Vortex OK DDS Engine Review

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With the recent announcement that Vortex will be the official engine supplier for this years MSA OK Championships, I headed to Italy to put one through it’s paces courtesy of Vortex.

The test location was the South Garda Circuit in Italy, located near Lake Garda and I was lucky enough to be in the hands of the Tony Kart Factory Team, something the 2016 British Champions in the OK classes will be able to experience at the CIK World Championships in Bahrain this year.

The Vortex DDS 125 OK is a single cylinder two stroke engine with a push-to-start system with decompression valve. And then perhaps one of the things most worked on with the new OK engine, the Cast iron CNC made cylinder and power valve.

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First impressions

Before I went out for my first session one of the other journalists said to me “take it very easy for a couple of laps, this thing is very fast and if you go too fast too quickly you will spin.”

Prior to that ‘advice’ I had absolutely no forms of nerves and now I was starting to think I may have underestimated this machine. I was given no real instructions on the start procedure and that is because there is absolutely none needed. The mechanics started pushing the kart and after two or three seconds I heard the engine fire into life and with what must have been ‘go!’ in Italian I put my foot down.

Quick note – do not nail the throttle when the engine starts as this may cause the engine to flood. Just slowly push on the accelerator and the engine will come into life.

As I left the pits for the first time I immediately opened the throttle and was thrown back in the seat. It immediately brought a huge smile on my face, like if you were on a roller coaster for the thrill seekers out there. This engine is fast! Very fast! As I came out of the final corner I again nailed the throttle and I could feel the wind pushing against my body! By the time I got to turn one I was hitting the brakes in what is a flat out corner.

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Power valve

Out of the corners the power valve comes in with immediate effect! In a Senior Max you know the power valve is there as it’ll kick in after a second or two. With the OK you forget you even have one as in the blink of an eye you’re up to the speed you approached the corner in!

Some people argue that the power valve is the downfall to the Vortex DDS but personally I think it is one of it’s best assets and that seems to be the same amongst some of the OTK drivers. The kick out of the corners is something completely different to Rotax or X30, it’s instant and instantly fast! The engine never felt to dip in it’s acceleration at any point either. Round Lonato it felt it was still pulling at the end of most straights which is unusual and just goes to show how fast they really are!

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General feel & Tips

It’s hard to fault the Vortex OK DDS in terms of the general feel. It’s powerful, fast and noisy. One thing I found was how key it was to be smooth on the throttle. When I drove an X30 I didn’t need to be so smooth on the throttle but with the OK feeding the throttle in is key, this became apparently clear at Lonato’s new double left hander, turn 4.

In the first couple of sessions I found myself exiting the corner almost sideways and this was because I was just dumping the throttle. Even if you think you have this beast of an engine under control you’ll quickly realise that you usually don’t! Be very smooth on acceleration and feed the throttle in at a ‘steady’ pace. I say steady but as we know everything happens so quickly in Karting!

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Another tip I’d say is try and keep the revs up in the slow corners. At the back section of Lonato for two sessions I found myself exiting corners very slowly and this was because I was slowing the kart down too much. Now of course the track had a part to play in this but try and keep the revs up as this will avoid you sliding on the exit and will get you out the slow corners a lot faster.

In fast corners the engine is very forgiving. I was at times coming through turn 1 and sliding but still going ridiculously fast! It’s almost like the thing didn’t want to slow down it was amazing!

The extra speed also is due to the fact that the OK is a lot lighter as they do not require a battery, loom or starter motor. This is straight away noticeable on track, through corners and down straights, you can immediately feel the difference. It’s just like running 100 meters with a ruck sack on and then without!

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I have two fears for this engine in it’s attempt to break into the UK market and the first one being is there space? X30 is providing grids of 60+ then we of course have the Rotax classes which are still popular in Junior formats and TKM is on the rise once again, so where does the OK fit into all of this? I think the prize for winning the British Championships, in a factory drive with OTK at the CIK World Championships, is something that will certainly get people entering! Also the option to hire engines for the series (arranged by Super One and MSA) is another good concept.

My second fear is if it suits all the tracks or not. At Lonato the engine was great but it’s so fast I wonder if it will be able to achieve it’s potential at the likes of Buckmore Park and Larkhall? I think at all the other tracks on the current Super One calendar it’ll be fine, so I hope Super One will take this into consideration.

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Technical – Vortex OK DDS

  • Single-cylinder 2 stroke engine
  • Displacement 124,96 cc
  • Reed valve intake in the crankcase
  • Liquid-cooled through external pump
  • Push-to-start system with decompression valve
  • Mixture-lubricated
  • Analogic ignition
  • Bore and stroke 54×54,29 mm
  • Cast iron CNC made cylinder and power valve
  • 5/5 transfer ducts intake
  • Oval exhaust and 2 boosters
  • Piston ring L type
  • Balance shaft
  • Radial bearing C4

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Super One and the MSA have stated the below figures for pricing and hire options to do this year’s championship:

  • Set retail price (complete with exhaust and carburettor): £1,745+VAT (Junior) and £1,895+VAT (Senior)
  • Option for those contesting all three rounds to hire an engine at a special cost of £350+VAT per meeting (Junior and Senior)
  • Alternative option to hire engines on a one-off basis for £500+VAT.

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Lonato Track Review

Lonato is a fantastic track and gives you all the challenges needed in a lap. You need guts to keep it flat through turn one and once your past there you’re into turn two which tricks you on the exit with the rumble strip rising a foot or two!

The new hairpin is great for overtaking and the double left hander is well, bumpy! Very bumpy! Just hold on, that was my approach.

Then we have the chicane and the back three sections which for me were the hardest part of the circuit, but five minutes with Karol Basz and Marco Ardigo and I was flying!

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To sum up I can certainly say the Vortex OK DDS is the best direct-drive engine I’ve driven just purely down to the sheer speed and acceleration it can produce! It never stops to bring a smile on your face or keep you on your toes! Whether it’ll break the UK market well only time will tell but I think there’ll be plenty of drivers seeking that OTK Factory drive at this years CIK World Championships in Bahrain and let’s not forget the amazing feeling in just driving the thing too! I think it’s an experience all karters should have at some point, whether you’ll race them or not.

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Written by Chris McCarthy


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