SOHC.co.uk Forums > CB350/400

400 into 350 swap?

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gtmdriver:
I have a CB350F with a tired engine. There is a lot of blowby and crankcase pressurisation.
I want to rebuild the 350 engine but here in the UK spares are rare and it make take some time.
To avoid the bike being off the road I would like to temporarily fit the complete engine from a CB400F.
Apart from the clutch operation are there any other differences?
My bike has the full 4 pipe system. Will that couple up to the engine OK?

Orcade-Ian:
I have both the 350 and 400, as you say the clutch operation is different but as mainframes are the same, I can’t see why you can’t couple the cable in the normal way- you might have a problem with cable lengths though.  The 400 clutch cover doesn’t fit the 350 cases but you don’t need to change any of that.  The gearchange is different and 6 speed on the 400.  Not near my bikes till tomorrow but I have a feeling the 350 lever works t’other way - I’ll check.  As the stroke length is the same on both and only the bores are different, I would guess that the pipes would fit without drama.
Can’t think of any other problems you might meet.

Ian

Just spotted that was post 333 for me - spooky, that’s the model number of the CB350F -  Off to buy a lottery ticket🤓

Orcade-Ian:
I was wrong (again) the gear-lever has a linkage on the 400 but straight on the shaft on the 350, so that will not be a problem.  Difficult to measure accurately but the exhaust ports are close to the same height from the lower frame rails on both bikes - go for it!

Ian

gtmdriver:
Thanks for that.

On the US site they talk about footrests kickstarter and brake lever too but nothing insurmountable.

Orcade-Ian:
Yes the 400 footrests are different but you are using the 350 pegs so if you fit the 350 gear-lever to the 400 box, I can’t see a problem. The only issue might be that your right hand 350 footpeg might be too close to the 400 clutch cover - might need a spacer and longer through-bolt.  Kick start shouldn’t be a problem as your footrest is in front of it rather than behind.  Brake lever is already longer to match up with the footrest.

Ian

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