KTM exhaust pipes

What's the Difference?

by Alan Buehner

Trying to identify a KTM exhaust pipe can be confusing and frustrating especially if you have no idea what year or size of bike that it came off of. Even if you have several KTM pipes together with no identification, at least you can compare them side to side to try and find some differences.

The 175 and 250 pipes look almost identical. The difference between the two is how the pipes were constructed (welded together).

The 250 is easy to spot in that it has a continuous seam from the header to the back of the cone. It is basically two stamped out halves with a joint seam welded together and the back part of the cone then welded to the front part. (see photo A)

The 175 pipes have three welded together sections. There are the two front stamped out halves welded together, joined to the center cone, which is then welded to the back cone section. (see photo A)

Photo A - showing a KTM 250 pipe on top and a KTM 175 pipe on the bottom. The 250 has only 2 sections welded together to form the expansion chamber. The 175 has 3 sections welded together to form the expansion chamber.

What makes the KTM 400 pipe stand out from the 250 is the curvature of the pipe from the header. The 250 is “J” shaped with a gradual 180 degree curve from the manifold to the expansion chamber. The 400 pipe his two 90 degree sections welded together and then welded to the expansion chamber. (see photo B)

Photo B – A KTM 400 pipe is on the left a KTM 250 pipe is on the right.

One other thing to help identify a KTM 125 exhaust pipe from a 175 or 250 pipe is the diameter of the opening for the exhaust manifold.

The KTM 125s use a smaller diameter exhaust manifold. Thus, the diameter of the pipe end is also smaller than the 175 or 250. (see photo C and D)

The KTM 175, 250 and 400 all use the same size exhaust manifolds. Their pipe ends are also the same diameter which make them look alike.

The KTM engines from 1973 to 1975 use a straight manifold. The 1976+ engines use an angled down manifold and the neck to the exhaust pipes are angled up to fit these manifolds.

Photo C – showing from left to right – a KTM 250 pipe, a KTM 175 pipe, and a KTM 125 pipe. Note the angle of the 125 pipe on right. It is designed to fit the angled down manifold.
Photo D – showing the different types of manifolds used on the Penton/ KTM bikes.
Top left – manifold used on the Sachs 125 engines
Top right –angled manifold used on KTM 125 engine
Bottom left – straight manifold used on KTM 175, 250, and 400 engines prior to 1976.
Bottom right – angled manifold used on KTM 175, 250, and 400 engines after 1975.