I have an MV Agusta Brutale 675 with a GPR Carbonox slip on installed. The air filter is stock and no work has been done on the ECU. My problem is: at this state it's running rich as one can smell un burnt gasoline in the exhasut fumes. It's also got poor mileage as well. I'm thinking about installing an aftermarket air filter i.e DNA, BMC, etc which would hopefully remedy this, however plan on doing so without installing an aftermarket feul controller (i.e Power Commander, Bazzazz). Will this fix my problem or worsen it?

  • What year is your bike? Welcome to this site. Cheers! Commented May 13, 2016 at 15:54
  • 2
    Why do you think the aftermarket exhaust is the issue of your bike running rich? It seems to me it wouldn't have any affect on this. Putting an aftermarket air cleaner on it may help the situation, but from my point of view, it's doubtful. Commented May 13, 2016 at 16:58
  • I would love to see the results of an A-B-A test. Test with this exhaust, run 50 miles, measure fuel economy (A test) go back to previous exhaust, do same 50 mile run, measure fuel economy (B test) than go back to this exhaust. same test a third time. I really don't know the logic for throttle control --> air fuel mix. Electronic control (hot wire anemometer, vacuum signal, pressure plate, rotary encoder ) or perhaps carbureted? I would expect a change in airflow from the slip on. Without know the specific logic of the controller who knows what it will do.
    – zipzit
    Commented May 13, 2016 at 21:53
  • @DucatiKiller, shes a 2014 model
    – glenrules7
    Commented May 14, 2016 at 8:23

1 Answer 1


If anything, your bike should be running lean


You put an aftermarket non-restrictive exhaust on your MV, that increases the flow of gasses which requires more fuel to compensate for the additional flow. So, the idea that your bike is running rich doesn't really resonate. It certainly can be and if it is it could be indicative of another issue within your fuel delivery system.

Air Filter

A free flow air filter will give you a higher flow rate through your intake than an OEM filter typically. This will add the ability for your engine to consume more gasses, in this case, air. Which in theory would reduce richness, but wait....there's more.

You have an ECU, it monitors your intake and exhaust. It should be providing the correct richness without a Power Commander. Why would it be rich? It shouldn't be rich. It should be leaner.


You have something else wrong with your system. You should clean all your sensors. MAF, oxygen....all of them. Once they have been cleaned, go for a ride and get everything good and hot and then see if it still smells rich.

The K&N and Power Commander are great low cost HP upgrades but I believe you need to understand what is happening with your bike in it's current state, fix it, then add those pieces in. Your bike should not be running rich or lean, it should have perfect AFR and there is a reason it doesn't. You just need to find it. Also, clean your plugs and check your wires and ensure you don't have a misfire.

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