Found my 78 book. These are the relevant pages.

 … will create and upload as pdf …

Service News from 1971. XS1 XS1B XS2.

262 … exhaust pipe obstruction

264 … yamaha sealants

267 … XS1B ignition timing change

272/1 … universal crankshaft installation tool

272/2 … universal crankshaft installation tool

272/3 … universal crankshaft installation tool

275 … XS1 XS1B cylinder sleeve installation

278 … XS2 disc brake lever adjustment

281/1 … XS2 battery cable setup

281/2 … cable routing – tacho, speedo

283/1 … XS2 frame and engine nrs

283/2 … XS2 paint codes

285/1 … XS1 XS1B XS2 primary drive lash

285/2 … XS1 XS1B XS2 primary drive lash

 

 … will create and upload as pdf …