Mice decided to nest in the airbox on my 1999.
What a mess under the cover! Where do they get all that stuff, and why do they carry it up the tires, wheels and frame to build a cozy home in the airbox? (Sorry, I was too miffed to take pictures of the fluff)
I cleaned the airbox with soapy water and a sponge (Careful with those throttle bodies) blew off the filter element and put it back together. Today drove the 44 miles one way to the Honda dealer where I had ordered a replacement filter. (Nice mountain roads, It was not a chore 😉
On the way out and back, when slowed while passing through the several small towns on the route, I noted a new and peculiar soft "clack" when I would pull or release the clutch. BUT, the sound was only noticed when the transmission was IN GEAR. Sitting still, with the bike in neutral, there was no clack! I listened very carefully while moving slowly, pulling and releasing the clutch lever. I determined that the clack noise was coming from that vacuum operated flapper valve in the top cover of the air box. Something I did while cleaning it has allowed the moving parts some extra bit of umph that now it makes an audible sound when opening and closing. I've had the bike since new, and it's never done this before!
The vacuum actuator must be under the control of the ECU, andthe flapp does what it does (opens or closes) under a set of conditions that includes clutch handle position or fluid pressure status. Whatever, it all seems to be functioning. I put a small tab of fabric tape under the flapper to try to cushion the opening clap. It's not like the sound is annoying or anything.
I do know there are multiple threads and comments regarding the utility and performance aspects of this little induction tuning "feature". I could care less,
I try to stay up on how the bike is working, and this "new sound got me for a bit. The new filter is in now, I'll ride again tomorrow.
Just thought to add a little trivial traffic to the forum.
Cheers
mouse urine in an airbox is highly corrosive and can destroy metal.
a
this is what i shook out from a vfr muffler that sat in a shed for too long
[image: gallery_3647_3505_281395.jpg.e7728b98f715a7b3268efd0ecedbc8bf.jpg]
I recall that flapper is open in neutral or when in gear and above 5500rpm. Otherwise it is held closed...unless the clutch switch is activated. I thought I had some sort of high voltage electrical arcing going on based on the sound, but what I heard was the flapper oscillating due to a dirty clutch switch while sitting at the lights in first.
1 hour ago, VTCAL
On the way out and back, when slowed while passing through the several small towns on the route, I noted a new and peculiar soft "clack" when I would pull or release the clutch. BUT, the sound was only noticed when the transmission was IN GEAR. Sitting still, with the bike in neutral, there was no clack! I listened very carefully while moving slowly, pulling and releasing the clutch lever. I determined that the clack noise was coming from that vacuum operated flapper valve in the top cover of the air box. Something I did while cleaning it has allowed the moving parts some extra bit of umph that now it makes an audible sound when opening and closing.
Mine was also doing the clack thing. Sounds like opening a tin can. One day I thought "enough!"
I plugged the vacuum line going to the flapper valve and physically ripped out the plastic valve door thing out of the inlet on the airbox.
And to top it off, I can't stand parts that no longer have a function on the bike, so I twisted off that gold color vacuum actuator
(Honda calls it a diaphragm, air control valve) and riveted a aluminum plate on the open hole on the top of the airbox, just to make it pretty. No more tin can "clack clack!" Seems to idle smoother too.
[image: 20250402_163412-M.jpg]
3 hours ago, mello dude
I can't stand parts that no longer have a function on the bike
I have this curse as well... It's a formidable condition to suffer from.
4 hours ago, mello dude
Mine was also doing the clack thing. Sounds like opening a tin can. One day I thought "enough!"
I plugged the vacuum line going to the flapper valve and physically ripped out the plastic valve door thing out of the inlet on the airbox.
And to top it off, I can't stand parts that no longer have a function on the bike, so I twisted off that gold color vacuum actuator
(Honda calls it a diaphragm, air control valve) and riveted a aluminum plate on the open hole on the top of the airbox, just to make it pretty. No more tin can "clack clack!" Seems to idle smoother too.
[image: 20250402_163412-M.jpg]
Well, there goes the warranty on your 27 year old bike, Dude.
22 hours ago, mello dude
Mine was also doing the clack thing. Sounds like opening a tin can. One day I thought "enough!"
I plugged the vacuum line going to the flapper valve and physically ripped out the plastic valve door thing out of the inlet on the airbox.
And to top it off, I can't stand parts that no longer have a function on the bike, so I twisted off that gold color vacuum actuator
(Honda calls it a diaphragm, air control valve) and riveted a aluminum plate on the open hole on the top of the airbox, just to make it pretty. No more tin can "clack clack!" Seems to idle smoother too.
[image: 20250402_163412-M.jpg]
I would have used gaffer's tape.
Use the plastic flap for the patch and plastic weld it in place.
That's what I did but forgot take pics. Next time ⏲️ ......
iirc someone used some mesh over the openings to keep out 🐁
31 minutes ago, boOZZIE
Use the plastic flap for the patch and plastic weld it in place.
That's what I did but forgot take pics. Next time ⏲️ ......
iirc someone used some mesh over the openings to keep out 🐁
Nice idea....I have plastic sheet stock....tons of rivets too. Probably 8 or 10 ways to do it....
3 hours ago, boOZZIE
Use the plastic flap for the patch and plastic weld it in place.
That's what I did but forgot take pics. Next time ⏲️ ......
iirc someone used some mesh over the openings to keep out 🐁
That fiber mesh tape that dry wallers use might be just the ticket.
I thought about cutting up the screen from the old airfilter element.
So many options, those dang rodents are a bother!
And I store the VFR inside my house all winter!
Ughandi, 8/2/2025 at 6:55 AM
I have this curse as well... It's a formidable condition to suffer from.
Me too, dude! 😁
I think we're many, here inside 😅
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^^^^^^Looks good! :fing02:
Full unleashed power now 🤣
Also removed the lip infront of the flapper opening
1 hour ago, boOZZIE
Full unleashed power now 🤣
Also removed the lip infront of the flapper opening
Great idea.....allows laminar flow into the airbox for even moar power!