Winter is the time I browse through all my motorcycle mag back issues. One item I'm focused on is 3 to 4 inch aluminum intake manifolds on bikes as diverse as G50s, CB160s and my old Ducati 250 road racer. If theses manifolds are beneficial for these, why not our S40s?

https://www.ooracing.com/images/source/Carbs/carb-2.jpg
cheers!

I'm not really after anything other than knowledge.
What's the point of the big manifold?
My K&N is 4" long, so there is room there.

Zippy:

I believe that some form of "wave tuning" can be accomplished by adjusting the length of the intake manifold - same as it can for the exhaust side.  The theory/formulas are beyond my grease monkey approach to performance.

I am not sure about the stock carb - but the top of my Mikuni round slide carb would hit the top tube if I moved it backward...unless I moved it far enough back to get to the place where the tubes split (or you made the manifold with some curves in it.

The long manifolds on the little Honda engines allow the horizontal cylinder to work with a standard vertical carb.  I suppose the Harley Sprint had to do something similar.

I really like the Matchless you linked......classic looking big single!

A G50 is a rolling piece of artwork,pure and simple,motorcycle porn !

Verslagen ,myself and a few others , have tuned intakes , how do you think my stock bike ,except for a stock Dyna muffler ,has a top speed of 90 mph, and an est. 33hp?

  Tuneing your intake-6/30/16@ 18:51

Look at the Matchless again,  it's not so much the carb spacer (though the carb in the middle is ideal) but the total length of the intake between the filter and the intake valve.