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Is the main differences the intake porting size? Also is the intake boots mounting holes the same? And is this the same between 400 and 450?

Thanks in advance.
 

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Combustion chamber differences also. Basically it looks the same and that's the end of useful similarities. Can't use an A head on a manual and can't use a manual head on an A. Yes, it'll bolt up and you'll be able to get it to run but there's a big loss of power.
 

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Whats the cause of the power loss? Is it due to having lower compression? Just curios...This stems from me asking about the 450 jugs and heads swapping into a CB400A and you had said to use the 450A stuff due to power loss with the non A parts and it got me to wondering the difference in them.
 

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The difference is in the velocity of the intake, smaller ports equal higher velocity for better filling of the chamber. Combined with the A model flat top pistons it makes a difference in torque which is what the A model needs. Manuals work better from HP vs. torque since there's more gears
 
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