Most of the smaller Honda twins are 180 degree, which is why they sound so... strange. Some were built in both 180 (CB) and 360 (CL, where broad power band is more important).
H-D is 45, Indian is 42, etc. Some JAP 50.
The missing factor in firing and rotational order is crank-pin position. Even with a common (side-by-side) pin, offsetting the centerline will offset the firing order, which is either added or subtracted (duh) to the cylinder position (odd-fire Buick V6, etc.). Needless to say, many more combinations can be built than will run. The Yamaha XS650 (originally an A65 variant with 360) crank can be re-timed by simply re-indexing the splined connecting shaft between the L & R flywheel halves:
http://www.650motorcycles.com/XS277kit.html
H-D is 45, Indian is 42, etc. Some JAP 50.
The missing factor in firing and rotational order is crank-pin position. Even with a common (side-by-side) pin, offsetting the centerline will offset the firing order, which is either added or subtracted (duh) to the cylinder position (odd-fire Buick V6, etc.). Needless to say, many more combinations can be built than will run. The Yamaha XS650 (originally an A65 variant with 360) crank can be re-timed by simply re-indexing the splined connecting shaft between the L & R flywheel halves:
http://www.650motorcycles.com/XS277kit.html
