Whistling moise on part throttle?

I've noticed that occasionally my 11 520 RS makes a slight whistling sound on part throttle. It's most noticable on the road, likely because the noise of rock and sand is loader than the whistle. I' ve checked to make sure the air box is sealed. On a side note the Datsun I race has FCR flat slide carbs on it and I do notice the similar kind of whistle but it has no air box (velocity stacks only) Anyone else notice this noise?


Yup, it is the carb working normally. 

Yup, it is the carb working normally.


I like that sound!! 

I'm wondering if it isn't simply intake noise. I had an older 'berg (pre-EFI) that sounded like there was a bird under the seat... when I first got it, it was driving me nuts. Then, I realized that's just the sound of the intake, I started to like it. It was really loud, too.

I have the same bike (roughly)  as you- 2010 RR, but I'm not sure if I've noticed it. 

I had an 04 400exc that whistled like crazy. I didn't worry about it.

Thanks guys, as I mentioned the Datsun does this as well and I was just making sure it was normal for the bike.  I'm a big fan of flat slide carbs, the ones on the car are the 45 degree down draft type and they're absolute works of art...................the bonus for my Beta is I have loads of jets.............which of course I've had no need for on the Beta.




When it STOPS whistling, you replace the slide plate seal....cause it has failed.

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