F650 Dakar front end upgrade

[Benjah]

Well it was a long time in the making but my F650gs Dakar upgrade project is coming to a conclusion.

I've had quite a few people ask me about the various upgrades I've made to the bike, particularly the yamaha USD front end swap.

The new front end is from a Yamaha YZ450. The forks literally bolt right on. No hard stuff like welding is required. The springs in the forks were replaced with heavy duty springs.

And the result??

Night and day. The handling is SIGNIFICANTLY improved with the upgraded forks. This is clearly apparent both on and off-road.

I highly recommend the modification to any GS or GS Dakar owners. There's thread on ADV rider on how to do the conversion:

http://www.advrider.com/forums/showthread.php?t=399113

it's really long however so if anyone wants some advise/tips on how to go about doing this from someone local feel to ask. Or even PM me if you want to come and take a look.

The actual cost of the upgrade is really not that much because you can sell the BMW forks for more than the cost of the YZ forks.

Here's a picture of the bike:


Cheers
Benjah

[Eddieb]

Nice work, looking good.

[Benjah]

Cheers Eddy!

Just a thought..

It seems people have also mounted these forks on DR650's

http://www.thumpertalk.com/forum/arc.../t-908390.html

...

[Benjah]

Double post

[Box'a'bits]

Ha - I'm already in the process of doing this to my R100GS.

Couple of questions.
1. Did you reduce the travel (doesn't look like it).
2. Did you use the GS axle, wheel & brakes, or the YZ (looks like the YZ?). If the YZ how are you finding the brakes? What is the mastercylinder size on your bike?
3. What year forks (46's or 48's).
4. What did you respring to, & what have you done to the damping? Did you do that yourself or sent it out?

The only thing stopping me finishing now is the damned left fork seal & bushes have jammed in the fork leg.

[Benjah]

Ha - I'm already in the process of doing this to my R100GS.

Your going to love the result.

I'll answer these questions 1 by 1.

Couple of questions.
1. Did you reduce the travel (doesn't look like it).

No. I ride off road and hence want to enjoy the benefit of the forks full range of travel.


2. Did you use the GS axle, wheel & brakes, or the YZ (looks like the YZ?). Well spotted. I used the YZ wheel. YZ's come with excel wheels which are very high quality. I had the wheel trued and installed new bearings. I also used the YZ axel and brakes.

If the YZ how are you finding the brakes? I was concerned about the size of the stock rotor so I installled a larger 270mm wavey rotor on the yamaha wheel and new decent brake pads. I used the nissin Yamaha front caliper connected to the beamers stock brembo master cylinder via a sweet new steel braided line. The front brakes work really well. I can lock the front end up with two fingers.

Here's some pictures:




What is the mastercylinder size on your bike? Not sure but it's the stock f650gs brembo unit and it's fairly chunky.
3. What year forks (46's or 48's). 2001 46's
4. What did you respring, & what have you done to the damping? Did you do that yourself or sent it out?

I had the forks re-sprung with .48 springs from Racetech. The work was done by DAS in Christchurch. They specialize in offroad suspension and charged a very reasonable fee. I believe they addressed the valving as well.

Look forward to seeing your finished result.

[Box'a'bits]

Cool, thank for that.

I'm going with 48mm forks from a 2005YZ250F. I have shorted them to 225 travel from the 300mm travel available, to keep stockish geometry. The 48mms are a twin chamber design & the shortening was relatively straight forward (cut springs / put spacers in the damper to prevent fulll extension).

The springs that came with the forks were a 0.41kg/mm set - I am going to cut them, which will bring the spring rate up into the ball park (but will still likely be a bit soft). No revalving at present.

I'm also using the Yamaha wheel, axle, & caliper. The stock BMW ones weigh a tonne, and I don't use tubeless tyres, so no advantage sticking with them.

The caliper will be mated to the stock BMW 13mm mastercyclinder - the Yamaha one was 11mm, & didn't have a stop switch in it. Also it would have been a pain dealing to the switchgear.

I will need to do more work on the steering stops, & also re-mounting the trailtech vapor speedo / indicators

The rotor is an EBC supermoto 320mm.

How long you been back in Wellington - I thought you were Chch based now?

[Benjah]

yeah I need to work on the steering stops too. Need to fab up a bracket for the ignition as well.

