jetworks ported cylinder

[rowand44]

I picked this jetworks ported cylinder up off my buddy. I had the chance to ride his ski with this cylnder on it and it hit great down low.While going over it I noticed a trench in the top of the exhuast side.i haven't seen that before. does anyone know the reasoning behind this?
Thanks!

 

[Big Kahuna]

I will take a wild shot and could be totally wrong....... I am guessing it is to help scavenge the last the burnt charge. As the piston is coming down it would help to start to pull that charge out..........

 

[erik mx45]

jetworks is doing mine as a right this i will ask him !see if comes on mine!

 

[rowand44]

Thanks guys.

 

[Glifxxsj]

Eric post pictures of your new ported cyclinder when you get it.

 

[erik mx45]

ok should be here next week just talked to jw yesterday almost done !

 

[erik mx45]

parts should be here few days jw shipped out thursday!

 

[88kawi5fiddy]

starts exhaust blowdown duration earlier w/o eating the rings too bad.

 

[erik mx45]

my ported cylinder i got back did not have this from jw !

 

[Big Kahuna]

Depending on the intended use the porting could be different.

 

[rowand44]

Erik did you get your cylinder ported for freestyle use?

 

[erik mx45]

yes sir freestyle! or freeride got it running today it feels real snappy goes to high rpm real quick!and not tuned yet cant waite to hit water!

 

[Dartman]

i have seen this on some maxed out motocross cylinders...think it was for high compression engines to have easier starting

 

[88kawi5fiddy]

cylinder wall scallops are different. they allow for easier starting. this starts the initial blowdown timing to start earlier increasing transfer duration potential. i.e. - reduces cylinder pressure earlier allowing more air from the bottom end to fill the cylinder from the boost and transfer ports.