Spark Exhaust Bent Tube 45° Ø 32 × 1.0 mm Stainless Steel Universal G9127

Thirty-two millimetres through forty-five degrees. The everyday angle in the first of Spark's thin-wall sizes.

Key Features

• Mandrel-formed 45° bend, AISI 304 stainless steel.
• Ø 32 mm outside, 1.0 mm wall thickness.
• Straight tangents at both ends.
• Matches Spark's 32 mm straight tube, article G9006.
• Spark part number G9127, made in Mantova, Italy.

The S-Bend

Two 45° bends facing opposite ways, with a straight between them, produce an S. The run leaves in one direction, steps across, and carries on parallel to where it started.

On a small machine that is how an exhaust gets from a header on the centreline out to a silencer mounted at the side of the frame. It is the most common shape in motorcycle exhaust routing and it is built from this article twice.

Where 32 mm Belongs

Header and link diameters on machines between 250 and 400 cc. Small enough to keep gas speed up on a modest engine, large enough not to choke it at the top — and the size several of Spark's db killers use as their internal bore.

Clocking Two Bends

An S only works if both bends lie in the same plane. Rotate one of them a few degrees about the tube axis and the run no longer comes back parallel — it corkscrews, and the error compounds over the length of the system.

Assemble with tape on a flat surface first. A bench top is a better reference than the motorcycle for this particular check.

Springback

Stainless springs back four to eight degrees when a bender releases it, so a hand-made forty-five has to be pulled past fifty. A production bend has that compensation designed into the tooling and arrives at forty-five measured.

Weld Preparation

One millimetre wall does not want a chamfer — there is not enough metal for one. Square cut, tight gap, clean metal, wiped with acetone rather than brake cleaner, and a stainless brush kept for stainless only.

Heat Tint as a Diagnosis

Stainless colours where it has been hot, and the colour tells you how hot. A straw or light-gold band beside the bead is normal. A grey, powdery band is not: the weld overheated and chromium has been drawn out of the surface. That band will rust, and pickling paste is the only thing that fixes it.

Ordering

One bend per article. Spark builds 30°, 45° and 90° at thirty-two millimetres, and a 500 mm straight length.