Engine pulsing or flutter noise.

[rodb47]

I searched through topics and didn't find anything like this problem. I took my 2017 out yesterday after changing the sprockets and chain (Florida was in the 80s yesterday). I noticed, in 4th gear, while accelerating between 4500 and 5000 rpm the engine would make a fluttering or pulsating noise. It reminded me of Chris Farley saying "Luke, I am your father" into the metal fan in Tommy Boy. Had that type of modulation. It was very prominent and noticeable. I've got almost 17,000 miles on it and have never heard this before. It only happens in 4th gear. Very strange. I'm going to pull off the tank and check the airbox and filter. I synced the throttle bodies about a thousand miles ago. Anyone ever heard this before? Thanks.

[rodb47]

To close out this post, seems that if you put a golf ball size dent in an exhaust pipe it will cause the motor to pulse at the above mentioned rpm. Found a used exhaust for pretty cheap and will swap it out. I looked at the exhausts available for the bike and they are way too expensive for me.

[angrygirafe]

1 hour ago, rodb47 said:

To close out this post, seems that if you put a golf ball size dent in an exhaust pipe it will cause the motor to pulse at the above mentioned rpm. Found a used exhaust for pretty cheap and will swap it out. I looked at the exhausts available for the bike and they are way too expensive for me.

Glad you figured it out. Don’t park that thing on the driving range anymore 😂

[Salish900]

Sure better it being an exhaust issue than an engine issue. That sort of sound on an Aprilia means the engine is toast! 

[peteinpa]

Was it a dent down low on one of the headers? Got a pic?

[NormR]

I'm surprised to hear a dent could cause this pulsating. They way people play (i.e. shortening their mufflers, putting/taking out the db inserts play with a motors back pressure) with their exhaust these days would cause horror scenarios if that was the case....of course if the dent is huge that might be different...

Edited March 2, 2021 by NormR

[rodb47]

1 hour ago, peteinpa said:

Was it a dent down low on one of the headers? Got a pic?

Yes. Lowest header, middle I believe. Don't have a pic right now. I caught the edge of the woodshed floor driving it in. Ramp was too steep. Did a quick check but didn't notice the dent. It's a pretty good dent.

[rodb47]

22 minutes ago, NormR said:

I'm surprised to hear a dent could cause this pulsating. They way people play (i.e. shortening their mufflers, putting/taking out the db inserts play with a motors back pressure) with their exhaust these days would cause horror scenarios if that was the case....of course if the dent is huge that might be different...

Did a throttle body sync check. They were perfect. I figure that a dent in one is causing a pressure differential between the three at that rpm and making the pulsing.

[rodb47]

10 hours ago, Salish900 said:

Sure better it being an exhaust issue than an engine issue. That sort of sound on an Aprilia means the engine is toast! 

The engine pulls great. No other noises or issues.

[rodb47]

Put on the replacement stock exhaust. Flutter is gone at 4500rpm. So I believe I was right about the dent making the noise. Bike runs great. Also added a voltmeter and the SW Motech skid plate. Back to riding again.