Bike Reviews / Enduro

On Test: Two-Stroke Transfer – KTM release revolutionary TPI smoker

On Test: Two-Stroke Transfer – KTM release revolutionary TPI smoker

Seabas Romero

This is the moment that two-stroke fans around the world have been waiting for and a potential watershed for the future of the ring-ding stroker – KTM has unveiled the production version of its fuel-injection two-stroke engine with the all-new TPI or Transfer Port Injection EXC 250/300 models.

And it is the TPI that is revolutionary. There have been ‘efi’ two-stroke engines before but these were effectively an electronic carburettor, delivering fuel mix into the inlet port just like a carb. The KTM though features two injectors which squirt neat fuel into the cylinder transfer ports, into the airflow, which according to KTM gives optimum atomisation.

2018 KTM EXC TPI 250/300

Lubrication of the motor is taken care of by an electronic injection system which delivers carefully metered oil into the inlet port. Oil is carried in a separate tank with the pump incorporated in the tank.

The end result of years of research and development is manyfold. There’s a performance gain, which you will read about shortly. There is the benefit of reduced fuel consumption, due to perfectly metered fuelling. There are reduced emissions – so important these days – and guaranteed optimum ‘carburetion’ regardless of elevation or weather conditions, so no jetting considerations to worry about. Combustion smoke is reduced by some 50 per cent. Significantly this gets the two-stroke through the Euro4 emissions limit.

All of this technology is electronically powered, so a larger 196W generator, as fitted to the four-strokes, is utilised.

As KTM rightly says, this is a real game-changer in two-stroke technology and shows the Austrian firm’s continued commitment to the engine type which lends itself so well to off-road application.

Looking at the bike you would be hard-put to ‘spot the difference’ as the rest of the EXC mechanicals in this 2018 designated model remain pretty much as you know and love, with the strokers having been treated to a comprehensive re-design in 2017. You get the tough wide-ratio gearbox, diaphragm clutch, electric start and no-tools quick change air filter set-up.

The KTM trademark chrome moly steel chassis is fitted with the WP Xplor 48mm forks up front teamed with the Xplor PDS linkless rear shock with Brembo providing the stopping power. Most off-roaders are well versed with how a KTM handles and nothing has changed on this front.

There isn’t anything that anyone can teach KTM about designing an off-road racer and with its TPI innovation it hasn’t just moved the bar higher, it has set a whole new bar!

For sure other manufacturers will now have to implement some form of fuel injection into their two-strokes now – but it might not be quite as simple as copying the KTM as there will surely be patent and copyright issues.

That’s a whole other issue though, right now KTM is very much in the present and has implemented the most exciting change in two-stroke technology since the exhaust power valve – and a change with much, much, further reaching consequences and potential.

So, the KTM EXC TPI 250/300 two-strokes are here – all you want to know is what they are like to rip.


The venue chosen for the World Launch and first test of the 2018 models was the world famous Erzberg ‘Iron Giant’ and the vastly experienced TMX tester Martin Craven, a veteran of riding the Erzberg Rodeo on KTM strokers, is the perfect racer to test the ground-breaking TPI 250/300 Katooms.

Says Martin, Let’s go…to say I’m excited about the first test of 2017 is an understatement as not only am I testing one of the world’s finest and innovative enduro machines but I’m riding at the awesome stomping ground of what is known as ERZBERG.

I’ve been lucky enough to ride here before at the Erzberg Hare Scramble and proud to have also crossed the finish line a few times on the Iron Giant.

The KTM family has always prided itself on being one step ahead of the opposition and is equally proud of its motto “Ready to race”. And with the arrival of its unique 250/300 TPI EXC models, the 2018 model year is definitely no exception. Fuel injection two-strokes – let me at ‘em!

Going into the test I’d heard a couple of rumours hinting that the bikes lacked horse power and they didn’t pull from the bottom! I want to quash all those rumours right now by stating that the new TPI enduro KTM is a complete master-class in engineering and performance. Right from pulling away from the parc ferme its smooth and mellow response at the throttle was an absolute delight.

