This blog page is part of the Aprilia RS 250 Workshop Diary.

The RS 250 was sold in Germany with a catalytic converter. Because of the heat caused by the chemical reaction in the catalytic converter, the system is equipped with heat protection plates and stainless steel silencers. The non-catalytic exhaust system has aluminum mufflers covered with a carbon tube. In Germany, most RS drivers call the default non-catalytic system the “italian exhaust”

The installed exhaust system installed was suspected of having already caused engine damage due to parts of the catalytic converter coming loose in the pipes of the horizontal cylinder. I was able to purchase two more exhaust systems, so that I have a total of three exhausts to choose from:

  • Installed German exhaust with catalytic converter with stainless steel rear silencers
  • Newer German exhaust with catalytic converter (used)
  • Unused Italian system without catalytic converter

I wanted to have the Italian system chrome-plated, but because of the many metal sheets, weld seams, folds and ultimately the insulation on the inside, I couldn’t find a galvanic service shop who would do it. Since some preparatory work for the chrome plating had already been carried out (among other things, the welds were re-welded to enable polishing), I only resprayed them at this point.

First I tried to remove the defective catalytic converter from the original exhaust, ultimately with the motivation of not using the new Italian exhaust.

The small catalytic converter in the horizontal pipe has almost completely dissolved, some pieces could still be found in the exhaust. It is interesting that the system for the upright cylinder does not have this small catalytic converter, but instead has a coated sheet metal in the front manifold (not visible on the photos).

The exhaust system was welded back together, I didn’t do so well with the system for the horizontal cylinder, I’m quite satisfied with the upright cylinder pipe. After welding, the system was sanded and painted. I mounted them with two Giannelli silencers for the NSR125 to see how this would look.

For a reuse of the bike on public roads I need a suitable full report because of the long time it was not use, the responsible engineer from would recognize the welds anyway, so I asked him whether this would be okay or not. As an alternative, I still had the other used exhaust with catalytic converter. Interestingly, the motorcycle could also be re-registered without a catalytic converter, as there are also RS 250 registrations without a catalytic converter and a catalytic converter is not mandatory for motorcycles of this model year in Germany. But a driving noise measurement with a correspondingly positive report would be required for the Giannelli silencer to use them on public roads.

The second exhaust system with catalytic converter that I bought (in case re-registration with the removed catalytic converter would be not possible) is now surprisingly different from my existing exhaust system. Instead of the small metal catalytic converter which is coming loose, the newer system has a sheet metal coated with precious metals installed in the front part of the manifold. The difference between the old and the new system can already be seen by looking into the manifold:

I was unable to find the small catalytic converter in the newer exhaust, it was replaced there by the welded sheet metal.

Since I only have legal mufflers for the catalytic converter system and this one does not dissolve itself, I will mount the exhaust pipe with catalytic converter on the RS 250 again, this is better for air quality anyway.

The heat shields and the rear silencers and actually the entire exhaust system have already changed colors due to the heat, the sheets are unfortunately made of brushed stainless steel and polishing brushed material is an extremely time-consuming process, so I painted the whole system in silver, which also suits the rear swingarm color.

The assembly was nothing too special, I couldn’t get the rubber damper pressed into the exhaust, so I just improvised with some leftover parts.

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