250-500cc Modifying Emission Version Expansion Chamber as a Spare

When I bought my 2011 WR300 it came with 2 Expansion Chambers.

The non emission control expansion chamber has no distinguishing features and looks normal.

The Emission Control Expansion Chamber has what looks like a catalytic converter where it mounts to the barrel and has clearly been extended (with a weld) by probably 30mm.
- It is fatter
- The silencer fitting end is different and does not have a stopper welded on it.
- Has a small diameter Tube coming up from the inside pointing towards the handle bars (bleed tube for charcoal canister???)
- Has 3 spring locating rings whereas non emission only has 2
- Is Physically larger and heavier
Has anyone removed the Catalytic Converter honeycomb, cut and welded the small bleed pipe, modified the silencer end and used it as a spare expansion chamber.

By the looks of it, re-jetting may be needed too as the mid section is fatter and the outlet curve is longer.

Please discuss...









Stu

Howdy, I recently cut one of these up. There is another larger diffuser tacked inside the main belly of the pipe. Thats the extra weight. Also a restrictor
washer welded to the inside end of the stinger, 10-12 mm dia.
Cheers

You learn something new every day. Had no idea. I'm sure you could modify it to work as normal.

I did it on mine, its a WR250 -07 but looks very similar.
It had two catalytic converters, one on each side of the air inlet (small tube) and there was a washer welded at the end of last cone. I did not do the work myself, a friend who is a good TIG welder did it for me.
I cant really say if there was any difference in performance, I could not test the pipes back to back because my racing pipe was thrashed.. but I did not change jetting

Thanks for info.

Probably wont waste my time with it.

Stu

gday Stu,

I have had it done and I have just fitted after it was getting a bit tricky to bend my original into a shape that fit. Cost me $50 and I got another pipe repaired at the same time for the same price.

He is just out of Sydney so probably a bit far for you but your should be able to find someone down there that can do it for you. Let me know if you want his number.

Stu

throw it in recycling bin Stu. that piece of junk cost me a ride a while back. got cat conv out with much bashing & cursing, had hole welded up, managed to get it to mount up(nightmare & more bashing/cursing again), loaded bike up, drove to area was gonna ride, started it up & it ran like a piece of poo! didn't realise about the stinger end washer restrictor. went home, took pipe off bike, bashed it senseless with a hammer, threw in bin & drank beer wasted hours on that fricken pipe! not sure what youd use it for as it makes bike downright dangerous to ride, has all the acceleration & power of a lawnmower

remove all of these

did this back in the day when the dealer gave me a couple for nix when waiting for a gnarly. Seemed like such a waste tossing them in the steel bin on delivery. FYI the washer in the stinger made the biggest impact on performance, minor difference from the honeycomb staying in there.

My actual pipe was modified by the previous owner and I plan to do the same with my other new restricted pipe, they are no strong pipes but having one it worth the welding I think.


Regards.