| If you read Moto-One Performance notebook it would seem quite important - I've been looking into this myself with a view to making a better set of downpipes and collector for my 800 race bike.
I think the 620 has a 40mm diameter pipe like my 800ss', dropping below this seems to affect power adversely if Moto-One's experiences are anything to go by when they were playing with the 750ssie. If you do make pipes then it's important that you ensure they do not restrict the flow of gases exiting the exhaust ports. |