KTM 640 Adventure

Stretton anon

By and large my motorcycling activities have been relatively injury-free. However, towards the end of last year’s riding season the KTM 640 I use for AdventurerRide’s big bike off-road days reminded me big singles need treating with respect .
A tell-tale clicking from the starter solenoid informed me the KTM’s battery had become discharged and and the only option was to revert to the analogue starting procedure. Standing fully erect on the kickstarter I brought a hefty 90kg to bear with as much force as could be mustered. Somewhere close to the bottom of the swing the KTM gave a mighty cough and launched me in a reverse trajectory skywards to the garage roof breaking my ankle in the process. Painful? Oh yes…
Of course if I’d bothered to read the handbook I would have known not to open the throttle during the starting procedure. Although the 640 has a good old fashioned carb, it also has a TPS [throttle position sensor] which I suspect threw the ignition to full advance creating a spark at the wrong time. I don’t think I’ve been hit so violently since the days I was taught by Catholic clergymen.
Some months on and still limping it’s time to reflect on the 640 Adventure and give a few riding impressions. I bear the bike no malice, but the fact a modern bike can deliver such a debilitating wallop to its unsuspecting owner underlines the KTM has no frills. No electronic trickery to minimise the possibility of kickback, no clever little cams which lift a valve to ease the starting procedure as found on some Japanese bikes . Nope , the 640 Adventure is a rugged , take-no-prisoners bruiser which the Austrian factory have kept down to a commendable 150kg.

KTM map

A GPS isn’t OE on the 640 Adventure but no matter, the Ghobi panniers are double skinned and can carry water/petrol/wine in the void between the two skins. The two screws at the base of the pannier are to fit an external tap. Now I ask you, would you rather have GPS or the ability to carry two two litres of Rioja with you on your adventure?

The low weight comes with a corresponding lack of refinement. At first acquaintance the 640’s single cylinder engine feels crude, specially when compared to something like a Yamaha 660. Its balancer shaft doesn’t eliminate vibes quite as well as the equivalent Yamaha or BMW single and the rider is always aware just one cylinder is doing all the work. A Jaguar car engineer once told me you can’t have refinement without weight and so it is with the KTM, it’s 30kg lighter than the equivalent Yamaha Tenere and there is consequently less mass to dissipate vibes. Compared to the Yamaha’s counterbalanced smoothness the raw -boned KTM feels visceral and uncompromising.

The flipside to the KTM’s diamond-in-the-rough demeanour is its off-road capability which is outstanding for a bike of its size, a true adventure bike in fact. The 640 will launch you down fire-roads floating imperiously over ruts and bumps which would have lesser bikes tied in knots. It will also plonk through deep mud and scabble up rocky inclines finding grip where you’d swear there wasn’t any. It’s this pedigree which helps generate the almost fanatical devotion of KTM’s partisan fanbase.
One of the quirks of the Adventure’s LC4 motor is the way it gets noticeably smoother when thoroughly warm. By thoroughly I mean after about 100 miles. A pal of mine restores vintage aero engines and knows a thing or two about motors and what makes them tick . Back in the day he bought a new LC4 Adventure and mentioned this characteristic of the LC4 engine, explaining that some engines behaved this way. It’s the kind of ‘character’ the Japanese endeavour to engineer out of their bikes. I’d completely forgotten about it until I went for a long ride on mine and after a couple of hours the whole plot settled down and smoothed out. At this point the 640 feels as if could thrum along all day eating the miles, which is something the Adventure excels at . It’s never going to be as smooth as the Yamaha or indeed the BMW 650 which has an engine of similar pedigree but it’s on the right side of acceptable. Of course it might just seem smoother after a couple of hours because your arse has gone to sleep.

big trail bike

Somewhere in the Welsh borders. On these kinds of trails in this type of country the 640 has a lot going for it.

