Ep 11: KTM forks on a BMW F650

We’re back with our much-anticipated special project: fitting a set of KTM inverted or USD forks to Richard’s BMW F650 Dakar.

Now that we’ve got Richard’s “number two bike” back on the road, it’s time to get cracking on “number one” – the F650 Dakar that he rode to Singapore in 2003.

While no.2 (also an F650 Dakar) is Richard’s daily hack, no.1 is the sentimental favourite because of its history. A while back Richard decided to turn it into something special and has been progressively getting things overhauled, powdercoated, polished and blinged up with stainless steel bolts.

But the big-ticket item is a set of KTM inverted or upside-down (USD) forks – the factory-fitted variety made by WP Suspension. Whenever we’ve mentioned this on ADVRider or other forums there’s been a big response – so this episode, where we explain the conversion, should prove popular.

Richard started out with a set of 43mm forks he bought off eBay, and things were looking promising as it appeared a little machining on the steering stem would be the only major job to make it all mate up. Sadly, these particular forks proved unsuitable for our specific purposes because they were from a 640 Supermoto.

We give the full story in the video, but these forks could most certainly be used on an F650 depending on whether you were building a street motard or a dirt-oriented machine. Getting the steering post and bottom yoke machined to take BMW bearings is relatively straightforward.

In the end, Richard bit the bullet and got some 48mm forks from a KTM 950 Adventure like Pete’s. We have carefully planned how we will make these fit, and issues like the steering stem, ignition lock, brakes and various small modifications are well in hand.

Watch the video and you’ll get the picture. Then fire away with your comments and questions.

– Waz

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19 thoughts on “Ep 11: KTM forks on a BMW F650

  1. Hey Guys,

    Very interesting this is, especially being a Dakar owner too… I guess the main reason you are doing this project is for the whole unsprung balance reduction handling thing…? Just wondering why specifically you’ve chosen the KTM front end rather than say for instance the F800 GS front end – is there something about the KTM kit other than perhaps second hand availability and price that I am not aware of…?

    Looking forward to seeing the next part in the series… In fact looking forward to seeing the motorcycle sometime – will it be going to this year’s HUMM?

  2. Hey Noel,

    Thanks for your comments. At the time we started looking around for forks (which was some time ago now) the F800 was just coming to market and we didn’t know of any being broken. Conceptually there is nothing to stop someone using the F800 front end (45mm USD).

    We took our lead off what Touratech had done on the bikes prepared for the real Dakar rally. The Touratech conversion for the bike was based on 43mm WP forks.

    On the second hand market they seem primarily to come from Supermoto 620s and the 640 adventurers. But as you can see from the video the fittings for the brake calipers can make life challenging. At some point, KTM moved up to 48mm WP forks on the 640 adventurers and they came as standard on the 950s. Looking at the weight of the BMW versus the 640 adventurer and 950 adventurer (and bearing in mind we have the Touratech big tanks for this bike) we figured it was closer in weight to the 950, so those were the forks we went for.

    We know of another UK guy who has used similar forks off the KTM 950S which have even greater travel, but we understand he had some handling issues and needed to push the forks through the clamps a bit – not sure of the details.

    The main reason for doing this … kind of lost in the mists of time. It seemed a good idea at the time – we’ll see if it proves to be the case. We are also running at 18-inch rear and have a WP rear shock which we think will balance out the changes we are making.

    Yep we hope to be at the HUMM – Dakar included.

    Cheers,
    Richard.

  3. Hey Nigel,

    As well as what Richard’s mentioned, fitting and adjusting the top steering head bearing on an F650 is insanely complicated – on the KTM yokes it is simplicity itself (relatively speaking).

    As far as weight savings go: the BMW yokes alone weigh a ton!

  4. Good stuff as usual.

    I put KTM forks to my DR650 and ran into all the same issues as you. Wish I would have known about your project, then I could have saved you some grief.

    Not sure where you are at right now, but any more questions just ask. I have 6 different KTM forks and brake setups here so I humbly consider myself a (wanna) expert. Learned it all the hard way!”

    Cheers,
    Lukas

  5. Hi guys,

    Thanks for another episode! Got an F650 Dakar myself and was interested to see this episode. Question now: is there a REAL difference for “upside down” fork (not only on a f650, but in general). At times, the front on my f650 feels a bit wabbly… does an upside-down fork help?

    Keep it going, guys! Fantastic show!
    Bjorn

  6. Hi Bjorn

    We are shortly going to put up the next episode on the project. We are just awaiting some lower fork guards in order to deal with the front brake cable management and then the bike should be on the road. We are taking it to the Horions Unlimited Mountain Madness event in July and hopefully we will give it a good test nd report back on the effect of the upgrade. Will it make a difference to stability, off roading, handling etc….who knows but here’s hoping!!

