Odd noise at precisely 3500 revs

[JLW]

The bike is going great and I’ve nearly done 300 miles.

There is just one annoying aspect that I hope someone might be able to assist with -

As you accelerate the bike and it hits precisely 3500 revs, there is annoying scratchy raspy buzzy vibration sound that lasts a fraction of a second, then goes as you pass 3500 revs. Sound a bit like someone receiving an electric shock in a cartoon.

The noise only occurs as you accelerate through 3500 revs and not as you are decelerating down through 3500 revs.

I can’t pinpoint where it comes from, and wasn’t sure if it was actually something in my helmet resonating, or electrical interference with my Bluetooth intercom, but changed helmets to another make of helmet and the sound still occurs. (And also occurs with the intercom off)

I’ve also tried tightening the fairing and screen bolts.

As I’m currently rev limited to 4000 revs during break in, I pass the 3500 rev spot very frequently and the noise is starting to drive me potty!

Any assistance would be gratefully received.

[JustinP]

Can you record it? Does it happen in every gear?

[keith zx]

I found that the sx h2 engine makes some rather strange noises on and off the throttle , engine note seems to change , in fact when I first test rode one I thought it felt a bit ruff !!! compared to my sx 1000, that's un till you start getting it wound on a bit .

[PhukDD]

I would not worry about it. Once you are ready for full throttle, you will only ever be at that rpm for a millisecond.

[danham]

I rarely ride without ear plugs. The first time I rode my SE without them, I thought the cam and supercharger chains were trying to thrash their way out of the engine. It’s not a Swiss watch, to put it mildly. Combined with some slight surging at low engine speeds and small throttle opening (courtesy of the stock fuel/timing map?), our engines can make some messy noises.

-dan

[PhukDD]

I rarely ride without ear plugs. The first time I rode my SE without them, I thought the cam and supercharger chains were trying to thrash their way out of the engine. It’s not a Swiss watch, to put it mildly. Combined with some slight surging at low engine speeds and small throttle opening (courtesy of the stock fuel/timing map?), our engines can make some messy noises.

-dan

You can fix that surging dan.

[danham]

You can fix that surging dan.

Yup, thanks. If I go that route it will def be with Dave.

-dan

[JustinP]

I rarely ride without ear plugs. The first time I rode my SE without them, I thought the cam and supercharger chains were trying to thrash their way out of the engine. It’s not a Swiss watch, to put it mildly. Combined with some slight surging at low engine speeds and small throttle opening (courtesy of the stock fuel/timing map?), our engines can make some messy noises.

-dan

I ran around the block yesterday without earplugs, and I can confirm this lol.

[JLW]

Haven’t been able to record the sound above the wind noise. However I did a test and it is noticeable in all gears except first (passes 3500 revs too quickly)
It is especially prominent in 4th gear.
The noise is absent when increasing the revs past 3500 whilst the bike is stationary in neutral.

[JustinP]

So it only happens when the engine under load. Sounds like something is loose and vibrating at a specific frequency. Check motor mounts, exhaust hanger/shield, clutch springs/nut etc.