intermittent (crunching)engine noises

I have a 99 vfr and recently after giving it a fistful one day I started hearing some horrible crunching noises coming from the front of the engine somewhere.  a weird noise to describe , if u get a plastic beaker half fill it with small stones then give it a sudden jerk one time, causing the stones to shift suddey from one side of cup to the other! Then thats close!  Is this the cct probs people have identified, wot can I do if so? Bike performs as normal apart frm intermittent crunching sounds, thanks

yours is gear drive cams no chain but cant help u with the noise tho sorry

Time to pull the rocker covers off and take a look.  Maybe shoot some slow panning video for us and post to YouTube so we can take a look.

Does this noise happen when the bike is moving, or sitting still, or both?

Check your airbox flapper valve. Disconnect the vacuum line and plug it temporarily.

Ride the bike and see if the noise goes away.

[image: View Post]Veefer800Canuck, on 06 June 2012 - 06:59 AM, said:

Check your airbox flapper valve. Disconnect the vacuum line and plug it temporarily.
Ride the bike and see if the noise goes away.

That came up in this thread too - http://www.vfrdiscus...ning-great-but/

Please know, I appreciate your reply and thought, but you are speaking WAY OVER MY HEAD, I'm not a mechanic, can you explain this better?

Tip your fuel tank up at the front and prop it up.

The top of the airbox will look like this:

[image: index.php?app=gallery&module=images&section=img_ctrl&img=598] 2006 HONDA VFR 800 V 800491 Airbox 12 004 Album: Misc pics Uploaded 06 Jun 2012 - 07:10



The round gold thing at the top is your airbox flapper actuator. The hose coming off of it is the vacuum hose. Disconnect the hose from the gold thing, and plug the hose securely with something suitable.

Button the tank back down and take the bike for a ride. Did your noise go away? If so, it's your flapper valve that is rattling as it opens and closes. Sometimes it opens and closes rapidly and flutters a bit, making a noise.

I have no issues with flapper valve noises, hehehe.

Flapper go bye bye.

[image: Posted Image]

Dude, that's awesome, thanks

So what does the flapper valve do and how can you live without it so easy?

For sure now I know what to do I'll pinch that line and see what happens

It increases air flow velocity by creating restriction at lower engine rpms.

-Jake

Thanks for your help all, the noise happens at idle, never heard it under acceleration, I will remove the pipe and see if it makes a difference, any other suggestions??? Cheers

Thanks for your help all, the noise happens at idle, never heard it under acceleration, I will remove the pipe and see if it makes a difference, any other suggestions??? Cheers

Well I ordered the clutch swith too, I figured for a few bucks why not, pluss I needed a few specific little screws and some biulbs and I figured I would check out Mason City

[image: View Post]Jakobi, on 06 June 2012 - 11:05 AM, said:

It increases air flow velocity by creating restriction at lower engine rpms.
-Jake

I'm going to be changing out the OEM paper air filter with a K&N, so I'll play with that vacume line when I pull the tank out to do the filter
I appreciate the help

Every now and again I can hear mine flap open and closed at idle if I'm playing with the clutch and throttle a little. Seems to happen more when its cold. the sound is almost exactly what you describe on my bike.

check the fan blades

[image: View Post]TripleH, on 06 June 2012 - 09:49 AM, said:

Dude, that's awesome, thanks

So what does the flapper valve do and how can you live without it so easy?

For sure now I know what to do I'll pinch that line and see what happens

Don't pinch the line, completely disconnect then plug it. Then test for the noise while riding.

Or, simply leave it alone and let it do its job.  Though theoretically possible, it's not likely you know more than the engineer who designed the airbox for the motor.  Mods aren't always good.  As another posted, the flap's purpose is to maintain proper airflow velocity at lower engine speeds, while allowing extra flow at higher engine speeds.  Win/win - good low speed driveability and good power up top.  Almost like an engineer designed it.

K&N filters allow dirt into your engine, which is how they can flow more than the stock filter.  You could look it up.  Stay with the paper filter.  There is no free lunch.

I wouldn't buy a used bike with a modified airbox or a K&N.  Based on long experience buying bikes, I'd be worried the bike had other such mods, and it's not worth it to me to fix another's mods.

You mentioned a CCT in your first statement.  your 2000 VFR doesnt have a CCT (thank god!)  Therefore you won't hear  it rattling and screaming to come out (like on CBR's and newer VFR's)

[image: View Post]Misspent Youth, on 07 June 2012 - 09:35 AM, said:

Or, simply leave it alone and let it do its job.  Though theoretically possible, it's not likely you know more than the engineer who designed the airbox for the motor.  Mods aren't always good.  As another posted, the flap's purpose is to maintain proper airflow velocity at lower engine speeds, while allowing extra flow at higher engine speeds.  Win/win - good low speed driveability and good power up top.  Almost like an engineer designed it.

K&N filters allow dirt into your engine, which is how they can flow more than the stock filter.  You could look it up.  Stay with the paper filter.  There is no free lunch.

I wouldn't buy a used bike with a modified airbox or a K&N.  Based on long experience buying bikes, I'd be worried the bike had other such mods, and it's not worth it to me to fix another's mods.

I'm not planning to remove the vacume line forever, I simply want to stop it from working long enough to figure out where the noise is coming from. In my book there is no negative to understanding exactly what is causing this noise, that partially sounds like the entire electrical system on the bike is aboiut to fry...

Opinions cary on foam filters, have had one on a Honda CRX-Si, over 9,000 track miles, with 110,000 stereet miles, and the compression leak down test is still even and extraordinary, filter has been kept clean, and, key here, properly oiled.

[image: View Post]DFOTECH, on 07 June 2012 - 09:35 AM, said:

You mentioned a CCT in your first statement.  your 2000 VFR doesnt have a CCT (thank god!)  Therefore you won't hear  it rattling and screaming to come out (like on CBR's and newer VFR's)

Who you?

[image: View Post]TripleH, on 07 June 2012 - 09:43 AM, said:

I'm not planning to remove the vacume line forever, I simply want to stop it from working long enough to figure out where the noise is coming from. In my book there is no negative to understanding exactly what is causing this noise, that partially sounds like the entire electrical system on the bike is aboiut to fry...

Opinions cary on foam filters, have had one on a Honda CRX-Si, over 9,000 track miles, with 110,000 stereet miles, and the compression leak down test is still even and extraordinary, filter has been kept clean, and, key here, properly oiled.

Roger that.  You may or may not find this to be of interest re: K&N filter dirt capture/passing effectiveness:  http://www.nicoclub....oem-filter.html