a little rough or buzz at 4250-4400 rpm

[navigate40]

Hello!

I am a new Honda owner and new scooter/motorcycle driver.

I have a new 2014 Honda Forza 300. Really love this bike, it feels more like a sport bike than a scoot to me. I am in my 50's and have never ridden before. Just got my motorcycle license a couple months ago. Looked at a lot of bikes, a lot of scoots, read many helpful comments on this board and now, have this great bike.

I lowered the shocks about a week ago, and just hit 500 miles. For the past couple of rides, I have felt this buzz or roughness whenever in this rpm range: 4250-4400.

No sure what it could be. Off the bike, cannot feel anything that might be loose. The buzzing or roughness feels more like it is in the engine, than anything vibrating at that harmonic.

Any advice would be greatly appreciated.

If it helps, I live and ride in SE Florida. Might be a little dusty in spots, near the beach.

Thanks.

John

[Forza 300]

It sounds like your talking about a topic( slight vibration at 68 mph .....anyone) already covered before ,it's the resonance frequency on this scooter others have complained about it .
Don

[navigate40]

Hi Don

Thank you for a quick reply. I thought about that, it certainly could be, I do not know. But, when I have read that, the speed is about what you have mentioned.

At this rpm, my speed is about 35mph.

Could it be the simple resonance freq of the engine? I did not notice it before (I think).

Thanks

John

[Forza 300]

Hi John
Yes most likely it's coming from the engine , a single cylinder, with a larger displacement will vibrate more then a single smaller displacement engine , a lot of engines use a counter weight to minimize the vibration, at idle you will notice a slight vibration this is normal. Then as rpm increases you will get a vibration most have complained at about 65-70 mph this is also normal( resonance frequency) there are ways to minimize this resonance by adding a rubber weight on exhaust,engine,frame,etc depending on what's causing the unwanted resonance, for instance on honda cars if you remouved the front bumper covers the engine would vibrate more that's because the bumper covers are like a rubber weight and shake cancelling the engine vibration , there is also on some honda cars rubber weights in the steering wheel to cancel out engine vibration ( on the forza there are weights on handle bar ends to minimize handlebar vibration)and since it's only a scooter honda didn't think it was necessary to fine tune the whole scooter to be 100% vibration free. Maybe if they get enough complaints they will do something about it. That's the way they work I retired 2 years ago from working on honda cars.

Don

[beegmouse]

I have this exact thing.

It's definitely a resonance. A about 4-4.5K rpm something vibrates like crazy and makes a lot of noise. It almost sounds like a fog horn.

The other topic seems to say its cause by load being put on the baring in the case of the CVT.
It can't be that as there is almost no load at 30mph, and it does it irrespective of engine braking or accelerating or cruising.

The sound is defintly behind me as I ride, I think it's coming from the airbox or fenders as, I can't explain why, but it has a plastic sound to it, not metal, not a ringing. More like a fart.

If anyone else works out whats causing it i'd love to know.

[BRed]

The normal resonance from this bearing is at about 65mph, but at the low speeds you're describing, the clutch bushing is free wheeling in the bearing....
thus the specification to grease it on each removal and the fact that it easily slides in and out of the bearing.

if this rather loose outboard bushing to bearing fit ever became dry or lost its grease somehow, the bushing would like chatter (loudly) at the point where it should be free wheeling and would only get quiet when it finally became loaded and locked to the inner race at high rpm?

I have never heard or experienced any sort of low rpm vibration in the 35mph range, only the 65-70mph one most have noticed and even it becomes less obvious with higher miles.

are these low mileage scoots?

[DioTiAma]

Count me too! But, the resonance is not that loud, always happens@4,400rpm & it is because i replaced the back tire with a wider one (150/70 - 13 M/C 64S) without balancing it (didn't have this before the tire replacement). With my lady on board (53kg), it is NOT vibrating at all. So, at least for my case, i know why i have this mild resonance. Currently 14,000km on the scooter.

[navigate40]

Thank you for the replies, these are very helpful.

I bought my bike used, with only 222 miles. Incredible deal (fuel pump was replaced, and it came with an extended warranty).

It now has 555 miles.

