Topic: CB400 Engine Swap

[Jamiez]

Hi, I have a 78 CB400 rolling frame and a 80 CB650 engine im looking to put in the frame.  I know that its not a direct bolt in.  Im sure someone has done this before.  Is the cb 400 frame worth using?

Thanks

Jamie

[phil71]

This swap will require violating laws of physics.

[Jamiez]

That doesnt sound good.

[Bodi]

The 650 engine is quite a bit higher than the 400F, and the CB400F uses a cradle frame with almost zero clearance above the engine. The 650 is also longer... same sort of issue.
Not necessarily a law of physics, but it's generally accepted that two solid objects can not occupy the same space at the same time. I would find a 650 frame somewhere, in my opinion using a 400 frame would require rather too much cutting and stretching to make it worthwhile. And you'd have many more issues with chain alignment etc.

[crazypj]

Bit of cutting and welding and it could be done, probably not a smart idea as 400 frame is barely capable of containing the weight and power of original motor (and flexes like crazy if you start 'pushing' things with a 466 or 490)

[Jamiez]

Ya i knew id have to build a cradle of some sort and make new engine mounts but if your saying the frame is just not heavy duty enough theres no point.  Theres a guy selling a 80 cb650 in my area for $200 bucks.  Sounds like the route to go.

Thanks