Topic: are these cb750k sohc exhaust pipes (solved)

[setdog]

hello, need a bit of expertise to help me sort this out.

i have a 78 cb750k cylinder head, and i came into possession of these exhaust pipes.
they seem to fit into the ports ok(?), but the exhaust flanges and the collar (or whats left of the collar)
that came along with them do not seem to fit at all.

based on what i can tell, these flanges (and the collar) might be for a 79 DOHC CB750.

which leaves the question of whether i can still take advantage of these pipes in a 78 cb750 k8 head,
if i use correct flanges and collars. 

this build is a low budget jalopy resurrection that started with a bare 73 frame. the goal is to simple get it operational, so while these pipes might be hard for some of you to look at, i hoped i could just wrap them up and enjoy some old 4 into 2 slash cut pipes. Even if my neighbors won't.   

[BenelliSEI]

I have a ‘78 and agree the finned, chrome collars don’t look quite right, but if they fit over the flared end of the pipe, and slide down on the studs, why wouldn’t they work? They rarely get bolted right down to the stud base on the head. If you use a new copper gasket (the one like a big O ring) under the pipe, then side in two of the 1/2 collars, do they Seat well in the chrome collars? You’ll need 8 of the 1/2 collars.......

The pictures aren’t too clear, so I may be misssing something?

[Don R]

 Be sure the inserts are turned the right way.

[Dolomite]

My 78K has those style exhaust clamps, they only fit one way so try rotating 180* if they don't line up correctly. With the 1/2 collar and copper gasket underneath.

[BenelliSEI]

The other reason the fins are stepped on the chrome collars is to clear the frame down tubes on #1 and #4........

[setdog]

here are some additional pics

hopefully one shows more clearly the gap between the flange and the exhaust port,
the other hopefully shows the gap between the pipe and the flange.

i dont see how these could possibly be from a 78 cb750K as stated.

additionally the pipes seem to be a smaller diameter, but the end of the pipe does fit squarely into the
opening where the copper gaskets seat.  oh and now im worried about them fitting past the kick stand and
being able to actuate the gear lever without interference

ill see if i cant get some 78 k parts to fiddle with over the wknd

[Bankerdanny]

Where are the rest of the 2 piece sleeves that fit inside the finned collar? I see one in your photo, there should be 8, 2 per pipe.

Those fit snuggly over the pipe, long side towards the head. Then the finned collar slides over that and onto the studs. The finned collar won't go all the way to the head when it is tightened.

[setdog]

Where are the rest of the 2 piece sleeves that fit inside the finned collar? I see one in your photo, there should be 8, 2 per pipe.

Those fit snuggly over the pipe, long side towards the head. Then the finned collar slides over that and onto the studs. The finned collar won't go all the way to the head when it is tightened.

i only have 1 of 8.  and it appears to match exactly oem part number 18233-438-000, which i believe is 79-82 dohc. 
even tho i only have the one, the gap seems too big you can see it in one of these pics

ugh...i feel like ive been bamboozled

you can also see how well the end of pipe fits into the port

mind you, i never expected oem, but if they "came off a 78 cb750k" i would expect to be feeling more confident at this stage

[Bankerdanny]

The gap is big because there is supposed to be a 2nd half of the sleeve.

[bryanj]

The finned clamp goes on the pipe first then fit the pipe into the head port, with a gasket, two half round clamps, with the lip towards the clamp,  then hold the pipe in when finned clamp is done up. Picture in parts book shows it all

[onepieceatatime]

Those are definitely DOHC style finned flanges. The fins on one side being so much larger is the give away. The '77 and '78 SOHC CB750K and I think the '76 CB750F flanges were the same type, with the split collars, but the fins were more even.

[BenelliSEI]

Agreed...... ‘77 and ‘78 chrome fins are stepped, but only slightly.

[setdog]

pretty sure i figured out my situation and have a solution.

the  flanges (with the long fins) i got are most certainly DOHC.
the pipes are idk what they are.

picture tells all.

the second pic is my solution, an RC Engineering 4 into 1. 
i dont have to pull the exhaust studs on the head do I?  any reason i cant
just use nuts to secure them?  there is alot of rust, a small hole near the collector and
about a walnut sized hole under the megaphone, but i think i can easily
deal with those.

[754]

Yeah just nuts, try acorn nuts if you can get them..May need spacers.