    Richard

  7. Hi Guys,

    I have spoken to Rich in the past about the KTM Adv setup in the past.

    I have quick pointer. I took my bike to a little play area over the weekend. The bike was using the full travel on the jumps. Basicly I was bottoming out all the time. In fact I also blew a fork seal. Doing some research I have found that the stock spring rate of the ADV is pretty low. You will need to increase this. On ADVrider they are quoteing some numbers in the yamaha conversion thread you might want to have a look at.

    All the best!

    G

  8. @George/Komatias,

    That’s interesting. Picture is blurry but it looks to me like your forks could be from a single-cylinder Adventure, not a 950 like Rich’s conversion uses. Am I correct?

    So far we’d surmised that the 950 weight would make the forks pretty good for the F650 or even a little on the firm side – but balanced out by the wet weight of long-range tanks.

    Either way we’ll be interested to see how Richard’s bike performs and obviously he’ll be taking it slowly at first …

  9. As i recall George you are using the 950 Adventurer S forks which have even longer travel than the standard 950 Adv forks.

    So Waz, the forks are conparable.

    I briefly was chatting to Paul the mechanic at Bracken and his only comment was the spring rate might need adjustment.

    It is something we will have to investigate further once we have done some field tests!

  10. Hi Guys

    The forks I have are the Adventure S forks from a 2005 bike if I remember correctly. I had an issue with the handling initially but had not looked at my sags in detail. I got the geometry sorted out by pushing the forks up through the triple clamps by 35mm measured from the top of the fork to the top of the clamp. With the preload I tweeked the sags but I still get bottoming of the forks. From rough calculations for myself (around 105kg’s with gear) I feel that I need to go to a spring stiffness of around 5.6N/mm maybe even stiffer. Bear in mind that the bike the forks came from is designed for a 75Kg rider.

    What you could do to avoid buying new spring is to cut the stock ones and use spacers. This is debated to death on Orange crush over on Advrider. When I make measurements I will relay the info.

    To show the extent of the bottoming I made a video. The jump is not high but the forks went all the way down. Thicker oil will reduce the tendency to bottom but you really need the stiffness of the spring itself.

  11. Hello,

    I am Dimitris from Greece.

    Would you like to tell me about the forks and the steering column system?

    Are the forks 43mm steering column system and from the 950ktm ADV or from 950ktm ADV S?

    I am waiting for your news.

    Many regards,

    Dimitris

  12. Hi Dimitris,

    * The forks are from a regular 950 Adventure – not the S model.

    * The yokes are from the same bike as the forks, BUT …

    * The steering stem (sometimes called the steering post) is from a KTM Supermoto. It is a much more suitable length for the BMW steering head. We maybe could have used the Adventure steering stem and got it shortened and re-threaded – but we already had the Supermoto stem machined to take the BMW bearings when we were thinking of fitting Supermoto forks. So we had the Adventure stem pressed out and replaced with the Supermoto stem.

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  14. I want to ask if George aka Komatias is from Greece and if I will have taken his telephone number or his e-mail to have a discussion with him about wp front fork for BMW F650GS?

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  16. Hi guys and well done for your work!!I’m Antonis from Greece and i have an f650 funduro. I’m interested for a super motard conversion. What i want to know is if ktm super moto forks like these you have on your video are suitable for my bike. What are the required modifications that needed to fit on my bike?? Thanks a lot!!

  17. Hi Antonis, I have forwarded your question to the other guys to see if they can come up with some advice. I’ll start by saying though that the forks used on Richard’s bike were from a 950 Adventure, not a super moto. There were various reasons why Richard chose these forks for his particular application. He started with some other KTM forks but changed direction, I think it might have been to do with axles and the hub and wheel combination he wanted to use.

    In your case I can’t see why you would not be able to make super moto forks fit your bike, as long as you are prepared to have the centre post of the yokes modified to accept BMW bearings etc, make some sort of steering lock arrangement etc.

  18. Hi Antonis,

    Hmmm tough call… After the problems we had, I’d say you’d want to go for specific super motard forks to avoid any problems with brake caliper spacing etc.

    Probably forks from the 640 super motard would be best.

    Not sure how the steering stem etc would work on the Funduro though as it’s a different frame to Rich’s bike that you will see in our videos.

    Also need to be aware that with 17″ / 17″ combo the bike may be a bit twitchy when cornering…

    Sound like you may be wanting to just bolt something on… which is not the case. Whatever forks you use, there will be some modification required.

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