I never fully understood 2-strokes, they're a completely different kettle of fish!

2-stroke expansion chambers are a dark art, and no mistake. MZ's Walter Kaaden applied the knowledge he'd gained working on the pulse-jet motors that powered V1 rockets to develop them for MZ's racing programme in the 1950s. Arranging 'cone' shapes in the exhaust pipe exploits the pressure wave that travels in the pipe, so you can use the wave to a) suck fresh mixture into the cylinder and then b) keep it there while it goes bang. But only in a specific rpm range ....

Walter Kaaden, didn't he take all of his and MZ's secrets and hand them to Suzuki?

No, it was the MZ team's star rider, Ernst Degner, who was approached by Suzuki in 1961, and as a result defected from East Germany for £10,000 plus a job as Suzuki works rider and developer, taking with him various MZ engine parts (cylinder, piston, disc valves etc).

Suzuki were a laughing stock in GP racing at the time. Degner was an excellent racer and also a skilled development rider under Kaaden's tutelage.

The deal was that Suzuki would enable Degner's (and his family's) defection if he would guarantee to develop a 125cc race engine for Suzuki that produced 25bhp ready for the 1962 season. So he stole Kaaden's know-how and took it with him to Suzuki.

I can highly recommend 'Stealing Speed' by Mat Oxley (published by Haynes), which covers the entire story, from Kaaden's wartime experiences to MZ's retirement from racing and Degner's death, taking in the lethal world of 60s GP motorcycle racing. It's a fantastic, absorbing read.

Thanks everyone. I am right then in thinking a dual exhaust is basically a waste of resources without any advantages ? I had just wondered if it might increase maintenance costs and possibly be a source of problems.

However, probably nothing either way.

Mazda CX-5 has two tail pipes coming from one back box, no idea if they increase performance, but the multiple manifold out pipes i would expect do.

Theres only one exhaust pipe going to the rear.