I definitely agree with you about the springs possibly being too light. Especially given the amount of travel you've reduced it by.

A lot of the guys on the advrider thread were using .52 and .53 springs or progressive .48-.53 springs. An that's after shortening the forks and inch. Given that a R100gs weighs more than a f650gs, you may well find it bottoming more than you'd expect.

The full length forks are only an inch taller than the dakar forks so I just dropped them in the triple clamps by about half an inch and cranked up the rear pre lode.

Thats a nice chunky rotor you have got there. I would of liked to of gone that route but was to couldn't see any on trademe and was to lazy to look elsewhere.. These 270mm one do the job though.

I'm still in Christchurch. Better update my profile.

[Box'a'bits]

I won't be MX-ing it.

Got the left fork seal & bushing out this arvo. The bushings are well f****d. No wonder the seal leaked.

Stock R100GS springs are reputed to be 0.48kg/mm. Cutting the YZ250F springs takes it up to that at least. And the travel will be stock, so the main benefit should be in the damping, adjustability, & weight reduction.

The spacers were cut as 50mm & 25mm (total travel reduction 75mm), so I've an opportunity to play with the height at a later date. The main issue with this is that I don't want to:
1. Lose the stock geometry, given that the bike can push the front in gravel if the rear is down & the front raked out;
2. Increase the angle on the driveshaft - it already has 'potential reliability issues'.

I wanted bite in the brakes given I was going from a 4 pot Nissin conversion. I hated the lack of brakes using the stock 2 pot Brembo

Just switching tyres over on the rims - & I have noticed a flat spot in the rim I hadn't seen before......

Minor issues aside, coming together well now. Should be riding it next weekend...if not before.

Anyone want to buy a stock airhead GS front end?

[Eddieb]

Anyone want to buy a stock airhead GS front end?

I still reckon you should put it on the RS and make it a twin shocker G/S

[Benjah]

Got the left fork seal & bushing out this arvo. The bushings are well f****d. No wonder the seal leaked.

I can relate to that.

When I removed my rear linkage I found ALL three of the bearings with needles so badly corroded that the needles couldn't be separated. They had morphed into a single mega-needle.

I always wondered where the creaking noise was coming from

Bearings were replaced with well greased shiny new ones. Bike felt much better after that.

[Box'a'bits]

Thought I'd let you see the finished result, in case you didn't see it in that other site.. The seal savers are pushed up out of the way while I check travel.

[Benjah]

The forks look fantastic. That front rotor looks the business too. Did you order it from over seas? I can't find anyone in NZ who sells them.

How does it ride? Did you notice the weight loss?

I was thinking of putting on some seal savers as well but the suspension specialist warned me against it, advising that they can actually cause wear on the forks by collecting grit. He recommended simply wiping them down with silicon spray when they get dirty. There are a lot of contradicting opinions on the subject though.

[Box'a'bits]

The forks look fantastic. That front rotor looks the business too. Did you order it from over seas? I can't find anyone in NZ who sells them.

Got it from Procycle for USD199 +65 freight. It included the adaptor. The brakes are good - on par or slightly better than the 4 pot caliper on 280 mm rotor I gave up to go to this fork.

How does it ride? Did you notice the weight loss?

You bet. The bike feels more planted. The fork is definitely firmer than stock. I might need revaluing / lighter fork oil to get better minor road irregularity compliance (about in par with stock), but it takes big hits much better (speedhumps at speed). Haven't ridden dirt yet. Lost some steering lock.

I was thinking of putting on some seal savers as well but the suspension specialist warned me against it, advising that they can actually cause wear on the forks by collecting grit. He recommended simply wiping them down with silicon spray when they get dirty. There are a lot of contradicting opinions on the subject though.

For straight dirt bikes, maybe yes. The wear would be on the hard chrome. I'm trialling these, basically to see if they help with the seal wear. That said, I didn't have any issues with the KTM seals, so....

Here's the link across to the 48mm fork conversion thread for airheads, & also to the Gus build

[NordieBoy]

I was thinking of putting on some seal savers as well but the suspension specialist warned me against it, advising that they can actually cause wear on the forks by collecting grit. He recommended simply wiping them down with silicon spray when they get dirty. There are a lot of contradicting opinions on the subject though.

I'm running full length seal savers on the DR and have had no problems at all.
They can't collect grit, as no grit can get under them.

Shortie ones maybe...