franky wrote:I have just purchased a MC18 NSR set up for racing. Was wondering what best set up for filtration for carbs. It came with bare carbs with just an empty air-box sitting on the carbs with no lid on it!

Define "best setup", best setup for what?

The best normal setup for top end power is either an HRC style air tray or just open carbs.

Open air box (i.e. no lid) is a bit of a cheap mans half way house, if you're bothered about keeping stuff out get an air filter (clearly the denser the foam is the more restrictive and the more effective at keeping bits out it will be) and the plate that stops it falling into the carbs (17212-KV3-000) and either a lid with a couple of 2.5cm holes in (the std air box is a restriction) or just use some wire to hold the air filter in place.

It'll make better midrange like that but you'll lose a bit at the top - presuming it's jetted spot on in each case and as it's an '18 that'll be 61-63 bhp which is pretty good.

We saw Andy's '21 pick up a horse just removing his pod filters last year so anything in the way at all is a bad thing when we're talking topend power.

Force feed air has been seen to work well on Bill Limb's '21 as long as the carbs are contained in the airbox, you really shouldn't even run the risk of pressurizing an airbox that does not contain the carbs as well unless you really know what you're doing.
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