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Clutch Noise


mkrouse

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I have a 1999 VFR800FI with over 69,000 miles. Runs well.

I noticed a sound today while riding in my neighborhood, warming the oil for change. No helmet. No earplugs. Crawling speed.

The sound is like a crackling electrical connection. Occurs only with power switch on, bike in gear, clutch lever released just prior to engagement. Engine does not have to be running, ignition must be on.

 

So, what's about to explode?

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I could be wrong but... one of the things on the 5th Gen that changes as the clutch is released is the status of the variable intake flapper valve's position (on the intake airbox).  Wondering if the weird sound you're hearing might be a result of something related to the bike's vacuum lines (and related to the flapper valve).

 

The bike's PGM-FI ECU makes the "call" on when the flapper valve opens or closes.  I think it uses at least these three parameters: clutch position, engine RPM and (possibly) gear selection (specifically the neutral position signal).  And the whole thing is actuated by an electrical signal supplied by the ECU to a solenoid valve that's located on the lower right-hand side of the bike's airbox.

 

I think that the flapper valve does this: at idle or low engine speed with clutch "in" and gear selector not in neutral the flapper is open,

 

Then, as clutch is released (with gear selector not in neutral) and engine RPM speed below the "flapper open" threshold value the ECU commands the flapper to close,

 

Then, in any gear, as you run the engine up through the RPM range the flapper is closed until you cross the "flapper open" threshold RPM value the ECU commands the flapper to open.

 

Maybe that's more info than needed here but, it might be worth focusing your "listening" on the vacuum controls and plumbing elements around the bike's airbox to determine whether that's the source of the odd sounds, concentrating on the controlling solenoid valve.

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Well, that does sound a lot like a solenoid valve that's not getting the full electrical voltage it needs to open (and stay open).  The sound of a malfunctioning solenoid is usually a "rattling" noise, which is what I believe I heard in that sound file you just posted.  The solenoid is a small electromagnet located around an iron core (which is held in a "closed" position with a return spring).  With enough electricity supplied the electromagnet is able to lift the iron core upwards against the return force of the "closed" position spring.  When the electrical signal is either weak or intermittent you'll get exactly this sort of bouncing/rattling noise.

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So you're saying that (in the sound file you included) the bike is making this sound in response to you moving the clutch in-and-out?  And that's the only item that's changing during that sound file?

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Greg you are exactly right in the cause of this sound. I think you'll find the clutch switch is a bit dirty and making intermittent contact so the solenoid is buzzing. Some contact cleaner in the switch should help, or adjust the clutch lever position a bit. 

 

A new clutch switch is also a cheap thing to replace. 

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1 hour ago, GreginDenver said:

So you're saying that (in the sound file you included) the bike is making this sound in response to you moving the clutch in-and-out?  And that's the only item that's changing during that sound file?

Yes, exactly. As the clutch is eased out slowly. Stops when all the way out or in. I think I'll clean the electrical contact as suggested. Then maybe a new switch. Then digging deeper to the solenoid, where that is located. I started an implant procedure today. Extraction. Bone graft. Now 4 months healing, then the implant. $7000. The switch will surely be less...

 

Thanks for all the advice. I'll let you know what happens.

 

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Cleaning of the lever switch seems to have done the trick. I took the switch off and unplugged the leads. Electrical Cleaner and compressed air. Reassembled. Now...one click squeezing the lever. One click releasing the lever. Doesn't repeat. Thanks all.

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Good, "one click" is all we ever want to hear from a solenoid switch.  All of the components in this situation (the clutch switch, the solenoid itself, even the wiring and connectors) are all very robust items, not known to deteriorate.  So the cleaning will most probably take you well into the future. 

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