Not sure if I'm posting in the right area with this one, but here goes!

My MC21 is fitted with the bottom of the original airbox, but with the top removed and just some filter material stretched over it. Rather than control any airflow, I think all it is doing is stopping any crap* getting sucked into the carbs. It also looks bloody awful, and isn't actually fixed to anything, it just sits there on top of the carbs between the frame rails! I'm considering junking it and running open carbs, or waiting for one of the airboxes that Andy is getting made up.

What are the benefits (apart from the obvious one of increased airflow) of running open carbs on my race bike, and would there be any negatives?

I would like to run one of Dans pressurised airboxes, but I'm having to watch the pennies at the moment so have ruled it out (for now!)

* technical term.
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Last edited by DifferentStrokes on Mon Sep 28, 2009 9:58 pm; edited 2 times in total

I went to open carbs before xmas and haven't had to deal with many negatives! Once I got the jetting sorted it's been pretty much plain sailing from there!

I'm running twinair foam filters and they seem to work great.

Open carbs get my vote for sounding great as well

Hi ,

with open carbs you have a chance that grit from the rear wheel can get flung into the carbs causing caos ! Put a rear hugger on and it will help prevent dirt from entering your carbs .

Neal

The theory is that running open carbs will result in more peak HP and less torque. There is a big risk of UFO's going into your engine. My bike made 73.2HP with open carbs and now, with the HRC airbox it feels a lot more tame. I would sugest high flow pods as Dan (DifferentStrokes) recommends. Does anyone else know more about the intake air volume theory?????????

Deon wrote:
Does anyone else know more about the intake air volume theory?????????

Yeah... the louder it is, the better it is!
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That's the difference between an airbox (no lid, just the box and a proper high flow filter lock wired on) and open carbs. The loss of power between 10 and 11 probably more than canceling out the gain further up.

To be honest I though that it felt best with the lid (with and a couple of holes in) on, a thought confirmed when I rode my '28 racebike back in that format before I sold it the other day.
In fact it was that good I'm going to put a wanted for an '18 airbox in the classifieds in a min.

On the other hand, the fact the box isn't there (and in the way) might encourage you to jet the bike correctly, thus getting the power back where it should be
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