The stock main jet size on our Bonneville Americas was 110.Not 120, not 122, but
110.
I speak from the perspective of a pre-fire bonneville america.
Check out this link to tJP's
Tuning Notes for the Triumph Bonneville Family of Motosickles page 10.
Look in your manual at the specs page.
And furthermore the header pipes are NOT stainless steel.
