Yamaha forks on a BMW F650GS Dakar

I have begun the transformation.
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I purchased a set of 03 YZ forks (46mm) and will fit the BMW OEM wheel and brake. I prefer to use the larger thicker 300mm disc rather than the Yamaha 250mm-stock rotor. Oversize 270mm off-road and supermotards kits get expensive pretty quick.
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Confirmation for those contemplating such a modification on the bearing swap:
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The Yamaha bottom bearing has a 30mm bore and uses a larger cup OD and is a bit taller than the 28mm on the BMW. It does however fit into the smaller OEM cup quite well. I used the stock Yamaha seal and bearing with the BMW cup. If you cut the rubber lip off the bearing seal it fits nicely into the recess left to create a good seal. Grease will complete the seal very close to as good as the stock BMW but not as good as the Yamaha OEM set up.
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The top bearing is the same and I used the Yamaha top seal with a little bending to reduce the gap and greased it up well.
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The fender mounts under the front triple within about 5mm if you cut off the number plate tabs and drill new holes. I also made a strap to reinforce the attachment of the front of the fender. The front mounting holes are very close to the front of the fender and not as wide as the OEM holes. It seems to work well so far in mock ups.
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So now my challenges are
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<!--[if !supportLists]-->3)<!--[endif]-->Hanger for BMW brake
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I have some minimal machining capabilities at the house so I will start on those challenges this weekend.
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If anyone has ideas on the key and lock would love to hear it…

If you completed this project and have additional details or ideas on any part of the process please share them.
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Thanks,

Radman

JD any pictures of your modification would be a huge help. I am still contemplating trying this. I have the 03 yammy fork and would like to use the bmw front wheel if possible. i don't have the ability or equipment to make custom parts.
if you are making a custom key mount and want to make another to sell let me know. there is a small picture of touratech's solution to the problem on their web site under wp suspension kit- and then kit photo- if that helps at all.
Does anyone know if I do use the yammy wheel and caliper will it work with my existing touratech ss brake line?
thanks
matt

skibum any pics of your steering damper setup?
thanks

Dude,

You are right to think that the 250mm rotor is under sized.

What I am really gobsmacked by is your mix and match of the steering head bearings. You cant interchange races and bearing cages just like that. It is dangerous. If the bottom of the axle is 30mm then get someone to turn it down to the 28mm required. Dont mess about with these things, its you life. Please do not be offended I am just trying to stress the facts.
If the steering axle is hollow then maybe that is a bit of a problem if it is aluminium. If steel then just turn it down.

You will have to turn the spacers and get a different front brake caliper. The brembo one is abit dated and you will have difficulty finding hangers for it.

The steering/ignition lock is a bit of a problem. Dont know what the yama clamps look like but avoid drilling holes in them like the plague if they look cast.

Just so you know I am not bulshitting you on the above points, I have spent 4 year(ever since I got my dakar) trying to find a quick way to add usd forks to it and I have done it.

Komatias,
Thank you for your comments. I understand your concerns but I believe they may be somewhat overstated. What you say is applicable if the bearings were used in a high-speed application like a wheel bearing etc.

In a no speed - low load (relatively speaking) as long as the surfaces of the bearings and the cup meet as designed you will get satisfactory performance from the bearing. The 30mm bearing rides less than 1mm higher in the cup of the 28mm bearing and is within the machined wear surface of the bearing cup and still deep inside the steering stem. I believe it will work safely in this application.

Failures in steering head bearings occur over time and I have never heard of a sudden catastrophic bearing failure. They are usually attributed to lack of lubrication and infiltration of dirt and water allowing the bearing to beat themselves to death. It is witnessed by sticky or notchey steering and that is when it gets un-fun or dangerous. Letting that go is really bad.

FWIW, I am an Industrial Engineer by education, worked in the power-transmission and industrial automation fields for too many years to talk about. And I too have been doing this type of work...for about 40 years. It is not ideal because you have to buy 2 bearings to make it work but it is easier than pressing out and turning down the stem.

Your installation looks great. Thanks for sharing the album.

Are you using a KTM forks, wheel and aftermarket oversize off-road brake kit? If so, what manufacturer did you go with and how well does it work for you?

Thanks,
Radman

JD,
I to am an engineer but in new product development in the oil industry. My concern was that the rollers would be proud of the machined wear surface thus causing higher contact pressure. Also the tips of the rollers if not sat properly would wear a ring in the cup.

