CB400T & CM400E Engine Compatibility

cleeuw

cleeuw

Active Member
Anyone know off hand if the engines in a 78-81 CB400T and CM400E are identical? So far all I can tell is that the CM400E doesn't include the tach drive.

Going to look at one this weekend - wanted to get some feedback before I make the journey.
 
I'm not 100% sure but I think the cm400e has a single carb. But don't quote me on that. Some more experienced cm guys would be able to confirm or correct that. Otherwise they don't have a tach like you already mentioned.

Edit: Never mind I think they may have only had dual carbs.

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It's a twin, but the CM uses 30mm carbs (CB uses 32mm). Checked the HSM - should be okay for info, but sadly w/o an engine because I don't have the right carbs.
 
So your cb400 is missing its engine completely? Would be awesome to swap in a cb450 out cm450 twin. More cubes and I've heard they bolt right up.

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The motors are largely identical although it depends on the year. Prior to 1980, the carbs (both models had dual carbs) were 32mm. In 1980 it was dropped 30mm as part of a re-design that included the combustion chamber and keeping the EPA happy. In 1982 the bore was enlarged to make it a 450 but they kept the 30mm carbs. Apparently that hp is the same but you get more torque out of the 450.

The A models are a bit different from the others thanks to the torque converter in them. They also use 28mm carbs.
 
ponycarman said:
So your cb400 is missing its engine completely? Would be awesome to swap in a cb450 out cm450 twin. More cubes and I've heard they bolt right up.

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Click to expand...

I didn't know that - do you mean the 78-81 Rebel 450 engine?
 
I'm not sure about the rebel. But I know in the 80s they made cm450's and cb450's with the same frame. They both had the same engine but the cb's engine was a little more purdied up.

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The CB450 Nighthawk and Rebel are essentially the same engine except for a couple differences in the case.
 
Morgan said:
The motors are largely identical although it depends on the year. Prior to 1980, the carbs (both models had dual carbs) were 32mm. In 1980 it was dropped 30mm as part of a re-design that included the combustion chamber and keeping the EPA happy. In 1982 the bore was enlarged to make it a 450 but they kept the 30mm carbs. Apparently that hp is the same but you get more torque out of the 450.

The A models are a bit different from the others thanks to the torque converter in them. They also use 28mm carbs.
Click to expand...

Hmm. This is interesting because I bought the bike which is a 78, but with an 81 engine. Not sure if the PO changed the carbs. Would there be any problems running an 81 engine (designed for 30mm carbs) with 32 mm carbs? Or vice versa?
 
I really couldn't tell you how well different carb/motor combinations would work out. My Haynes manual lists carb model codes for 1980-83 in it. Looks like it should be a VB22 of some sort if the carbs match the motor. You can find the code stamped on the the carb but I forget where, on the side I think.
 
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