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Continuously Variable Transmission for Karts- Makes You Faster and makes Your Motor Last Longer!

This CVT for karts test has to be one of the most unique, and interesting tests I have ever done. From the outset the CVT does weird things with your brain

Your foot is to the floor, and you can feel the kart accelerate (and does it accelerate hard), but the engine is keeping a constant note at 11,500rpm (as you can hear on the video). You definitely need a few laps to get your head in order.

The CVT is such a unique product to karting, and the way it works on a kart is magical. The guys from CV Racing have really done a great job with creating this product. Check the video to see the system working with the kart on the stand!




Continuously Variable Transmission for karts

How it works for Dummies

Ok, I'm not technically astute, but I'll give a brief explanation of how this thing works. Right the main benefit is that the CVT makes sure that the kart is always running at the right gear ratio. So, it eliminates the problem of needing a large rear sprcket on a twisty circuit, or needing a small rear sprocket on a fast circuit... the CVT automatically adjusts itself to what you need!!

It defeats the problem of conventional karts where you need to fit a sprocket to give the overall best performance. So for example you would fit a small rear sprocket at shennington to take advantage of the long straights, but because shenny also has hairpins the kart will struggle to accelerate out of the hairpins. The CVT defeats this problem because when accelerating from a hairpin it acts like it has a huge rear sprocket, and when you get on the straight it acts like it has a tiny rear sprocket....perfect!

How does it do it.

The CVT has conical shafts on the axle and crank which squeeze the belt drive and continuously change the gear ratio to match the situation you are driving in, thats as much as I dare say, my advice is to look at the video and see for yourself!

Driving the CVT for Karts

The first session out was definitely a feeler session. What got me most was the pull out of the corners. The bottom end of a Rotax Max is famous for being non existent, but with the Continuously Variable Transmission it's a whole different kettle of fish. The accelerator is like an on/off switch. You put your foot down, and bam POWER! That’s the idea of a CVT, it can utilize the full power of an engine at all times, from 0mph upwards.

Once you get used to it, you start to realise how much more inherently quicker it is that your standard chain and sprocket drive. Out of the corners it’s clearly quicker than a standard Rotax Max. Unfortunately there
weren’t many other Rotax karts out there on the circuit to tag along to compare speeds. But when I did have a drag up the hill at Whilton against a standard Rotax Max there was no comparison - the CVT was quicker. That is backed up by the times of the CVT karts at the Open Endurance Championship at Dayton Milton Keynes UK where the CVT teams where about 1 second quicker than the standard Rotax Max karts on Kartline tyres.

The CVT did require me to change my throttle control, and it’s all about faith. Once I had got settled into driving the kart I started to get my braking sorted, I could then concentrate on throttle control. The general
idea with 2 stroke karts is to blend the throttle in as you come of the brakes nice and progressively! But the Continuously Variable Transmission does something very special. It acts as a traction control system. So as the wheels spin, the Constinuously Variable Transmission changes its ratio and stops the wheel spin. This is where the faith part comes in. You can actually bury the throttle 6 feet under and prey and it will stick, well, hopefully, and it does! I only managed to master this once or twice, but it worked! Obviously the CVT in the wet would be even more rapid with the system working like that!

As I had a few more sessions with the kart I started to get used to how the system worked, and how it felt, and I really started to enjoy myself. I think Steve (CV Racing) was a little worried after the first session when I
pulled in looking bemused, and bewildered. But I can assure him that was through amazement.

As I progressed through my last laps my neck started to go. The sticky new Vega’s had finally caught up with me. And it was the pull out of corners that got me also. I was trying to put my head looking down so I looked good for the camera, but as I came out of the corner I could feel my head pulling back. So maybe that didn’t looked to good on my part. That just shows the pull of the Continuously Variable Transmission system on a Rotax Max kart.

Driving a CVT is a totally unique experience. It’s like it’s from another universe. And one of the greatest things about the CVT is – its makes your kart go faster, and increases the life of your motor. Imagine how many hours on your Rotax engine you’re saving if it is only revving to 11,500rpm? It is an engineering marvel.

So if your looking for some serious speed, and don’t want to have to rebuild your engine every 5 minutes the CVT is well worth a look!


Continuously Variable transmission explained