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Hi, I have a 1971 Honda CL 350 that we had running two years ago until we blew a hole in the cylinder. I want to rebore it but am also looking into buying a working engine. I am able to get a CB 450 engine. Will that fit in the CL 350 frame? I know the CB and CL are the same but is the 450 exterier larger then the 350 and too big to fit in the 350 frame? Thanks
 

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So someone told me the exterier dimensions of the engine are the same and that it should be the exact fit. Does that make sense? Do the companies sometimes make different cc engines with the same exterier engine shell?
 

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Only if it is the same basic engine. But that is very rare. I can not think of any. Maybe the newer Honda Shadow, and some three cylinder modern Triumphs. The 350 and 450 engines are a lot different.

UK
 

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Ok, what I probably will do is have him bring the engine and I can look by eye and see if it is the same basic engine. If it looks to be the same exact thing then chances are the engine mounts will probably match up.
 

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The engines are constructed very differently, but IIRC the bike frames themselves are pretty similar. I would be surprised though if it was a direct swap.
 

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Is that for a 71 CB engine. Can you find one for the 71 CB 350 also, I couldn't find that diagram.
All the CB450 engines have the same mounting points; the only differences are between the K0 (65-66) and later models. The bottom bolts are a somewhat smaller diameter, and the casting for the front mounts is wider in the K0. BTW, a 71 would probably be a K4. Honda K number assignments went by serial number, while the registered date was when it was sold, so there can be an overlap of K number vs date, IOW, a bike with a K3 S/N could be registered as a '71, just because it hung around the dealer longer.

That drawing is from the service manual; I don't have one for the 350, but I'm sure you can find a copy on line somewhere.
 
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