Trials Bike Pipes

I do believe that is the reason. A "normal" pipe would not last long in the Trials world ;)

Beta and Montesa use pipes with expanding sections in front of the center box. GasGas, Sherco, and Scorpa use a constant diameter pipe. The expanding head pipe would give better negative waves for scavenging, but it does not make a big difference. All are designed to give a positive wave back from the expansion box (center box). The Beta TR 32 and TR 33 had expansion chambers and they were a little pipey. In European and Eastern US trials conditions, it is important to have very linear power because if you get a little unexpected power when accelerating at the traction limit you will dab at best, not get the traction you need to make an obstacle (5), or crash into the obstacle :scream:.

Doc

Also bear in mind most trials bikes put out about 10 hp. Not very good for bragging at the pub but I am constantly amazed at the ability of these seemingly puny engines. In the bad old days 2 strokes relied on the crankcase as a pump & the exhaust was merely to bleed the gasses out & if you were lucky quieten things a bit. Seems this primitive idea produced smooth power if you use ports that prevent gas short-circuiting too easily.

Indeed my TR3# has a chamber of sorts but my GasGas does not though interestingly the primary muffler was changed between the 2000 & 2001 models supposedly for an improvement in torque.