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Chirping Noise When Opening Throttle


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Took my bike out for a quick ride to the shops last night (we're under another COVID lockdown in England, so took the opportunity to combine a quick ride with a trip to the supermarket for essentials).

 

Bike ran fine on the 10 minute ride the the supermarket. Started the bike to ride back home and let it idle whilst putting my helmet and gloves on (I'd only been there 10 mins so bike still warm) - thought it was idling a bit slow and sounded a bit uneven, but it responded normally to a quick blip of the throttle so I thought nothing of it.

 

Got on the bike and edged out of my parking space - as soon as I opened the throttle and moved forward I heard a chirping noise somewhere around the clocks/tank area - similar to the noise a 1990s car alarm makes when arming/disarming. 

 

I stopped and moved off again and the same thing happened. I rode home gently and every time I opened the throttle even just slightly I heard the same noise. I thought the bike felt sluggish and unresponsive, almost as if it was being starved of air or fuel - but I was riding very gently  with low revs and small throttle openings on account of the greasy roads and the bike is always a bit sluggish when ridden like this - and I was anxious because of this strange noise and just wanted to get the bike home - so it's possible I imagined the sluggishness.

 

I got home without incident - left the bike running in neural and worked the throttle a few times - heard same noise every time I opened the throttle even slightly, so probably not a clutch or drive train issue. Thought it might be a throttle cable or linkage issue so shut down and worked the throttle a few times, no noise - so probably not that.

 

I let the bike stand for a few minutes - started up again and rode carefully round the block, the noise had gone and the bike felt fine. Decided to risk a quick 5 mile ride along the bit of urban dual carriageway that runs through town riding at constant 40 to 50 few minutes and accelerated hard a few times - bike felt normal and didn't hear the noise again. Rode the bike arounf the block from cold for a couple of minutes this morning and didn't hear the noise and it feels fine.

 

Had a look at old threads on here and elsewhere last night. Found a thread with a similar issue and the solenoid to either the Flapper or PAIR valve seemed to be the likely issue (thread linked below). Also found a number of references on both car and bike forums suggesting that throttle bodies can make these sort of noises when the butterfly valves don't close fully.

 

 

The obvious next step is to disconnect the Flapper and PAIR solenoids one at a time if the issue does recur - but I'd be grateful for any thoughts/advice.

 

      

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Would first try the variable intake (Flapper) solenoid first, just unplug the electrical connector, see how it goes. A dirty clutch switch can cause the solenoid to make strange noises.

 

Also remove the air filter and inspect the area, make sure everything looks normal in the airbox.

 

The other issue which causes more of a clatter sound is a faulty CCT (cam chain tensioner).

Good luck keep us posted with what you find.

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Thanks. 

 

Have ridden the bike a few times since and the circumstances under which I hear this noise are now consistent and predictable. It happens when moving the throttle from closed to very slightly open either at idle or at very low revs either when stationary or trundling along in traffic. It doesn't happen when the bike is cold - only when it's warmed up sufficiently for the revs to drop to normal "warmed up" idle speed. I don't hear the noise when on the open road using more revs and bigger throttle openings and open road performance seems normal. I'm still undecided if the bike is more sluggish than usual when trundling along in heavy traffic.

 

It's an almost electronic sounding chirp, not a clatter or rattle - so don't think it's a cam tensioner. Also does not correlate with using the clutch - only with throttle movements. Noise is definitely from the tank area - so increasingly suspect the variable intake solenoid. Will have some time this weekend to play with the bike, so will disconnect and report back.

 

Thanks again.

 

 

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10 hours ago, BlackheathMatt said:

Have ridden the bike a few times since and the circumstances under which I hear this noise are now consistent and predictable. It happens when moving the throttle from closed to very slightly open either at idle or at very low revs either when stationary or trundling along in traffic. It doesn't happen when the bike is cold - only when it's warmed up sufficiently for the revs to drop to normal "warmed up" idle speed. I don't hear the noise when on the open road using more revs and bigger throttle openings and open road performance seems normal. I'm still undecided if the bike is more sluggish than usual when trundling along in heavy traffic.

What you're describing is basically when the flapper is directed by the ECM to close during low rpm. The flapper is in the normally open state during mid to high rpm settings.

So I'm sure what you're hearing is to do with this system and electrically unplugging the control solenoid should confirm this for you. Could even be a squeeky/noisy vacuum diaphragm. It's also a system you can do without.

Cheers

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Thanks once again.

 

Apologies for potentially dumb question - I'm aware that many choose to disable the flapper valve by blanking off the sensor tube. If I disable it by disconnecting the solenoid - will the flapper valve default to the open position ?

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7 hours ago, BlackheathMatt said:

Thanks once again.

 

Apologies for potentially dumb question - I'm aware that many choose to disable the flapper valve by blanking off the sensor tube. If I disable it by disconnecting the solenoid - will the flapper valve default to the open position ?

Correct. Without any vacuum applied to the diaphragm it is spring loaded to the open position. When the control solenoid is energized it allows vacuum to act on the diaphragm pulling the flapper to the closed position.

The other option is to simply pull the vacuum hose off the flapper diaphragm and plug/seal the vacuum hose. The flapper will be fully open.

I've used the end of a drill just the right size to plug the hose in the past.

Guess what you're trying to isolate is either a noisy diaphragm or a noisy solenoid.

 

Just for info - I've removed all the hardware of this system on my 8gen mainly to just free up space under the fuel tank. Honda has also removed this system from the 2017 8gen. My bike has been running fine (subjectively) in all aspects since removing it some 25,000kms ago.

 

Cheers and let's know what you find.

 

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Not really - but thanks for asking.

 

Weather has been terrible in the UK for last couple of weeks - and we're still under lockdown for the next 10 days - so haven't ridden much. 

 

Irritatingly the last time I did ride the bike I didn't hear the noise. Have however familiarised myself with unplugging and reconnecting the solenoid - so next time it happens I can quickly disconnect it know if this is the issue. 

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