How To: YZF R125 Desrestrict Exhaust

I managed to get hold of an 08 exhaust from ebay for £40 so i thought id mess about with that and keep mine stock if i need to swap it back. Performance system range from about £300 upwards so for 40 quid, it was worth a shot. I had a friend cut and reweld the stock exhaust to see what he could do with it.

Heres some pictures of the standard system.

Above is a picture of what looks like a restrictor, this bulged section contained a honeycomb like cross section.

To the right, you can just see the small tube coming off the exhaust, this is the fresh air bypass tube which comes from the valve on the bike. Aftermarket exhaust wont have this tube on it.

Heres the exhaust back from my mate.

The first thing my mate done was to chop out the restrictor section and reweld and new section of pipe.

Next he removed the small tube and welded it closed.

Finally, he cut out the cat section and drilled out the centre so it was hollow. He then rewelded that back on.

There was little we could do with the rear can, as it would be baffled and the engine would need some form of back pressure.

Results wise, it seems to ride just as good, however i have noticed that the top end is better, i can maintain motorway speed easier, and the bike pulls better up high rpm.

I have however fitted both my air filter mod and now the exhaust in conjuction with a power commander 3 and its now running a more aggressive fuel map.