Author Topic: 1978 CB550 fuel line(s) (Read 10198 times)

beelsamin · « **on:** July 26, 2008, 12:24:14 pm »

Does the 78 cb550 have 2 gas lines going to the petcock? It looks like the PO put a petcock on the tank with only one outlet.
Thanks

Deltarider · « **Reply #1 on:** July 26, 2008, 12:30:13 pm »

Quote

Does the 78 cb550 have 2 gas lines going to the petcock?

No. Look for a joint.

Quote

It looks like the PO put a petcock on the tank with only one outlet.

The K3/K4 originally had indeed only one outlet. Look for that joint somewhere under the tank.

beelsamin · « **Reply #2 on:** July 26, 2008, 12:35:34 pm »

Joint? Do you mean a T connector?
There is a clear hose running from the tank to a fuel filter then to one of the carbs,another carb has a hose coming out of it not attached to anything.

Spikeybike · « **Reply #3 on:** July 26, 2008, 12:59:41 pm »

you need to make a tee , so gas goes to that other hose

beelsamin · « **Reply #4 on:** July 26, 2008, 01:07:25 pm »

I am looking at the honda microfiche for the 78 cb550 it shows a straight joint between two pieces of hose but no T. ARRRGGGHHH,and does not show where the hose connects to the carbs.

Deltarider · « **Reply #5 on:** July 26, 2008, 01:22:03 pm »

Quote

I am looking at the honda microfiche for the 78 cb550 it shows a straight joint between two pieces of hose but no T.

That's the tank drain tube. Look on another page

Deltarider · « **Reply #6 on:** July 26, 2008, 01:31:18 pm »

Strange... I can't find it either, not in the original parts list. Very strange. I try to remember if the K3/K4 had only one feed line...

ieism · « **Reply #7 on:** July 26, 2008, 02:06:57 pm »

Do you have a K3 ?

What are the numbers on your carb?

My 550K3 only has a single fuel line. Are you sure there are two connections for a fuel line on the carb? Mine only has one. If I remember correctly the carbnumber is pb46a...

And these carbs are not like the ones you see in the manual .

beelsamin · « **Reply #8 on:** July 26, 2008, 03:11:37 pm »

I have a 1978 Cb550K. The main fuel line goes to the number one carb on the left (facing toward the handle bars) the loose fuel line which is a smaller diameter comes off the top side of the left side number 2 carb and this line goes where?

ieism · « **Reply #9 on:** July 26, 2008, 03:46:39 pm »

That's not a fuel line then. You sure it's not an vent or overflow tube or something?

It wouldn't make sense to make one fuelline smaller in diameter than the other.

Plus, on the other 550 carbs with two fuel lines, it doesn't go to the first and second carb either. And they mount in the same place on the carbs too, and look the same.

My guess is you have only one fuelline like my K3.

TwoTired · « **Reply #10 on:** July 26, 2008, 03:48:59 pm »

The 77-78 K model CB550s had a single outlet petcock and a single inlet carb nipple to feed the whole bank of PD style carbs.
There is a smaller nipple nearby for fitting a bowl vent hose on the PD carbs.

Earlier style carbs had two inlet nipples and two outlet petcocks,

There is also a transition era where a one outlet petcock went to a "T" so the that both the nipples on the earlier carb style were fed.

Cheers,

beelsamin · « **Reply #11 on:** July 27, 2008, 07:02:18 am »

So the smaller 6" tube coming off the #2 carb would be a vent? The bike has had 3 PO's and it shows so I'm really finding it difficult to find the original setup from the rocket science they were using

They drain hoses from the bottom of the bowls,were they 4 seperate hoses as shown in the honda fiches ? the carbs now have 2 hoses,carb 1 goes to carb 2 and carb 3 goes to carb 4.
thanks

Spikeybike · « **Reply #12 on:** July 27, 2008, 09:08:39 am »

there should be 4 separate drain hoses.

TwoTired · « **Reply #13 on:** July 27, 2008, 10:40:42 am »

Quote from: beelsamin on July 27, 2008, 07:02:18 am

So the smaller 6" tube coming off the #2 carb would be a vent? The bike has had 3 PO's and it shows so I'm really finding it difficult to find the original setup from the rocket science they were using
They drain hoses from the bottom of the bowls,were they 4 seperate hoses as shown in the honda fiches ? the carbs now have 2 hoses,carb 1 goes to carb 2 and carb 3 goes to carb 4.
thanks

The smaller six inch tube ought to be long enough to route back behind the engine case and in front of the swing arm.

The nipples at the bottom of the carb bowls are over flow drains. Connecting to other carbs defeats their purpose and overflow will go to the engine cylinders and contaminate the engine oil. If your oil smells like gas, you now know why.

Theres are meant to be 4 individual hoses that route back behind the engine case and in front of the swing arm.

Why haven't you asked about the engine breather hose, I wonder? Or, the gas tank well drain hose? These are also popular questions, found in the forums.

Cheers,

Accolay · « **Reply #14 on:** July 29, 2008, 06:34:12 pm »

What? Drains on the bottom of the carbs? Oh, so that's what should be on those nipples!

cbass*gxc · « **Reply #15 on:** July 30, 2008, 07:54:42 am »

If you look at the carbs #2 has 2 nipples coming off the carb for hoses. The one towards the back that is bigger is for the fuel line and the smaller one in front of it is for the vent line. Like TT said the nipples on the bottom of each carb are drain hoses for the float bowls.

jason teamshralp · « **Reply #16 on:** August 07, 2008, 01:00:36 am »

anyone know the bung diameter of the 78 cb550 petcock bung? I'm going to replace mine but can't find the size anywhere. is it 22mm?

TwoTired · « **Reply #17 on:** August 07, 2008, 01:32:08 am »

78 tank bung is 5/8".

jason teamshralp · « **Reply #18 on:** August 07, 2008, 09:29:53 am »

thanks TT.
Would this one work? http://www.z1enterprises.com/detail.aspx?ID=1745
or would you recommend going with something else?

TwoTired · « **Reply #19 on:** August 07, 2008, 10:15:36 am »

Something else.
A 5/8 bung converts to 15.875mm.

Cheers,

jason teamshralp · « **Reply #20 on:** August 08, 2008, 12:47:15 am »

okay so I have been looking for a petcock that will work for the last three days or so.

Has anyone bought a replacement one and had it work?
Everywhere I call/look says that the 78 cb550k petcock is discontinued and no one knows what size will fit for sure.

TwoTired · « **Reply #21 on:** August 08, 2008, 12:51:36 am »

A cx500 petcock will fit the bung. But, the outlet points in a different direction.

jason teamshralp · « **Reply #22 on:** August 08, 2008, 05:29:48 pm »

thanks i found one at a salvage place that had a new one in the plastic. works great. now on to my constant oil leak...

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Author Topic: 1978 CB550 fuel line(s) (Read 10198 times)