Header or primary explanation

[mountain80]

Hi all doin some reading as I built a new stainless exhaust flange with a custom formed pipe(built the forming tool that makes the first part form the exhaust part square and the other half continues round as 1'' stainless tubing 0.0625 wall its all i had). Wanted to get a better flow.

Anyhow my main question is "primary" or header length I have read is a good start at around 12''. I have a SBP exhaust and want to know:

Is this measurement form the edge of the cylinder or piston to start with?
Does the measurement end at where it slips in to the second section(the main pipe itself) or where the main pipe starts to increase in diameter(taper).

It is not totally clear so if anyone can give me concise info it is appreciated.

Cheers.

 

[fx-2]

This might help .http://www.dragonfly75.com/motorbike/index.html . Have fun reading . Hope it helps Dan

 

[Ghost0]

Well to save some time reading I can give you the basics. When we reference the the 12 inches we are talking from the exhaust gasket to where the expansion chamber starts to expand. However, the technically correct way to measure the prechamber length of a tuned pipe is taken from the exhaust port where the piston interfaces with it to where the expansion chamber starts to expand. We just try and simplify it by using the exhaust gasket which everyone knows where it is and have adjusted accordingly. So really the length would be 13 inches if you take into consideration the approximate 1 inch from the exhaust port to the exhaust gasket. Anyway I would start at 13 inches because you can always shorten it.

 

[mountain80]

Thanks Ghost I got er done now. Btw is there packing in the SBP pipe from the factory?? It seems to be getting louder maybe its me but I was considering drilling out the endcap rivets and repacking it, i thought about using stainless steel wool/pot scrubbers. Any info is appreciated.