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-   -   Yamaha forks on a BMW F650GS Dakar (http://www.advrider.com/forums/showthread.php?t=399113)

skibum_1260 10-23-2008 07:43 PM

Yamaha forks on a BMW F650GS Dakar
 
Got alot of interest on this so ill try and post what i can remember about doing the upgrade. For starters heres a pick. The forks i used were off of a YZ426f, came with triple clamps, brake caliper and then picked up an excel wheel all for 250 bucks! Put in a heavier weight oil and then the heaviest springs i could find for the forks, new seals of course. The main two issues i remember having(did this last winter) were i had to machine the stock yamaha steering stem down about .010" for one of the bmw steering bearings, the other one fit like a glove! Also i had to trim the inside of the fairing so i could swing the forks without rubbing anything on the inside, and i also think i had to do somethin for the fork stops to work also. But let me know if you have any more questions and ill try and get some better picks once i wash my bike, its covered in a pile of mud right now! But i measured the weight difference of the two it was about 15lbs savings, the new ones were a bit longer then that dakar forks, but handles like a new bike now, and the front end feels so light and no more bottoming out!

johno 10-23-2008 11:16 PM

Skibum, if you use the Yamaha bearing kit, you dont have to machine the shaft. The BMW, and Yammy have the same size outer cup diam.
I used the Yam bearings on my GSPD conversion, and the GSPD has the same bearings as the 650GS/Dakar.

WayneC1 10-24-2008 03:17 AM

Interested in the actual difference in length and also the size of the disc rotor.

You have not mentioned the upper fork yoke & whether it is the Yamaha one.

How do you find the braking performance compared to the BMW disc & rotor

johno 10-24-2008 06:02 PM

You use the upper and lower Yamaha yokes.
Not sure on the 650, but I use the BMW wheel and brake on my GSPD.

michnus 10-25-2008 04:13 AM

Now this might warrant me to keep the Dakar. :thumb Tell me more about the way it performs, does it not make the front end to light? The KTM640 is very twitchy over rocky terrain, where the Dakar normally just plough through, yes, I know it's fronts are rubbish, but it does work there for some reason.
The only problem would be to mod the ABS ring and sensor on the ABS bikes.

Did you also fit different handlebars and did you had to do other mods to the switches and throttle?

2Advent 10-25-2008 10:41 AM

Hi, what I would like to know if you tried using BMW wheel set, and if it would fit, and why you went with the yammi wheel set?

BikePilot 10-25-2008 01:20 PM

The conversion certainly looks the business. :clap

If it were me I'd consider an oversized rotor and supermoto caliper for better braking. The brakes are suitable for a 240lbs bike off road, but for me they would be insufficent for road use on such a heavy bike.

Were you able to buy sufficiently stiff fork springs? The GS has got to weigh about 200lbs more than the YZF.

skibum_1260 10-25-2008 10:34 PM

Quote:

Originally Posted by BikePilot
The conversion certainly looks the business. :clap

If it were me I'd consider an oversized rotor and supermoto caliper for better braking. The brakes are suitable for a 240lbs bike off road, but for me they would be insufficent for road use on such a heavy bike.

Were you able to buy sufficiently stiff fork springs? The GS has got to weigh about 200lbs more than the YZF.

Breaking has not been an issue with the stock setup, lots of offroad and onroad miles ive never needed any more stopping power, that was one thing i was concerned with but it hasnt been an issue at all, and the springs yeah i seem to have them pretty close, dont feel to stiff and havent gotten it to bottom out once yet even after some descent jumps, you may have trouble if your a heavier rider but im only 175 so the heaviest ones i got worked well for me.

skibum_1260 10-25-2008 10:35 PM

Quote:

Originally Posted by 2Advent
Hi, what I would like to know if you tried using BMW wheel set, and if it would fit, and why you went with the yammi wheel set?

no idea if they would fit im sure you could but yamaha wheels are cheap especially excel wheels versus the cost of an excel for the 650 front end.

JDLuke 10-26-2008 03:12 AM

I commented on this conversion in another thread, and I'm glad to see a new one dedicated to the issue. I'm really interested in pursuing this, and will be haunting eBay for the parts I need.

One thing that adds just a little complication to my conversion is that my bike has ABS. At a bare minimum, I'd need to put together some kind of custom bracket for the sensor, which currently mounts right to a hole in the fork leg casting. In addition, I'll need to adapt the sensor ring to whatever wheel/brake I wind up with.... So I think I'd prefer that it remain stock if possible. Might need to talk to Woody about adapting that.

From casually browsing the listings, it looks like bikes from about '98 to '03 had forks roughly similar in diameter to my stock Showas, although upside down of course. That ought to be plenty strong I reckon. It looks like larger tubes came out in '04 or so. I'm wondering a bit about clearance issues if I went for the larger, and presumably stronger legs.

johno 10-26-2008 03:34 AM

Mine are off a 2003 YZ450. 46mm lowers. The bottom tripple is around 30mm wider than the standard 650 tripple, so may have clearance issues on the 650. ( mine on GSPD)

The other option for the front end is Honda XR400R forks. Not sure on the size, but I know the XR250R is the same size as the BMW, so dont need to change tripples.:D These are cartridge forks, so are modifiable.
Just another option that maybe cheaper again.
Check out FAQ at www.f650.com section on fork upgrades.

BikePilot 10-26-2008 06:13 AM

Quote:

Originally Posted by skibum_1260
Breaking has not been an issue with the stock setup, lots of offroad and onroad miles ive never needed any more stopping power, that was one thing i was concerned with but it hasnt been an issue at all, and the springs yeah i seem to have them pretty close, dont feel to stiff and havent gotten it to bottom out once yet even after some descent jumps, you may have trouble if your a heavier rider but im only 175 so the heaviest ones i got worked well for me.

Cool stuff. For the springs, check the sag. If they are too soft and you have too much sag you'll be riding in the much stiffer mid-stroke too often and more preload or stiffer springs may improve things. You should have around 80-95mm of race sag with those forks:)

dwayne 10-26-2008 11:44 AM

The KTM is "twichy" in the rough stuff because of the geometry, rather that the forks. This is a charachterisc common to many KTM to provide nimble handling in the tight stuff. Most KTM guys run a steering damper to get the best of both worlds.

I am planning a swap using 50mm WP extreme convensional (rather than inverted) forks. For my purposes the Dakar is a adventure bike that sometime goes dualsporting, rather than a dual sport that tries to go dirt biking. Conventionals seem to have better fork seal life, and the WP's are fully adjustable. I will use the stock BMW wheel and brake, I feel the dirt bike brakes with their thin thin rotors just won't handle 800+ lbs (trip loaded with me) just aren't going to last.

drivenbydiscovery 10-29-2008 10:12 AM

Quote:

Originally Posted by BikePilot
The conversion certainly looks the business. :clap

+1 !!! :D

definitely on my "to do" list (right after getting a new engine. :wink: )

El Cazador 11-05-2008 06:09 PM

Very interested in replacing my wrecked 07 front end this way. However could use some advice on what to do with the abs.:jose


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