Funny little sound when throttle is opened

I have a 6th gen VFR and recently, when riding without earplugs, I noticed a funny little hollow "plunk" or "bloop" sound coming from the top of the engine when the throttle is opened. It happens consistently at about 5% throttle. It sounds like a butterfly valve sound being amplified by the airbox. Is this normal, and is there a remedy to it? Thanks!

PS: no, I haven't messed with my throttle bodies or anything like that.

 

Sounds like the pair valve to me and that noise is normal. There is a way you can block it off and take valve out. Some say it does good and others do not notice much. Search for pair valve removal to find directions.
Someone can correct me if I am wrong though.

 

I tried the PAIR valve block. But I didn't care for it, so I reverted it to stock.

 

You can re-do the valve removal for the purpose of verifying if this noise is the PAIR valve. If yes you can replace it.

Before you do that, maybe you could lift the tank and observe the butterflies and see if one is sticking? I am unsure how the starter valves close, but if they stick do they slam shut? Again you could observe the starter valve movement.

In terms of valves there is also the bypass valve on the air cleaner.

The old car trick is to put a medical tube to the ear and move it around under the hood. It filters out everything you are not pointing at, and gets very loud as you approach the offending part. You could do this while someone pulls the throttle.

 

Underoath, at what revs is this happening? If it is right around 5500rpm then the sound is probably the flapper valve being opened.

The VFR has a couple of solenoids that are driven by the ECU, one for the flapper as above, the other for the PAIR system. You could try unplugging the electrical connections for these one a a time to identify if that is the cause.

You can test the flapper while stationary but it only operates in gear; you can trick the ECU by pulling off the neutral switch wire on the side of the clutch cover, then you can safely rev the bike in neutral but the ECU thinks you're in gear and drives the solenoid.

 

It could be a drunk leprechaun in the air box....................

 

Yup... It's the flapper valve. They all make a little noise. It's not a problem.

 

I agree that the flapper valve sounds like the likely culprit. I'm not going to bother digging around under the tank unless the sound changes. Thanks guys!

 

I have the same sound coming from my 06 VFR at 1,300rpm.
The sound is not there above or below 1,300.

 

The only way to test for that is to tip a little Guinness into the fuel tank. I don't remember if that makes leprechauns louder or quieter.

 

I have the same sound as well .I take that as pair valve.

 

Thanks for the advice mate but I'd rather tip the Guiness in my mouth.

 

So you did the pair valve modification and that fixed the problem?

 

Hey Gino, not sure who you are asking here. I don't think the PAIR elimination would make any difference to noises around 1300 rpm. I mean, that is at or below idle, and I would never notice that. For me, the PAIR removal just trashed a whole lot of useless plumbing. For you 6th gen owners I understand it can improve low rpm running by removing an effect on the O2 sensors.

The VFR (well my 5th gen) does make some noises sometimes as a result of the clutch switch and the flapper solenoid when idling in gear at traffic lights. If the clutch switch is a little dirty it can make intermittent contact and that causes the flapper solenoid to make a buzzing sound; this sounds a bit like electrical arcing. Cleaning or replacing the switch fixes that.

 

The sound only happens in gear (clutch in or out) at 1500 rpm. I can bounce the revs back and forth through that range and make the sound each time the tach needle crosses it. Does that still sound like it's the flapper valve?

 

The funny little sound that I experience when opening my throttle is me yelling with excitement

 

I get that sound too.

 

For those that state the flapper valve is making the noise, I have to strongly disagree. I too thought it was that, so I unplugged and blocked the vacuum line to it. No effect. I then removed my PAIR valve and the bloop was gone. I am currently running with my flapper hooked up and the PAIR gone and I do not have the sound. It was always there upon opening the throttle at low RPMS. Disconnect the flapper and you will still have it, at least with a 6th Gen.

 

Me too. It's something that happens automatically and increases in volume in direct proportion to the amount of throttle given.

 

Lint you're correct that the flapper won't cause this as it only activates at 5500rpm and is closed below that point.


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