Spark Exhaust Bent Tube 45° Ø 42 × 1.0 mm Stainless Steel Universal G9121

Forty-two millimetres at forty-five degrees. The working angle in the size that exists because manufacturers do not build to round numbers.

Key Features

• Mandrel-formed 45° bend, AISI 304 stainless steel.
• Ø 42 mm outside, 1.0 mm wall thickness.
• Forty millimetre bore — 40 mm tube slides straight in.
• Matches Spark's 42 mm straight tube, article G9008.
• Spark part number G9121, made in Mantova, Italy.

Adapting to What Is Already There

A great many custom exhausts start at an existing header rather than at a blank sheet, and that header is whatever the manufacturer chose. Forty-two turns up often enough that Spark keeps the size, and matching it saves both a transition piece and the flow disturbance a transition causes.

Measure across the outside with a vernier. A workshop manual figure is usually a nominal internal dimension and will send you to the wrong article.

A Corner With a Socket in It

Forty-two outside on a one millimetre wall gives a forty millimetre bore, so a 40 mm pipe pushes straight into the end of this bend. The corner and the coupling become one part, with no sleeve to make and no butt weld to align.

On a project built in forty millimetre tube, a couple of these turn a welded system into a serviceable one.

Measuring an Angle Accurately

A digital angle gauge on the two straight tangents is worth more than eye judgement, particularly when two bends are being combined. Half a degree of error at the first joint becomes a centimetre of misalignment at the silencer.

Chamfering the Male End

If this bend is going into a larger sleeve, break the outer edge of the cut with a file. A square edge catches on the way in, raises a burr inside the sleeve, and that burr is what stops the joint coming apart again for service.

Ovality Where the Curve Ends

Any bend is least round at the tangent point. On a mandrel-formed piece the deviation is small, but a tight slip fit will find it. Measure across two axes before assuming a pipe will slide in, and round the end on a mandrel if it needs it.

Ordering

One bend per article. Spark builds 30°, 45° and 90° at forty-two millimetres.