Engine Backfire after decelaeration.

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Hi all,

I'm interested in one second hand MV and the owner said that "The engine will back fire when you come off the gas after hard deceleration. This is quite common."

Is it supposed to do that.

Curious buyer.

-- Nils Haak (nhaak@algonet.se), March 07, 2003


The Eprom (fuel and ignition mapping) for the RG3 as well as the standard MV Arrow exhaust for certain model years have been revised a number of times according to my dealer that is Authorized MV Agusta in Italy. Look into it.I had a slight mapping problem and it was repaired by changing the Eprom w/ RG3 EVO 02... I had seen with my own eyes the 2 different part numbers on the chip itself. I am sure that this wont be admitted by most dealers.

-- giorgio (giorgio@ureach.com), March 07, 2003.

Ok. Thanks for the info. Will look into it if I buy this bike.

-- Nils Haak (nhaak@algonet.se), March 07, 2003.

I've had mine 2 years (had the RG3 exhaust installed when I bought it) and it has done that from day 1. I've heard it just needs a bit more fine tuning on the chip (a CO screw or something), but since mine runs very well I haven't bothered with it.

I wouldn't worry about it any.

-- Brad Cowell (bcowell@sbcglobal.net), March 07, 2003.

I've have the '00 F4S with stock pipes. Mine had to be adjusted twice backfiring after quick deceleration. My mechanic at Motofixx in CT just adjusted the CO mixture. I believe he said it was known to happen to these bikes. A screw which controls the mix may loosen at times. I have over 12,000 miles and this occured only twice. It's a quick fix. If it's not happening constently every time you roll off the throttle then I wouldn't worry about it. But it you're riding hard all the time and at every roll off it happens then you can look into the CO mixture. You may be running too lean on top.

Just my 2 cents, Tony Perez

-- Tony Perez (tonymvf4@aol.com), March 08, 2003.

Mine does it every time a ride it. If i blast for a couple of miles with the revs above 8000 rpm to the rev limiter, then slow down to about 5 or 6000 rpm it always lets out an almighty backfire (or two). F**king loud in tunnels!I,ve now learnt when it occurs now, so i can make it happen when i want to. All good fun, making the old ladies jump out of their skin! just kidding. There seem to be no other running problems, little fluffy between 3- 5000 on a constant trottle through towns and stuff, but doesn't worry me cos is fine when i'm riding the bike how its meant to be riden. (2001MY on standard pipes and i love it). Happy and safe riding to you all, Paul

-- paul h (paulh996@nildram.co.uk), March 08, 2003.

Yes, mine does it too, every time you ride hard then roll off the throttle. Sounds too good to make me want to get rid of it, and the bike runs ok at all revs, so no need as far as I am concerned. Let it backfire and enjoy the sound !

-- David Stephens (david_stephens@storagetek.com), March 10, 2003.

Nils, upgraded my 00 F4s to performance Blueflame pipes and got my hands on a SPR chip. The thing back fires a treat on major decelaration. This is especially the case on Higher Octane europe fuel. I have my EPROM checked and cleared regularly by the dealer (Powerhouse, Kent) on a rolling road and there doesn't appear to be any problem - just enjoy it!

-- Steve (Steve.hunter@btopenworld.com), March 16, 2003.

In almost any scenario involving a backfire, it is caused by residual unburnt fuel/air mixture making way into the exh pipes.

If the bike is set too lean at closed throttle, then there is an engine misfire. The mixture, although somewhat lean, is left to exit the pipe unburnt from the C Chamber. One good burn cycle in the chamber will produce sufficient heat to ignite the mixture remaining in the pipe--BAM! This is why a lean engine will backfire mort than one set up correctly.

Subsequently, if a mixture is also too rich, the residuals will find their way into the pipe and any air leaks (Italian slip-on pipes HAVE air leaks) will introduce more oxygen into the pipes and that's enough to have another round of burning--BAM!!

Hope this clarifies why anyway.

Jim Cooper - Technician/MotoFixx MV Agusta

-- Jim Cooper (coop747@optonline.net), March 16, 2003.

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