While searching the net.....

[gsxr400 racer]

Isnt it true that a rain drop hits terminal velocity faster than anything else???

[Herr Tod]

Makes me wonder. It looks like he's filled in the bottom of the port to level it, but that would reduce swirl. Or he's trying to improve flow on the port floor, where the flow starts as the inlet valve opens, thus contributing a lot to the total flow when the valve is fully open. The only thing that should be done with the wedge between the inlet valves is cut it back to align with the port walls and round it off. Knife edging something is good for cutting, not flowing gas. The inlet charge needs guiding, not cutting.

[97af]

 It's not uncommon to design some tubulence in to help promote complete combustion... but that not usually something the average shade tree howler monkey can do in his garage.

 

[Chris H]

This may be true but we are talking about a fuel rich air mixture that is drawn into the engine due to low pressure at the valve openning, this happens at a very high speed for a very short time and if the edge is too wide then the fuel will be deposited onto the inlet wall, have you ever seen a race tuned reedblock from a two stroke. Also the pictures d'nt seem to match the first has the edge taken to a knife and clearly has a brass drilling, the others that have been filled do not have the drilling and apart from the filler are very stock showing casting marks etc, BUT anyone having a go at makin their bike faster is tops in my book.
Get your dremmils out lads!!!