose.


Ok, last very important thing: the fuelcock attachments differ a lot. They might look the same but there are lots of differences. I will try to put up some pictures...

[Menno]

So the first is from a 500 k0 or k1. It will also fit the early Honda cb 750 and 350 although the outlet is different - the base is the same.
The second is From the 500 k2. If I'm correct it will also fit the 550 k1 and the late cb 750 till k6. It will also fit the 750f2 but not the f1. And the 400.
The third is from a 550 k2. It will also fit the 750 k (after k6) although nr 4 is correct for the cbc750 k. It wil also fit the cb 750 f1.

Questions?

[Menno]

A cb 500 k1 tank on a cb550 frame:

[Menno]

Her you'll see the differences..

[Menno]

Sorry, a bit chaotic.
Still trying to get the hang of this forum...
 

[Trigger]

Nice to see you on the forum Menno. Great bit of tank information.