On short gearing [standard gearing is too tall for serious off road use] the Adventure will buzz along happily all day at 60 to 70mph with 80 plus being available for short bursts of overtaking. Although the KTM is happy to rev, it’s a brave man who ventures anywhere near the 8500 rpm redline, 4000 to 6000rpm is the sweet spot and anything above this is unnecessary and can feel harsh.
So, having established the 640 Adventure is an agreeable, if not particularly quick road bike what’s it like off the tarmac? Bear in mind I’m not a fan of big bikes for serious trail riding, spoilt as I am by the 90kg Pamperas on the AdventureRide fleet. Therefore I approached the KTM with a degree of caution before doing anything serious off-road. On standard road gearing the 640 is unhappy in second gear on technical trails, I’ve rectified this by fitting a 15t front sprocket. Caution should be exercised on technical descents because the “stall speed” is relatively high and if you’re going slowly on slippery surfaces the engine’s high compression can lock the rear wheel and stall the engine.  The answer is to acquaint yourself with the arcane art of deploying the decompresser to prevent stalling. It’s an acquired knack needing a delicate touch but once mastered is a useful technique to know and might help avoid an embarrassing low speed spill.


Pressed into service during a recent photo shoot for Bike magazine. The 640 was a used as a mule carrying photographer Chippy Woods tripods, lenses and cameras.

During my six month tenure with the KTM I’ve done one or two minor maintenance tasks such as wheel bearings and starter clutch and have to say the bike is , on the whole, a joy to work on. Well engineered, robustly made and sensibly laid out, the KTM is a quality product. The paintwork in particular is stunning, it looks like standard KTM orange from a distance but in fact has a subtle metallic flip flop effect which looks fantastic in sunlight. However, like most bikes, the 640 ain’t perfect and scores low in certain areas. Particularly annoying is the seat retaining bolt. KTM’s designers have seen fit to retain the seat by a single hex-headed 6mm bolt located in the centre of the rear wheel well facing downwards to the tyre , perfectly situated to get coated in mud and road crud off the rear wheel every time you ride the bike. The battery lives under the seat and it’s feasible you might need to access it when out on the trail and finding the bolt can be difficult. I’ve slotted the head on my seat bolt with a hacksaw and Araldited half a penny washer to it so a] so I can find it and b] so I don’t need to use a spanner to undo it.
Other gripes include the fiddly oil change and filling procedure. Google it if you’re curious. It involves [amongst other things] bleeding air out of the frame via a hard to access bleed screw in the headstock. No big deal but not exactly user friendly or intuitive.
I would also criticise the left hand kickstart [OK it’s got a leccy starter so perhaps I’m being picky] the overly fierce front brakes – great on the road but a liability off it – and finally ,and this is a big one, a disappointing lack of flywheel mass. KTM are not the only manufacturer who are guilty of this. Yamaha, BMW , Suzuki and Honda all make big singles which are lacking in the trouser department when it comes to flywheels. The result is an engine which needs knocking down a gear on long ascents and judders when asked to cope with large throttle openings at low revs. On tight nadgery trails this is exacerbated by the large jump between 2nd and 3rd gears. A decent flywheel would solve all this.
The problem is, on all these bikes, the space normally occupied by a flywheel is now taken up by an electric starter sprag clutch mechanism. I suppose it’s the price of progress and instead of firing every lampost, modern big singles now thrive on revs and make their torque higher up the register. I’m afraid it’s the modern way. The sprag clutch  is notoriously fragile and mine needed replacing almost as soon as I got the bike. Starter clutch life can be prolonged by using the decompresser briefly whilst spinning the engine up on the starter motor. Pop the decompresser off and the engine usually fires instantly.
In summary I’m extremely happy with the 640 Adventure, it’s a true dual purpose bike in that it’s capable of being driven very long distances on the road, up to 300 miles with its 28 litre tank, and still make a decent fist of tackling quite technical trails when you get to your trail riding destination. Most important is that it’s actually fun to ride, unlike some of the 250kg big traillies which have to be treated with a great deal of respect on loose surfaces. Of course the larger capacity bikes will cover big miles cosseting the rider in a way the 640 Adventure could never hope to match but if you’re looking for a bike which is genuinely enjoyable to ride on or off the road you could do a lot worse than look out for a used Adventure.