Maybe I did over state thing a little. As you say catastrophic failure is not common and the main cause of failure of SHB's is mud, dirt and water ingress. However, the failure effect can be catastrophic. (I had a husaberg previously and the lower bearing siezed just enough on one roller to make it interesting). If you look at a worn SHB, you will see that the wear mark on the collar ring is periodic recessess where each roller rubs. As you have far less full lock turns than little adjustments, the recesses are of varying depth and this is the dangrous bit. Any looseness on the bearings due to wear or "bedding in" and you are in for a shaky ride.

My set up is from a KTM adventure S 950. I got the forks, axle and clamps, then a front wheel from a KTM SX, the steering axle from an SX, a generic brake caliper from Husabergs/KTM's and a Braking supermoto 320mm Rotor and Talon caliper bracket.

Pressed out the original steering axle and replaced with that of the SX due to length. Had to turn it down by about 1mm to accept the BMW bearings as KTM uses Imperial bearings that have a steeper taper. Bought a set of 950 wheel spacers and turned the left one down to fit the wheel.

I also had to mod the ignition lock slightly to fit on the KTM clamps. Bear in mind that if you raise the front up a bit, you will be putting more weight on the back of the bike. I had to drop the forks about 2" in the clamps to get the weight distribution just right. Next step is a 18" rear rim.

If you need any more info don't be afraid to ask.

Nice set up what did you do for the rear?

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The rollers are within the race but just barely. I think it's going to work out on this swap. But as you say, it is generally NOT recommended to swap bearing and races. Especially wheel bearings.

Radman

SHB and triple clamps:
The first challenge was to get the triples installed and functional. As Komatias noted, it is important that the bearing is not "proud" of the race and a &#8220;mix and match&#8221; approach to bearings and races is not generally recommended. In this situation it fits and its close...but close enough for this application IMHO. A KTM 525 bearing cap (left over from the 07 Dakar bike) fit nicely on the top and protected the bearings well...perhaps better than stock when combined with lots of grease worked in and around the sealing areas to keep the bad stuff out. Be sure you pack the bearings well&#8230;you can refer to &#8220;Garage Night&#8221; YouTube&#8217;s for more on that.


It should also be noted that the Yamaha triples have a 25mm offset vs the BMW 23mm. The BMW axle mount make up for this with a larger offset as compared to the Yamaha forks but in the end I will end up with 3mm more trail that the BMW OEM setup. has anybody else worked this calculation and has experienced a difference in handeling either good or bad, I would like to know. Again, this could easily corrected with after market axle or tripples.

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The OEM fender was retained. This required that the bottom number plate taps be removed (cut off) from Yamaha triple clamp to allow the sub fender to go back far enough to align the bodywork. The fender was re drilled to mate to the clamp using some large washers. As it stands now, it&#8217;s about 10 mm forward of the OEM position relative to the steering stem. It looks good to me.

A bit of metal, about 5mm was trimmed from the sub frame (stamping, not tubing) that supports the front fairing and instruments. Just the corner of the stamping touched the forks when turned.
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I think you get a bit more lock with the new stops on the Yamaha bottom clamp. I trimmed the hand guard mounting brackets down to make them clear the instruments at full lock as well.

Steering lock and key:
I decided not to maintain the lock and key system on the Yamaha top clamp for now. I never use the fork lock and don&#8217;t have keys on the rest of the dirt bikes and haven&#8217;t had issues yet. Keeping it would require significant machining so I didn&#8217;t think it would be worth it based on how I used the bike. This may be the biggest drawback to the Yamaha set-up unless you&#8217;re using aftermarket top triple-clamps that have a good flat-machined surface to clamp a sub assembly too securely. But you still have to make the subassembly to mount the OEM mechanism.
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I went with MIL Spec 3 position toggle attached to a simple bracket that screws to the top clamp number plate 6mm threaded attach point. I extended the bracket past the attach point and kept it firmly against the clamp so it couldn&#8217;t rotate and through bolted the toggle switch. I may go the after market top clamp and integrate the lock at another time. Let me know if anyone needs the wiring diagram for the toggle mod.
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Front wheel and brake:
The question seems to be Yamaha + aftermarket bolt-on approach for more $$ vs. machining special parts for less money with the OEM wheel and brake but a great deal more time involved.
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Fork set-up:
I have been in contact with Cannon Race Craft and they will be shortening the forks by 1&#8221; and I will run them deeper into the clamps for the final ride height set up. I have the room with the bar risers. In the end they will be 1&#8221; longer than OEM Dakar forks. And depending on the 17&#8221; vs 18&#8221; rear wheel and sag measurements I may need the extra length. Cannon will also be re-valving the forks, new seals and wipers and making custom progressive springs set-up just for this application. They will be up around .80 but I don&#8217;t have the numbers yet and I won&#8217;t send out the forks until I get the front wheel/brake fitment resolved.
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Rear suspension:
I will also send the stock shock out to Cannon for rework and possible a new spring. I want to maintain the remote preload adjuster.
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Rear Wheel:
I believe that I will get an 18&#8221; laced to the OEM hub at the same time I do the shock to complete the transformation.
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I am off to check the valves while it&#8217;s apart today but I will be back on the front wheel and brake conundrum later this weekend.
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Hope this helps some of you that are contemplating such a change. Fire away with questions. I will try to get some pictures later as well.
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Radman

