Yamaha SR400 2010-2021 Service Manual

Wikipedia's own account confirms this is genuinely the final chapter of an extraordinary production run: "Yamaha has marketed the SR400 in the JDM since model year 1978, with a production hiatus for model years 2008–2009. Beginning with model year 2010, the SR400 had fuel injection and a catalyst muffler to comply with tighter emission restrictions" — the genuine turning point that brought this classic single into full modern-emissions compliance while preserving essentially everything that made it beloved in the first place. Bennetts' own review captures the bike's enduring, almost defiantly old-fashioned character even in this later era: "the SR400's air-cooled single engine has remained basically the same since it was first introduced all those years ago and while the latest model does have fuel-injection, it still has a kickstart with no option of any electrical assistance when it comes to getting it going."

Power comes from a 399cc air-cooled SOHC single-cylinder engine with 2 valves, an 87.0mm x 67.2mm bore and stroke, and an 8.5:1 compression ratio, delivering a claimed 23-24 hp at 6,500 rpm and roughly 20 lb-ft of torque at 3,000 rpm through electronically controlled fuel injection replacing the earlier carbureted setup. Wikipedia's own technical account details the genuinely clever dry-sump engineering underpinning this whole platform: "the downtubes of the motorcycle's frame serving as the engine's oil reservoir and cooling system, thereby eliminating the need for an external oil cooler, reducing engine pumping losses, and allowing increased ground clearance as well as reduced overall width" — a real space- and weight-saving trick baked into the fundamental design since 1978, carried forward unchanged into this fuel-injected era. Post-2010 models switched from earlier CDI ignition to transistor-controlled ignition (TCI), and a sealed VRLA battery sits under the seat.

Bennetts' own review details exactly how the kickstart ritual actually works: "the SR comes with a small viewing window on the right hand side of the cylinder head so you can tell when the piston is at the optimum position for starting (there is a decompressor lever to help you get it there with minimal effort) and then a quick kick and as well as the precise fuel-injection, a transistor ignition system gives a lovely big spark and away you go" — genuinely simple in practice despite sounding intimidating on paper. Yamaha expanded the SR400's reach considerably during this era, bringing it to Europe, Australia, and the US for the first time in 2014 after decades as a JDM-exclusive model. Styling stayed consistently faithful throughout this span: a round chromed headlight, a teardrop fuel tank, a one-piece dual seat with passenger grab rail, a chromed exhaust, and wire-spoke wheels with lightweight aluminum rims, riding on a double-cradle steel frame with a telescopic fork (150mm travel) and dual side-mounted shocks (104mm travel). Yamaha finally discontinued the SR400 in the Japanese domestic market in January 2021, closing out a genuine 43-year production run — one of the longest for any single motorcycle nameplate in Japanese manufacturing history — with a Final Edition variant marking the send-off.

This factory service manual covers the procedures, torque specs, and diagrams needed to keep a 2010-2021 SR400 running the way it was built to.