Adler exhaust design.
Article from Phil Irvings book, Automobile Engine Tuning,
published in 1962.
Click on the image to enlarge it.
Some improvement to top end power can be made by
restricting the discharge of exhaust gases from the
mufflers. A generic 40mm brass welch plug with a 19mm
hole drilled through its centre can be inserted
into the end of a typical after-market muffler and
pop rivetted into place. Don't go below this hole
size or you will lose so much power in midrange
that the bike will not be able to hold 4th gear
on hills.
