Why do OCC bikes make that noise?

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canuckerjay · Mon Mar 24, 2008 11:50 am

Okay -- for someone more technically inclined than I:

I used to like American Chopper (like a lot of other people) and as the years worn on, so did the show. Now it's more about them socially as opposed to the mechanix.

But I digress. . .

Over the years, on the occasion where I watch a bike finally come to the point of test ride, I've noticed that many of them make a high pitched 'chirp' noise. The throaty exhaust note is still there, but it sounds like a budgie is desperatly trying to escape a cylinder head.

Just wondering if anyone knows why this is?

#2 Unread post by **fireguzzi** » Mon Mar 24, 2008 1:15 pm

Poorly lined up primary belt? Shitty chromed brake rotors. Squeaky chromed painted themed spinners that were made in house by a bunch of horses bottoms. incorrect tolerances inside the unlubed five thousand cubic inch s&s motor with some crazy a$$ air intake that whistles.
Most likely though it is paulies whiney a$$ in the background yellin at his daddy.

SHADOW1100T · Mon Mar 24, 2008 7:14 pm

Beleive it or not the exhaust can make that sound, it's caused by the pressure wave of sound creating a vacuum and sucking in air, had a flat tracker one time that sounded like it had a bunch of birds liveing in the muffs.

#4 Unread post by **Wrider** » Mon Mar 24, 2008 8:42 pm

I'll agree with FireGuzzi... Although I think that high pitched chirp you're hearing is the air intake on the motors... When you've got that big of a motor running on two intake valves per cylinder it's gonna try to take in more air than it can...
Wrider