Vortex ROK GP - Airbox filtration?

New to karting - I purchased a used Intrepid Cruiser MS3 with a Vortex ROK GP motor. I was surprised to see that there was no filter in the airbox / intake silencer.

When I asked at the track they told me to just keep the inside of the airbox clean, especially if I go off the track.

Not running a filter is really foreigh to me. I don’t want to damage the motor with it sucking in debris. Is it true these motors use just the intake silencer without a filter? Is there an aftermarket filter option that will give me a little more piece of mind without creating performance issues?



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I use one of these https://www.fastech-racing.com/rlv-airbox-filter.html

Not sure if it robs any horsepower, but like you, I was hesitant to run without one.

Hopefully others will chime in and give their thoughts…

Hi Allen,

Do you use this filter in place of the airbox, or can this filter be installed inside of the airbox?


Thank you!

Inside the airbox. It pretty much replaces the rubber boots that comes with the airbox.

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Lots of people run a filter like the above on a variety of engines. A nice way to ensure you don’t suck up dirt or something in an off-track excursion.


I’ve always found it odd that Rok supplies its motors without foam filters. If you are in a bind without a filter, smear some grease in the bottom of the airbox and around the red trumpet-thingy openings. This will help trap some dirt or dust before it gets sucked into your engine.

@Christian_Fox, do you know if the filters are an accessory? I can’t seem to find much on the web about filters for the Vortex motors.

I do not normally run an air filter on our Rok shifter unless the track is very dirty. I use grease inside of the intake silencer to trap bigger particles/stones. I also use a light coating of white lithium on the trumpets- this gives you a good idea of how dirty the track actually is and catches some particles as well. Running with a filter is only a tenth or two slower with the shifter but I’m not sure about the GP package. Maybe practice with a filter and race without? ikg_0290


Rok (Arrow) does not make an OEM piece, so guys just use a generic one like the one referenced by Allen.

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Thanks! My trumpets don’t have the plastic mesh covers on their either. I guess that would stop larger particles.

I’ll have to source the filter above in Canada and give it a go. The filter will give me piece of mind when I’m just lapping around the track.

One other question, I see some sites offering two different lengths of trumpets. Does this tune the inbox in any way or is it just different lengths trumpets for different size airboxes?

I appreciate all the feedback!

Do anything need to be changed on the carburettor when using filters ? I’m thinking jets etc ?

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We are using the internal filter “bag” from the Iame X30, their part # in their diagram is 221. At our dusty track in the desert last January at the Challenge of the Americas, drivers were destroying engines, literally in one day, without a filter element in the air box.

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This one ?? And do you put the filter part, inside the box ?? https://www.kartpartsuk.com/products/iame-x30-spare-parts/iame-x30-air-box/iame-x30-foam-filter

Hi Brian – The part your supplier shows appears to be correct, and, yes, you put it in the air box. However, allow me to hedge just a bit. I am new to the VLR 100 as I’ve only had Rotax engines on my karts until now. My VLR 100 is new and not even broken in – corona virus, track closing, etc. I have purchased an Iame foam filter which is sitting on my desk as I type this. It carries Iame part # 10751-A.

However, what I said in my previous post is correct. To amplify, I wrenched for a friend this January who races in TAG Masters; he is literally a rocket scientist and has 10 karts of his own plus more spare parts and tools than most kart shops. He is the one who discovered the absence of a filter element in his ROK engine inlet box and, after some research, bought and successfully used, the Iame filter (the same one that I have now purchased).

Until I have personally put it in my air box and fitted it up to the inlet of the Tillotson carb, I cannot be 100% sure it will fit my VLR 100 as it did my friend’s ROK GP – but I’m 99% sure it will. The picture in the kartpartsuk link you sent appears to be at an angle that doesn’t show the 30 degree (+ or - ) bend on the rubber neck that fits around the card inlet. But everything else looks correct, including the price. Hope this helps – I can tell you I will not run my engine without such a filter .

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For better or worse, it’s not uncommon for karts to be run without air filters. It’s probably not a coincidence that the lowest maintenance engines run one though (Off the top of my head).

It’s possible that running one inside the airbox might affect partial throttle response as there’s an aspect of resonance from the airbox.

I do like the idea of running the KA filter if it works. One thing to consider is the ruleset may not allow the filter, so check on that before using one in competition.

Since the box is mainly for mitigating intake noise, which is noise, which is apparently considered anathema to human existence according to CC&R 'hoods everywhere, I don’t see it becoming optional.

Brian – Put the filter in the air box for my VLR 100 yesterday. The fit-up was 100% problem free, and I started the engine for the first time without any issues. That should close the loop.


I have been running the RLV filter with the angled rubber boot without problems in my ROK GP.

UNI RLV Airbox Filter

The angled boot replaces the standard boot in the factory airbox.

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