cb 400 N motor into cb 250 T frame

[fester]

hey all
dose any one know if a cb400 twin fit into a cb250 frame or can i swapthe barrels and pistons and head from the 400 onto the 250 ,are the bottem ends the same ?????????????
cheers
fester

 

[barnicle]

first; you are talking mid 70's cbs?
I have heard that the 250 and 360 have interchangeble parts, same frame, but I dont know about the 400. do you already have the 400 motor? if so search for info on 360/ 400 swaps as well. if the 360/400 works the 250/400 should as well. if you don't have the engine yet, you might consider a 360. I really like them and they are surprisingly fast bikes.

 

[fester]

the 250 is a 1980 mod and the 400 is the N mod 82 i think .. thank s just the same but a mate from wa has told me that it will fit

 

[Kanticoy]

Might fit the frame, measure front to back and bottom to top. new motor mounts will need to be made. The motor parts will not interchange.

 

[Maritime]

I think the 2 motors on these models are identical in dimensions, just displacement is different. the US and Canadian markets don't have the CB250's he has, it was an Aussie UK europe only model. But liek Kiley said. Just take so measurements in the key places. I can measure my 400 engine if you need me to.

Cheers

 

[Moo.]

Sorry to drag up a thread thats a little old, but i was wondering the same thing at the OP, wondered if he had tried anything?

Will the 400 barrels and piston work? As the 400 has a longer stroke.. so would it work with the 250 bottom end and stroke? Even though it would end up as only 323cc not 395cc

Cheers, Moo.

 

[crazypj]

Yes, it will 'work' if you really want a motor with 4.3:1 compression.
It isn't a simple thing to fit bigger cylinders without doing the crank, etc.
Need a new top engine mount for 400 into 250 (or 250 into 400) I have several for 400 laying about