I've been looking at my honda blackbird carbs and the two middle carbs have longer ram pipes than the outside two. Looking through various motorbike manuals it seems that other honda bikes also have this feature (cbr400 for one). I am more curious than anything else as to why this is the case. I seem to remember someone saying something about them but can't remember what it was.

anyone got any ideas ?

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I seem to remember someone saying something about them but can't remember what it was.

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There's one theory that I have (which may be untrue but will certainly work!) which I have applied to exhausts in the past as well.

The pulse tuning of the intake lengths is conventionally set together, with all equal lengths, which then makes the intakes come into their tuned range at the same point in the rpm range, giving a lift in power.

If the intakes are different lengths, different cylinders will hit their tuned rpm at different points when revving the engine though it's working rev range.

Quite possibly Honda have used this to widen the power band of the engine and make it less peaky.

The same can be done for exhausts, making the tuned lengths different between 1-4 and 2-3, which enhances the torque spread of the engine.