Clattering upon deceleration between 10-15 mph

[SlothNast]

Hi all,

Definitely curious on what your thoughts are in regards to this. I am fairly new to the PCX, and have a 2011 PCX125 with just under 2000 miles on it. Everything seems to work great, service was performed at ~600 mi, and its only until recently I discovered this problem.

Upon slowing down or braking, I typically try to balance engine-braking with actual braking in a way that allows my brakes to have a reasonable lifetime, while also not putting too much stress on the engine when letting off the throttle (i.e. letting off the throttle on a descent). Something I've noticed is that when I am primarily engine-braking between 10-15 mph, there is a rattling from under the seat that I can quite easily hear and slightly feel. There's definitely a sweet spot at around maybe 13 mph, because any slower/faster, it goes away. Also, there is no noise when I accelerate through 13 mph. I've seen a few posts on this, and sense a mixed opinion between this being 'normal' behavior or something to do with clutch/bearings. Just curious if this is indeed normal (and why), or if it deserves some more investigating.

Any word on this would be very helpful and greatly appreciated!

Thanks

[gn2]

It could be the centrifugal clutch disengaging.
As you slow down there will be a set speed at which the centrifugal force on the shoes is not enough to keep them on the clutch drum.
Usually if you decelerate using engine braking only you can feel a slight surge as the clutch lets go.
If your clutch is not releasing smoothly, it might be the cause.

[waspmike]

I'm going for the variator being at the furthest point apart (lowest gear) so the weights are no long trapped in their track between the ramp plate so they are free to rattle.

Just a note on riding style. Police in UK, where there are mostly manual transmissions, are taught to slowdown using predominantly the brakes, not the engine. Then to select a lower gear and accelerate away. As brakes are cheaper to repair than engines.

[gn2]

What UK police drivers are trained not to do in manual transmission cars is pretty irrelevant for deciding how to ride a CVT scooter.
You can't over-rev a CVT scooter by closing the throttle.

[Alibally]

I get something similar. It sounds like the belt vibrating.

[maddiedog]

Just to make sure, given the age and your PCX's mileage, has service been maintained?

The most likely cause is clutch engagement / disengagement as everyone else has suggested, but I've heard of poorly maintained PCXes (that have skipped the first maintenance interval after years of low use) having the actual engine juddering from sludge.

Keep in mind that service intervals are both based on mileage and age. If your 2011 still hasn't had an oil change or it's been a year or so since the last one, you should go get an oil change and service just in case.

[SlothNast]

Thanks everyone for the suggestions. I'll probably take it to get checked out at the local Honda garage and get an oil change and clutch inspection. The first service was done at 850 miles in 2012 and the scooter is currently at 1850 miles three years later. I don't believe any oil change was performed in the meantime, as it definitely was only ridden occasionally.

If the problem is clutch engagement related, can I expect a relatively steep bill? Not sure I can cover this at the moment but I definitely want to diagnosis this and at least swap the oil.

Thanks guys!

[gn2]

You can easily change the oil yourself, its not a hard job, do that first and see how you get on.

[SlothNast]

A fresh quart of hp4m did the trick from what I can tell. Thanks guys!

[honkerman]

Sure is amazing what a little clean oil can do.

[iceman]

So bad oil or lack of was to blame for the chattering - when you changed it was there much oil in the engine?

[SlothNast]

The amount of oil was just fine. However, it had lost all of its viscosity and was near black.

[SlothNast]

Update:

After some time, I have realized that the characteristic noise still persists even after the oil change. However, I have learned more about the noise.

1) It sounds like plastic - plastic contact
2) It occurs under my feet
3) When on the center stand, at similar speed, the noise ceases (but the whole bike shakes)
4) The bike took a very light drop from the last owner, on the front right side there are light scratches

So my theory is that there is some loose piece of plastic that resonates at around 12-13 mph under the floor from the drop. Does anyone else's bike resonate at around this speed? And if so, any guesses on what the loose piece could be? It'll be a while before I get access to under the floorboard.

Thanks mates!

[iceman]

Not got the service manual with me but I wonder if the underside panel comes off without the need to remove any top-side paneling? (there is a dirt block / grime provention oblong bit of plastic on the bottom side of the bike covering the engine area - maybe it's something rattling just under that cover.

[maddiedog]

Iceman, it does. Check out the howto here: http://hondapcx.org/viewtopic.php?f=3&t=2630

[SlothNast]

Unfortunately after inspecting the bottom fenders the sound persists! Grr

The noise seems sort of like a rubbing or grinding of plastic, rather than a rattling noise. Will have to just wait and listen until I get the tools and ambition to further diagnose and inspect.

Iceman, it does. Check out the howto here: http://hondapcx.org/viewtopic.php?f=3&t=2630

Great walk through maddiedog!! And thanks iceman I'm confident the noise comes from right under the panel.

[TeeJayDee]

I have also have a 2011 PCX 125, albeit with 15,000 miles on it, and I also get the infamous chattering noise at the 10-15 mph range. But mine is definitely is coming from the clutch/variator area. Like yourself, when it's on the stand, the noise is not there, so I can only hear it when I am actually riding it. I did a lot of research on it and found many informed reasons as to the cause, one of which is a suspected fault with the clutch bearing. I was fortunate when I bought my PCX as the mature previous owner did tell me about it and then gave me the original variator, clutch and belt. He had obviously spent loads also chasing this noise with no success. So when it came to diagnosing it myself, I could discount many of the theories being offered. Now that I have ridden it for close on 3,000 miles myself, the noise is still there and it doesn't affect the bike one jot. In fact, I have just gotten used to it. Out of all the theories I have read, the one I go with is that it is something to do with the centrifugal force of the belt, whereby it goes from using the top to the bottom (or vice versa) at different speeds. The chattering noise is just a change in where the belt is being pulled from. All-in-all, just a 'normal' characteristic of the 1st edition PCX.

[Shmalex]

So I've noticed I'm not the first one to hear this noise. I checked for my valve clearance today BTW, though it was the incorrect clearance that's causing the sound, after adjusting to the correct specifications it still kept knocking. I'll attach the clip of the sound I recorded with my phone. I was recording it without body plastic. Tell me if its the same sound that everyone is complaints about. You will hear it at the very end of the clip.
https://drive.google.com/file/d/0Bxg1y6 ... cslist_api

[Seph]

Mine went in for its service Tuesday, since then I've had a humming or vibrating noise when I hit 25mph until around 35mph. I called they said if I'm concerned to go back down.

[iceman]

Mine went in for its service Tuesday, since then I've had a humming or vibrating noise when I hit 25mph until around 35mph. I called they said if I'm concerned to go back down.

Sounds very much like it's a harmonic resonance issue and depends on how the panels fit together when assembled - sometimes people are lucky, other times the panel design and how they fix together just happens to be centered around the harmonic point give or take a few mph.