Category Archives: Expansion Chambers

Highwayman Pipe Tuning: exemplified for the Yamaha TD3 250cc twin

Achieving a specific tuning goal with pipe design.  The goal was to achieve equal or greater power while moving  the red-line from ~13,000 RPM to a max of 11,000 RPM. The pipes on the bike kept wanting to pull way past 11000 RPM, and the owner wanted to keep the power below that to preserve crankshaft life, while not loosing race winning power!

Design and construction of The Highwayman F37 road racing chassis, Part II

This is Part II of the F37 story that covers the design and fabrication of the thin wall chromoly road racing chassis. Construction of the engine and some racing footage aboard the finished bike can be found here in Part I.

The Highwayman F37 a custom, purpose-built vintage road racer, Part I

This story highlights the creation of a road race engine from the fusion of two different enduro motors, as well as the design and fabrication of a custom racing chassis to house the “franken-motor.”

Stainless Denco replicas for the Kawasaki H1

I needed chambers for a Kawasaki triple that I was restoring and decided to make my own after being disappointed with what was available for these bikes. The goal was to make exact copies of vintage Denco chambers to ensure good performance and stick with the period look.

Complex stainless GP style pipes with 54 cones total!

This was a project for a friend who needed a custom set of expansion chambers for his Yamaha RZ350. This special RZ350 had been modified with an Aprilia RS250 swingarm. He liked the way Spec II RZ pipes performed  so we used them as a model, but also made some innovations. I call this design “RZ350 Spec III.”

Also included in this post are some pipes for a RZ350 motor in an RS250 chassis…

Broad band power for the Kawasaki A7 350 rotary valve twin

The Kawasaki A7 Avenger 350 cc rotary valve 2-stroke twin is a fun little bike.

I was surprised to find how quick these things are, and do hear they were very progressive for their time!

Expansion chambers for an airplane!?

When I got a call to make a set of expansion chambers for “The world’s smallest manned twin engine airplane” I just could not resist!

The Colomban Cri-cri (or Cricket) was designed in the early 1970’s by Michel Colomban. Since then many renditions have been built. Most Cri-cri aircraft are powered by two single-cylinder 2-stroke engines making 9-15 HP each. However this Cri-cri is special in that it has two twin-cylinder 2-strokes as the power plants!