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1981 CM400T
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Discussion Starter · #1 ·
So,
seems my tank has few pinholes and I'm pretty sure it's gonna spread..
welded few spots but keeps spreading..cannot detect from where exactly..more like "fuel moisture" than seeping..
the rag gets moisted when put underneath..not wet though

I found a tank from a cm185 model for a decent price (some 50$), seems like new inside/outside
but since i cannot phisically check it, the guy is willing to mail me
does anyone know if it fits a cm400t 1981 model?

thanks
cheers
t
 

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1981 CM400T
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85 Posts
Discussion Starter · #2 ·
Update:asked the guy to measure it for me,the mounting ears on a 185 tank are waaay narrower , cca 9cm against 15cm on the cm400t...biggest issue i suppose is the tunnel - also narrower and i guess requires a lot of beating to make it fit...so all in all no point...the rear mount could be an easy fit i guess,,,,
 

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1981 CM400T
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85 Posts
Discussion Starter · #4 ·
Hi, got the tank from a 185 twin, will measure it alltogether this week and will post info and pics in case someone needs it..however, seems it can be fitted on a cm400 without some significant mods...
 

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That would be great to have the info, especially the mods needed. That way people may be able to fit a 400 tank to a 185/200
 

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1981 CM400T
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85 Posts
Discussion Starter · #6 ·
Ok so these information will not be 100% precise
as the measurements were made in about half an hour just to determine whether it fits or not..detailed ones will be made when/if the tank change will occur...
the biggest concern was the tunnel of the tanks which seems on both tanks of pretty same width, and seems to lay good onto the frame - and only that really matters,,
even if the cm185 tank seller swears the two frames were identical, wouldn't bet on it, the cm185 must be somehow smaller/narrower
the conclusion is the tank of the cm185 twin can be fitted onto cm400 with few mods, front slide adapters and rear side bracket to be added
(on the other hand, not sure if the cm400 tank can be put onto the cm185 as is cca 7 cm longer (at least the one I have) so there is a chance that is too long,
I would say it is NOT interchangeable)
IMG_3560 (2).JPG
So I'm going to spit&shine it a bit and repaint it in actual colour...it's mirror looking inside looks like new,,
the greenish one in photos is a cm400 i have on it now, and the grey one is of a 185 I acquired
IMG_3564.JPG

Frame neck width is 6,02 cm, and 12,61 cm at the mounting studs where the rubber slides go (each stud length 3,3 cm cca)..
IMG_3575.JPG
IMG_3573.JPG

The first thing to notice is that the distance between the mounting ears on a cm400 tank is 14-15 cm, and on a 185 9,6 only (6,5 cm between the very ears)...
between ears.jpg
so when put onto the frame, it barely enters the frame by the ears and you cannot slide it in as the studs are way wider than actual tank mounting width,
some stud shortening is needed...leaving hardly lets say 1,8 cm of each stud on the frame in this case...rubber slide of the 185 is 1,94 cm so needs some cutting too..
you could for instance drill 2 more studs extra for this 2 cm somewhere lower, and leaving the original studs intact once you want/need to go back..that way it could possibly align with the rear mount hole
maybe this is a better option as the cm400 rubber slides are 4,3 cm so the 1,8 cm stud is not that assuring though to be mounted on
IMG_3568.JPG
IMG_3569.JPG
IMG_3570.JPG
IMG_3572.JPG
OR you can drill a 3 cm long screw in the 1,8 stud and still can return to the original specs
OR you can put an oval rubber grommet let's say 7 cm x 3,28 and fix it like that - should be stiff enough
IMG_3583.JPG
so few options available - important thing is it can be done - I like the tank to be secured well in place so I'll see what is safest first!

NExt thing you notice, is the big gap in front which the 185 tank leaves when seated onto the frame, the 400 tank seats fully leaving no gap whatsoever....
see comparision photo below with front 2 tanks and tank mounted - a big void noticeable
(but looking at photos on the net, all 185s have this gap in front, it's normal, it's not only for beeing put onto 400 frame..don't know what is for but it does not look very good :/)
IMG_3561.JPG
IMG_3565.JPG
IMG_3576.JPG

Last thing is the rear mount, as 5-6 cm shorter than the cm400, the tank needs a bracket to be mounted/fixed on,
that's not the problem , it can be designed after deciding how to make the front mount
IMG_3562.JPG
IMG_3506.JPG


The tunnel width is ok, lays ok on the frame, the front slides can be fitted in few ways, rear bracket should be the last thing to be worried about
The petcock is the same I recon and doesn't seem to interfere with cyl head/carbs
so all in all, can be done if needed!

I guess not the best option but should work fine..original is always better of course
but when you are limited with parts like I am, that's a fair alternative
I hope this helps someone who in doubt
especially the cm185t owners who think of getting a bigger cm400 tank..
 

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Nice explanation of everything you've encountered with this. As you said it's an alternative that will do in a pinch if needed.
 
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