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I have order a GPR deeptone for my 2018 YZF-R125. They have emailed saying “GPR have recently updated their range so that these systems include a Catalyser.

We should still be able to order it without, but please just confirm your preference.”

So should I get the exhaust with or without?

My understanding is in the UK they don’t test emissions at an MOT and without the sound will be better and deeper?

A mate (who rides a big boy bike) has said not having a cat could cause issues due to sensors.

What are peoples views on all this?
 

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2008 YZF-R125 (180cc)
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I'd prob get it without. As you say there's no emissions tests for bikes so there's no actual requirement to have it and whilst some restriction in the exhaust flow can be good for torque (mine is def slower without both exhaust baffles), you can add/remove/adjust baffles to suit your bike/tune, you can't do that with a cat.


> A mate (who rides a big boy bike) has said not having a cat could cause issues due to sensors.
hmm maybe. I guess if your exhaust scavenges way better the mix may seem leaner to the o2 sensor and so it may add some extra fuel in but idk. That would likely happen to some extrent with any aftermarket pipe (which actuallyu flows better) which is why the gen1 bikes tend to get slower when you add a big pipe (bc they don't have an o2 sensor and hence don't adjust the fulelling so just run a bit leaner). Also i would have thought if you do experience sensor/fuelling weirdness just adding a baffle mid-pipe would probably fix it.

Is the cat something you can order separately or is removable? or is it a welded-in type thing?

Perhaps ask the manufacturer if there's any known issues with running without a cat?
 
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