This project is going pretty well so far. I have the forks mounted and the axle modified to accept the BMW OEM wheel and rotor. I am working on machining a new hanger to utilize the BMW OEM caliper and it looks like I may go to a local machine shop to get this done.

Here is the logic behind using the OEM caliper. Most of the off-road kits for the Yamaha are 270mm and 3mm thick. SM type are 320MM but still 3mm thick. I think that may be a bit fragile for the application on a 400lb bike. The costs are running between $250 to $300 using the Yamaha OEM caliper. None of the Yamaha aftermarket stuff is as tuff as the 300mm X 4.5mm OEM an the matching caliper. It is the difference between designs for a 200lb vs 400lb bike.

If I were to develop axel, spacers and hanger models to have them manufactured in a quantity of 5 or so, it would be more affordable for all parties involved. The more we make the cheaper it gets. Otherwise, I do a one-off design and manually machine the parts.
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This works for me but its very labor intensive to manufacture a second one and it cost the same each time. I won't be doing this again anytime soon.

Here is the cost of my project so far:
Forks and triple $ 150
Toggle switch $ 30
Springs/re-valve $ 400
axle $ n/c
Hanger ????

Let me know if you’re interested, (everything shared at cost) and I will look into the cost issues later this week.

Radman, I am looking for parts right now for this mod. Are you using the yxf426 or yz450 forks?

I would be interested in sharing setup and machining costs with you as long as we are using the same set up.

Not...,
I am using 03 46mm YZ forks. From what I understand, wheels, axle and brakes are the same up to 07. The fork diameter changed around 04 to 48mm so the triple clamps are different.

All that to say the axle and the brake hangers would be the same.

If your using the 46mm forks, we can even try to get a better price on the springs since they too are one off specials.

Radman

I'm pretty sure that I just lined up a set of 03-05 YZ 450F forks. IF I don't get these, I'll definitely have a set in the next week or so.

So no one makes a set of springs for these forks that would work for a Dakar? Mine is currently at about 340lbs dry. Needless to say it stripped. No ABS, custom carbon fiber fairing and double light assembly (no instruments or metal support frame), custom 14oz tail fairing (no luggage rack and metal support brackets), rear sets have been shaved, battery lowered into ABS rack for lower CG. Stock exhaust has been replaced by 6lb Supertrapp slip-on (no connector pipe) All unneeded plastic has been removed.

If no one offers stiffer off the shelf springs then I would be interested in springs and the brake hanger bracket.

JD- I have a fork sitting waiting for this. I even bought a Yamie brake system, but do not what to use it after looking at it and the smallish rotor. I would love to be in on this- please count me in! Let me know what ya need from me.

Cheers-
Matto

I too have the 46mm '03 forks so would be interested in the springs depending on price- definitely in for the spacer, bracket, spindle.

Thanks!

I too have been staring at my 03 46mm forks wondering what to do about the front wheel/brake setup. I would be very interested in springs, axle and spacers, and hanger.
thanks

Me too, this conversion kit idea sounds good. My fork setup is same as below.

To all interested parties,

I have made progress on the drawings this week and will finish them up this weekend.

I expect to have something for us to discuss by the end of the week next week.

Thanks for the interest in the project and I will do my best to make it a win for us all.

Radman

Big progress this weekend. My buddy from IN has been a big help...not to mention we are having a blast.

I need some help from someone with a Dakar. Please grab an inside caliper or other measuring device of your choice and provide a measurement from the inside of the fork leg to the top most end of the rim on both sides and tell me what the differences are..if any.


I have butchered my OEM axle to mock up the front end for other measuring so I can't clamp the wheel into the forks tightly to confirm this dimension. This is the final cross check to be sure we have it ready to go.

We have a 3D model built and will be ready to start thinking about a prototype later this week.

Now I will wait to hear from one of the interested parties on that dimension and try post some pictures.

Left side 41mm Right side 39.4mm