My Bike is "Rocking" me...

[gogobert]

Hello,

I have an issue with my Forza 2014.
When driving at even speed (just giving enough gas to maintain the speed) between 35kmh - ~80kmh, and when slowing down from ¨100kmh and engine-breaking, there is a firm but very obvious “rocking” behavior (not jumping) on the bike. I feel that the whole bike is moving up and down about 1cm so to say. The frequency of this ‘rocking’ is perhaps about 3-4 Hz at 35kmh, and increases all the way up to around 80kmh, then it kind of disappears. If that is due to the ‘rocking’ frequency gets so high when the speed increases or what I cannot really say, what I can say is that it’s not at all as significant during higher speeds. and really not below 30kmh either.

I am not that an experienced scooter driver, but this behavior was definitely NOT on the PCX125 I had, so it doesn’t seem like a ‘feature’ for Honda scooters.

Does anyone recognize this or have any suggestions to why this could appear? else than too hard/soft suspension, too high/low air pressure in the tires, cause those I have already tried to change with no change at all. I am completely lost in this, but my thinking is that It definitely has something to do with something revolving, either the wheels are not circular? or something in the transmission/engine/belt-drive is off-axis? Could something like that make this behavior?

I actually had it on service for the fuel-pump exchange and the shop took a look at this problem also, but as usual, they couldn’t really say anything and just checked the obvious things and took a short test-drive (not when I was present of course) and just… - “well, I couldn’t fell any problems”. Duh! Why does it always feel like they really don’t listen?

Anyway, I would really appreciate any advices, just to give a hint to Honda when I have to try and explain this again and make them take this on seriously…I mean, the bike is almost brand new, I have ran it only for 1800km and to be honest, I have felt this almost from the very first time I drove it out of the shop.

BR, Thomas

[iceman]

I'd imagine dealers rarely want to deal with warranty problems as Honda may not look knidly on dealers that pass on too many 'free' warranty fix issues, and also they would have to spend lots of time investigating and only get a fraction of the man hours back from Honda.

[gn2]

Could be one or both wheels out of balance.

[waspmike]

Does it do the same thing if you run it on the stand?

[gogobert]

Just thought of that myself this morning, so, I will try that tonight.
If it's still there, then it has to be something with the engine/transmission...

[gogobert]

Could be one or both wheels out of balance.

Yes, but shouldn't the 'rocking' be abit faster then?

a 14 inch wheel should turn about 9-10 times around its axis per second if the speed is 35kmh = 10m/s - the frequency then should be much faster on the rocking if its correlated to each 'lap' so to say...or do I have bad luck when doing the maths?

[gn2]

Wouldn't hurt to have them balanced and see what happens.

[tbln930]

Is it rolling too?

[gogobert]

well , dunno if a scooter is both...

[gogobert]

Ok, now I have driven it on the stand, all the wayy up to 100kmh, and no such rocking whatsoever, just normal vibrations.

But when I looked at the backwheel while running, it looks abit unblanced or askew, is that the word?

Anyway, time to take it to the dealer and force him to take a testride either with me or by himself. I cannot go on like this...

[gn2]

Tyre might not be seated properly.

[BRed]

It's possible you're just feeling the Forza's swinging link suspension....
the engine/cvt is mounted to the frame via a 3 or 4 piece swinging link...
this is not a normal hinge.

this is to dampen vibration and does a good job of it, but during hard acceleration/deceleration, the rear wheel can move fore/aft a tiny bit relative to the front wheel, courtesy of the swinging link engine mount

If this is what you're feeling, it feels strange at first, but it doesn't impair handling and you'll get use to it very fast.

[gogobert]

nah, cannot really think that this could be a normal, it much to significant and irritating.
I kinda lean towards that something is fishy with my back wheel...

[j.d.b.]

Really going to need to put tech on it. I doubt we're going to fix it, here. Will it do this rocking with two people on it? That would make it easier to point out, otherwise, try to explain to the tech what/where he's looking for. Speed, load, etc. So the the test ride is fruitful. If it's as pronounced as your describing, tuning the tech into the problem shouldn't be difficult. It sounds like a matter of whether your tech is interested.

[Kermit]

I agree with the others...sounds like things are out of balance. Could be the tire or the wheel.

I had an annoying "bounce" in one of my car tires, even on a brand new, smooth-as-silk highway. Tire place replaced it for free, since it was a relatively new tire they installed. That didn't help. They looked at it again, more closely this time, and it turned out to be my wheel, which was slightly bent (okay, I hit a curb). They replaced the wheel and the tire, and everything was smooth again.

[gogobert]

I dunno, but this is how my back wheel is 'moving' when running on the stand....do You think it can cause this 'rocking' behaviour?

https://youtu.be/7Uj7tQJ3E8c


/

[yak]

I watched your video. It doesn't look like the tire is moving enuf to cause a rocking motion when you ride.

[gn2]

Video is inconclusive because its a short clip, only shows one side of the wheel/tyre at an oblique angle and the camera appears to be moving.

[gogobert]

Video is inconclusive because its a short clip, only shows one side of the wheel/tyre at an oblique angle and the camera appears to be moving.

well, that was the best I could do, I just wanted someone experienced to have a look and comment...it looks worse in real life (I think at least)

[SteveP]

I dunno, but this is how my back wheel is 'moving' when running on the stand....do You think it can cause this 'rocking' behaviour?

https://youtu.be/7Uj7tQJ3E8c


/

Looks "ok" in the video, but maybe under load there could be a soft or hard area in the tire you can't see in the video. ??? Tire appears mounted on the rim correctly (centered), at least on the side showing. Have you tried different air pressure to see if that makes a difference? Any drag or tight spot in the brakes that might cause this? The rear wheel won't spin real freely due to drag in the transmission, and the disc brakes will also drag slightly. There might also be a out of round, off center condition in either transmission pulleys.