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Discussion Starter · #1 ·
I found this in a 1986 Chilton manual. These are all interchangeable to the best of my knowledge. These are total gallons including reserve


2.6 gallon w/.45 reserve 1981 CB/CM 400 T & CM 400 A


2.6 gallon w/.8 reserve 1979-80 CM 400 T


3.2 gallon w/.5 reserve CB 450 SC


3.4 gallon w/.5 reserve CM 450 A/C/E & CB 450 T


3.4 gallon w/.75 reserve 1978-80 CB 400 T type 2 & CB 400 A


3.4 gallon w/.8 reserve 1981 CB/CM 400 T


3.7 gallon w/.8 reserve 1978-80 CB 400 T type 1


3.8 gallon w/.9 reserve 1980-81 CM 400 C/E


As noted in the following post, there is a minor issue with seat fitment between CB's and CM's. There is either a gap or too tight. A little mod of adding or subtracting foam from the front of the seat solves it however.
10-15-13: The CM tank is longer than the CB so the rear mount doesn't line up, bracket needed. The CM tank is wider in front so the mounting studs need to be lengthen
New information 12-21-13 There are 2 frames for the 400 series, One for the 80/81 E model and one for everything else. The E model apparently is narrower at the fuel tank pucks and the rear mount back an 1" or so
 

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Nice to know. I also believe they are "interchangeable" but a CM tank won't mate up properly with a CB seat and vice versa. Any of the tanks should mate up with any of the frames.
 

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Discussion Starter · #3 ·
J-T said:
Nice to know. I also believe they are "interchangeable" but a CM tank won't mate up properly with a CB seat and vice versa. Any of the tanks should mate up with any of the frames.
Very correct there. I forgot to add that caveat.
 

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Discussion Starter · #5 ·
kj4130 said:
So I should be able to swap this style tank and seat...



In place of this style?

I beleive so, however! I don't know how the seat locks down on the 2nd. Also the side covers that blend into the tank may have different mounting tabs or locations. Then there's the rear fender area and tail light. Should be an interesting exercise that hopefully will work out for you.
 

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I believe it's the petcock that determines the amount of reserve. The length of the tube extended up into the tank is the important factor, as far as I can see.
 

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Discussion Starter · #7 ·
joemac said:
I believe it's the petcock that determines the amount of reserve. The length of the tube extended up into the tank is the important factor, as far as I can see.
Yes, that it the only thing that determines reserve. Remove it completely and you have no reserve. I like @ 3/4 gallon which let's me run quite aways but still gives me enough when it hits reserve to find more fuel.
 

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kj4130 said:
So I should be able to swap this style tank and seat...



In place of this style?

Why would you want to though, the back end would look odd and that older style ( we called in a Dream over here) is much nicer than the other ( which we had as a Superdream) well I think so. I really wish I'd bought myself a dream back when I could have done, maybe one will come my way one day.
 

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Discussion Starter · #13 ·
sorry to bring up an old topic but im wondering if anyone knows if any of the smaller nighthawk tanks are interchangeable with the cb400?
As far as I know all of the Nighthawks have a bolt on tank for the front mounting instead of the slide on pucks
 

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I was curious if anyone may know what kinda fitment issues, if any, i may have with a cb200/350 tank going onto a cb200t?
 

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What is a CB200/350 tank?.... The CB200 tank will fit the CB200T....Same/same....
 

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crap, i meant to say will a cb200/350 tank fit on a CM200
 

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Can't answer since I never heard of a CB200/350....
I've never tried fitting either a CB200 tank, OR a CB350 tank (Which I'm assuming is what you meant) on any CM200 model so I can't verify fitment .........
 

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Yes i meant a cb200 or cb350...i assumed the / would have implied that. but anyway, thanks!
 

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I found this in a 1986 Chilton manual. These are all interchangeable to the best of my knowledge. These are total gallons including reserve


2.6 gallon w/.45 reserve 1981 CB/CM 400 T & CM 400 A


2.6 gallon w/.8 reserve 1979-80 CM 400 T


3.2 gallon w/.5 reserve CB 450 SC


3.4 gallon w/.5 reserve CM 450 A/C/E & CB 450 T


3.4 gallon w/.75 reserve 1978-80 CB 400 T type 2 & CB 400 A


3.4 gallon w/.8 reserve 1981 CB/CM 400 T


3.7 gallon w/.8 reserve 1978-80 CB 400 T type 1


3.8 gallon w/.9 reserve 1980-81 CM 400 C/E


As noted in the following post, there is a minor issue with seat fitment between CB's and CM's. There is either a gap or too tight. A little mod of adding or subtracting foam from the front of the seat solves it however.
10-15-13: The CM tank is longer than the CB so the rear mount doesn't line up, bracket needed. The CM tank is wider in front so the mounting studs need to be lengthen
New information 12-21-13 There are 2 frames for the 400 series, One for the 80/81 E model and one for everything else. The E model apparently is narrower at the fuel tank pucks and the rear mount back an 1" or so
Bumping this thread as I'm looking to upgrade my 1981 CM400A tank, was looking at this tank here

Honda CM400T 1981 Gas Tank | eBay

However it seems (and this is judging by photo only) that it's not significantly bigger, not enough to put in the time/cost to make the change. Has anyone switched up a CM400 tank to something larger, say an older CB tank successfully?
 

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Discussion Starter · #20 ·
Any CM tank will directly swap to your A model and the seat will fit correctly. I would look at the larger 3.8 gallon ones. I also would not buy a tank that can't be opened, like the one listed, for pictures of the inside. Lots of old rusty tanks out there.
 
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