Pye corner

And some final food for thought. These original 640 Adventures are starting to be seen as classics and hold their value very well. You can’t beat a bit of depreciation-free fun.

6 thoughts on “KTM 640 Adventure

  1. A great read and very informative. It looks like you need to know quite a lot about mechanicals if you are to own this type of bike, probably a bit more knowledge than I have.

    • Hi Steve,
      Many thanks for your kind comments. A small amount of mechanical knowledge is handy for any type of bike but I don’t think adventure bikes, or indeed KTMs require any more knowledge to run and ride than say a Honda road bike. KTMs are perhaps a bit more focused but they are well made and in my experience quite user friendly from a maintenance point of view. My own bike had done over 30,000 miles when I bought it and save for the starter clutch hasn’t required anything out of the ordinary. If I’d had a KTM specialist shop do the starter clutch I doubt if the cost would have exceeded £120 so it’s not too traumatic.Please don’t let my comments deter you from buying an adventure bike, they’re great fun and so long as you stick to something with a good service history you shouldn’t go far wrong. There aren’t many bad bikes nowadays, especially in the adventure bike sector which tends to have well-informed, discerning customers and as a consequence manufacturers seem to put a lot of effort into creating decent bikes.
      Ride safe, Bob

  2. Good write up. I have the 640 adv and have gone from a gsa to it, purely because it took me far too long (years) to realise you don’t need a huge 250kg lump to travel, but that said I wouldn’t like to go much under 600 cc for a 5k+ mile trip. I travelled extensively on the gsa and wouldn’t hesitate to use the ktm for future long distance trips I have planned. Your right about the mechanical side of things I’m a great believer in learn your bike before you go! The 640 is perfect for my needs. Very clever how the big manufacturers have marketed 1000cc + adv bikes being the only tool for the job when in reality the 640 sums up a perfect travel bike. ………helped along with my trusty air hawk under my backside!!

    • Hi Mal , I once rode a 640 with an air hawk and it was a revelation, ideal for covering big miles. My 640 continues to grow on me and the more I ride it, the more I appreciate it. I’m not sure there’s anything else on the market quite like it…

  3. Hi, much appreciate the tips provided! I’ve recently acquired my own 640A and getting to know the ins and outs.
    Could you maybe elaborate a bit more on this procedure: “Starter clutch life can be prolonged by using the decompresser briefly whilst spinning the engine up on the starter motor. Pop the decompresser off and the engine usually fires instantly.”

    Thanks again 😀

    • Hi Geno, Starter clutches are a high stress item on modern big singles and are put under tremendous strain during the starting procedure. In extreme cases, microscopic pieces of the hardened outer shell can flake off the rollers and find their way into the oil, please note this is not a problem specific to KTMs, it’s just a general observation about starter clutches. Fortunately the 640 has a de-compressor and this means that if you hold it in briefly when you press the starter, the starter clutch has a much easier time because it’s not fighting to overcome the engine ‘s compression. The engine will spin up very rapidly and if you then release the decompressor the engine should fire instantly. The decompressor is also really handy on slippery descents but I think I’ve covered that in the article. If you’ve never used a decompressor whilst riding before, try riding along a quiet road at about 30mph and deploy the compressor, the bike will slow and you will hear a twittering sound as gases escape from the decompressor, release the decompressor and the bike will smoothly fire up again and everything is back to normal. Once you get used to it it becames a very handy tool for riding off road. Of course its primary job is to allow the rider to easily turn the engine over on the kickstarter until TDC is found but it’s worth knowing a few tips as to what else they do. Ride safe, Bob

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