Engine Stumble & Airbox "backfire"
 

I own a 2009 Suzuki Gladius with only about 1500 miles/2400 km on it. When trying to hold a steady throttle at anywhere between around ~2500 to ~3800 RPM the engine begins to struggle sometimes stumble and the bike loses speed. Even with a steady throttle. Anything above 3800 feels fine.

Sometimes during the stumble AND sometimes when I blip the throttle, I get a loud "FWUMP" noise and the engine cuts out for half second. I can feel the that "fwump" between my knees near/in the airbox.

Any ideas? The engine stumble/pop happened midway through a turn at an intersection last night and almost caused a high-side. I'm a bit hesitant to ride at this point until I figure out whats up.

Some folks are saying it may be the throttle position sensor. Mine kicks in at around 2000 RPM right now so I'm not sure if lowering that would help much since it appears to be calibrated correctly.

Any input would be greatly appreciated!

Re: Engine Stumble & Airbox "backfire"
 

It is worth setting TPS correctly but that is not the usual way it manifests itself. You may have a problem with one of other sensors on there, perhaps air pressure or temperature one in airbox.

Re: Engine Stumble & Airbox "backfire"
 

Is it still under warranty?

Re: Engine Stumble & Airbox "backfire"
 

Unfortunately it's not under warranty as of late November. I did take it in this past July and the dealership gave me flack about the slip-on & voiding the warranty, supposedly took it on a 20 mile ride but couldn't reproduce the issue then went back to blaming the slip-on causing a lack of back pressure. Second dealership I took it wouldn't even honor the warranty due to the slip-on. Shady places out here.

I've been traveling a lot for work so haven't had much time to ride since September but it seems to have gotten significantly worse.

Re: Engine Stumble & Airbox "backfire"
 

Ah this is interesting I had the EXACT problem on my 04 pointy, I would get the 'thwup' sound and jerk as the engine appeared 'kick in' again, usually half way through a bend or when I'd roll off the throttle and then back on again.

I also told my garage about it, they took it for a spin and surprise surprise they couldnt replicate it either! Needless to say I never found a solution to it. I sold the bike and have since bought an 07 pointy and its done it once on this bike which annoyed the funk out of me, but luckily not happened again.

If you find the cause or a solution do share as i'd love to know wtf it is!

You're not alone brother! :(

Re: Engine Stumble & Airbox "backfire"
 

In the 5 years I've had my SV, I've only ever had an 'Airbox backfire' feeling twice. Once was about 30 seconds after starting the engine with it on tick-over, and another time was rid-ride out just going along at around 30/40mph.
I just put it down to a weird mis-fire, but I'd be intrigued to know if there is a known cause.

Re: Engine Stumble & Airbox "backfire"
 

Check your plugs, HT caps n' leads, connections to the coils!!!

Re: Engine Stumble & Airbox "backfire"
 

When your holding the throttle steady at 2500rpm what gear are you in?. Id look at throttle body balance and TPS - the balance can only be done correctly with the SDS software due to the idle speed control valve. Id get that checked.

Id also consider getting the fueling checked on a dyno as adding a slip on can affect this dependant on the bike.

Those dealers shouldnt have turned you away from inspection to determine the cause of the issue because it had a can fitted. If the can was causing the running problem then ok it wouldnt be under warranty.

It could also happen if your in a very high gear, say 5th at those revs and your on very small throttle openings, try using a lower gear.