The rear tire WAS replaced. The new one is a Dunlop, 140/70 13 MC. I think it has been balanced (one weight on it) and is in spec.

The buzz is pretty low frequency and not really audible. I feel it more than hear it. It is definitely below and slightly behind me as I sit. It is fairly subtle, but noticeable.

I have read some comments about the clutch or transmission before. I thought the clutch was a dry clutch and should not be lubed?

Really love this bike. Planning on installing the tall Honda windshield.

Appreciate all replies.

Thanks

John

[you you]

Thank you for the replies, these are very helpful.

I bought my bike used, with only 222 miles. Incredible deal (fuel pump was replaced, and it came with an extended warranty).

It now has 555 miles.

The rear tire WAS replaced. The new one is a Dunlop, 140/70 13 MC. I think it has been balanced (one weight on it) and is in spec.

The buzz is pretty low frequency and not really audible. I feel it more than hear it. It is definitely below and slightly behind me as I sit. It is fairly subtle, but noticeable.

I have read some comments about the clutch or transmission before. I thought the clutch was a dry clutch and should not be lubed?

Really love this bike. Planning on installing the tall Honda windshield.

Appreciate all replies.

Thanks

John

See how the second 300 miles go?

[beegmouse]

Clutch is dry, but unlike small CVTs the Clutch axle is supported by an extra baring embedded in the Transmission case. Than could be loose..

I'll open mine up and have a look tomorrow, but mine sounds a little like a vuvuzela, I'm still thinking something plastic resonating.

[navigate40]

Hi Beegmouse

Appreciate the response. So, I assume this is just a normal resonance and I should leave it alone. It does not bother me, just curious.

This is my first bike.

Thanks

John

[beegmouse]

An update on this.

A third Bolt on the rear numberplate reduced the noise significantly. Still Buzzes, but now its not as loud as the engine.

[DioTiAma]

Hello there guys. Try these things (all together or one each time): 1) remove the tools from under the saddle, 2) remove the licence plate & 3) replace these two O-Rings (91301-K04-930), 4) lock the saddle when driving (i rarely do it so i don't use the button that much or if i need something during a ride i won't have to turn off the scooter in order to get it -Honda, you need a few slaps for this flaw & for the gas spring too-). Beside all these, if your rear tire is replaced with a wider one, there is a great chance that this is the reason of the resonance@4.400 r.p.m.!

[waspmike]

If your tire has been replaced with a wider one? Have you looked at the air inlet from the airbox to the throttlebody? Is it very close or touching?

[DioTiAma]

Neither. Irrelevant anyway Mike. If it was touching, it would produce noise (in all revs spectrum), not resonance (in certain revs).

[davenowherejones]

If your tire has been replaced with a wider one? Have you looked at the air inlet from the airbox to the throttlebody? Is it very close or touching?

This got me curious so I looked at my Forza with a Michelin City Grip 150/70-13 on the rear. There is about 1/4 inch clearance when the bike is on the centre stand. I wonder if this clearance changes at speed? Doesn't seem to be rubbing anywhere.

The Forza rides nice with the Michelin but not any better than the Scootsmart. About the same.

Snowing on the mountains right now. Warm in the house. Going to do absolutely nothing today!!!

[waspmike]

Neither. Irrelevant anyway Mike. If it was touching, it would produce noise (in all revs spectrum), not resonance (in certain revs).

What speed is 4250-4400 rpm? Just curious.

[waspmike]

Snowing on the mountains right now. Warm in the house. Going to do absolutely nothing today!!!

Keep the faith and live in hope? Eh! Lest you end up in Hells Gate. It is not the Enderby of the world!

[davenowherejones]

Snowing on the mountains right now. Warm in the house. Going to do absolutely nothing today!!!

Keep the faith and live in hope? Eh! Lest you end up in Hells Gate. It is not the Enderby of the world!

I have been at Hells Gate when it was frozen over. And I have the pictures to prove it. The lift, not the water.

[waspmike]

Neither. Irrelevant anyway Mike. If it was touching, it would produce noise (in all revs spectrum), not resonance (in certain revs).

Just noticed the aftermarket shocks do you have stock or aftermarket bushings? maybe they are urethane not "normal" rubber are stiffer than stock and are transfering vibrations from the engine.