Spark Exhaust Bent Tube 30° Ø 48 × 1.0 mm Stainless Steel Universal G9147

Forty-eight millimetres, thirty degrees. Past link-pipe territory and into the section that carries four cylinders at once.

Key Features

• Mandrel-formed 30° bend, AISI 304 stainless steel.
• Ø 48 mm outside, 1.0 mm wall thickness.
• Straight tangents at both ends.
• Matches Spark's 48 mm straight tube, article G9012.
• Spark part number G9147, made in Mantova, Italy.

After the Collector

On a four-cylinder engine everything downstream of the collector carries the whole output, and that section is typically between forty-five and sixty millimetres. Forty-eight sits comfortably in the middle of that band for a middleweight.

On a large twin it works as the entire run from the header junction back to the silencer.

Supporting a Bend

A bend is where a system flexes and where it cracks. The weld at the tangent is a stress concentration, and hanging a heavy silencer off the far side of one without a mount in between is asking for a failure.

Put a mounting point within a hand's width of the bend, and make at least one mount in the system rubber-isolated.

Why a Factory Bend at This Size

Forty-eight millimetres of one millimetre wall is at the edge of what a home setup will form without collapsing. The material is thin, the diameter is large, and the ratio between them is exactly what makes a tube fold rather than bend.

Thirty-two euro against two ruined lengths and an afternoon is not a close call.

Deburring After Trimming

Cutting a bend to length leaves a burr on a curved edge, which is more awkward to reach than a burr on a straight one. A half-round file and a rotary burr in a die grinder both work; a thumbnail check inside the bore is the test.

Clocking Before Tacking

A bend has a plane, and rotating it about the tube axis swings the far end through an arc. On a run with two or three bends in series, that rotation is the entire adjustment available — and it has to be right before the first tack, because afterwards the only correction is a saw.

Ordering

One bend per article. Spark builds 30°, 45° and 90° at this diameter. There is no 180° — only 45 and 50 are bent that far.