KTM pulled a blinder bringing the world’s press to such an iconic venue as Erzberg. It could so easily have backfired as everybody knows it’s the biggest and hardest playground in the world.

If this bike was going to fail, it was going to fail here. Mainly from the advantage of having ridden the event myself over the years on the same bike (but carburated of course) I know how hard the climbs are and I know there’s no second chance on them. Oh, did I mention that Jonny Walker (THREE times winner of the Erzberg rodeo) was the tour guide for the day. Were we in for a ride, how much fun can you take?

Going into the woods first on the 250 TPI, I instantly noticed how incredibly smooth the power was, the bike was still cold yet there was zero choking and very little smoke from he exhaust, the tickover was perfect and it picked-up and revved super clean throughout.

The bike itself is still the same clean, light, compact EXC of old (yes, I know it had a major revision last year!) with added fuel injection so riding-wise I already knew what was written on the tin.

What I wasn’t ready for though was its sheer incredible performance. First thing I noticed was the lack of wheelspin, the power delivery is so precise and smooth so it didn’t have that explosive punch you got with the previous models. What you get is nice, tractable power which coped beautifully with all the tree roots and slippery climbs in the woods.

It was so good that I found myself thinking, no way is this bike going to climb those ridiculous Erzberg hillclimbs that I just knew we were going to get to eventually. Throughout the morning I was swapping the 250 and the 300 with Jonny, so I was getting a good sense of both machines.

So, riding the 300 out of the woods we reached a genuine Erzberg section called Bathtub! It’s a hillclimb used in the Hare Scramble which, incidentally, stopped a quarter of the entry in 2016 – so it was a good test. Then, my God, when I opened up the throttle on the 300 it just shot up the hill like a bullet out of a gun.

How can a bike with so much bottom end smoothness have this much power at the top? After a few storming attempts at the Bathtub, which it levelled with ease, we moved onto the biggest hill in the event, aptly named the Three Kings. This is a huge, flat out in third gear monster of a climb which incidentally stopped Graham Jarvis in his tracks on his first attempt, forcing him to turn around and start again (trust me, you don’t want to be going down this either!).

I know that we weren’t approaching these hills in race mode and usually I admit that I’m pretty knackered at this point in the race but let me tell you this bike is unbelievable!

I nearly had to brake towards the top, the engine just kept going and going, the steeper it got the faster the 300 TPI went. I was then shell-shocked when, jumping on the 250 TPI, we got the same result.

Unbelievable performance from both bikes. I’ve never experienced power delivery like it where the bike actually gained speed the steeper it got. I really don’t think there’s a hill these two bikes wont conquer.

Just looking at the bikes you struggle to see the difference between the TPI system and the old carburettor models. And that’s a good thing because the basic characteristics of the KTMs are obviously very similar

With the revolutionary TPI  it certainly isn’t a case of KTM re-inventing the wheel…just improving it… massively.

250 or 300

There used to be quite a difference in power delivery between the two models but the TPI models both feel very equal in terms of power delivery, being so linear it’s difficult to say!

The 250 rides with a certain softer feel to it, only noticeable when on the very bottom of the pipe, it has a mellower feel.

Both 250/300 have a solid and clean, free running feel when on the throttle when climbing. What’s amazing is you can be riding at one mph in third gear, then snap the throttle open, there’s no hesitation or choking and then boom – you’re up the hill!

On the big climbs the only difference between the two was the 250 reached the top with ease while on the 300 I had to brake before I flew over the top!

In previous years the 250 has been my weapon of choice, partly based on how aggressive the 300 bottom-end power has been – especially last year’s bike which was just too snappy and not that easy to ride on the slower, loose stuff.

The new TPI machines are super predictable now and I honestly think the 300 is a master-class in riding excellence. It doesn’t kick you off-line unexpectedly and best of all there’s very little whisky throttle because with the fuel injection the power is so linear.

The 250 is exactly the same riding , just slightly less top-end lug.

Both are fabulous bikes to ride but, personally, I think the tides have turned and the 300 is now the stand-out choice for Clubmen, Expert and Pros alike!