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-   -   F800GS - RXV Shiver'ed Fork Conversion (http://www.advrider.com/forums/showthread.php?t=603554)

Gangplank 07-25-2010 11:55 AM

F800GS - RXV Shiver'ed Fork Conversion
 
Hi,
So in reading this thread:
http://www.advrider.com/forums/showthread.php?t=524147

I decided to take on the fork conversion. Turns out -W- was thinking the same thing I was a while back except I had planned to use some KYB forks off a YZ250F. After the debacle of going to Aftershocks at TriValley Moto only to find out Phil and TriValley split ways the night before I showed up with my forks in hand, ugh.... I decided to go this route.

I am starting this thread because a few of us have been asking questions of -W- and this will give us our own thread to communicate in. I'm going to quote the important posts from the above thread here so we'll have the info in one easy to reference place.

The short version is this: You can easily convert the front forks on the BMW F800GS. I used a set of Marzocchi forks from an Aprilia RXV450.

Here is the order of things:
Find used forks with simialr diamater (marzocchi Shiver45 forks are the same as ours but a much upgraded version of their fork)
Take them apart
Take the bottom foot adjuster from the donor forks
Take it to a local machine shop along with the bottom part of each F800GS fork
The machine shop can machine the bottom of the stock forks to fit the donor bottom (compression) adjuster
Take the internals from the donor forks + the fork tubes from your stock forks + fork caps from the donor forks
Bring it to a local and good dirt bike or dualsport suspension shop (I used McCoy's Offroad in Carson City, NV)
They will put it together for you
Be sure the add a spacer to reduce the travel on the donor forks (info is below in this thread)
Put it back to gether
Put forks back on
Ride and smile a LOT!

Gangplank 07-25-2010 11:57 AM

Here is where -w- started + a few posts along the way....

Quote:

Originally Posted by -W-
I just bought new set of these to be fitted to my F800GS when I have time to do the conversion at some point in the future (probably next fall). We will see how it goes, but basically should be relative easy thing to do when using parts of these ones and some parts of original beemer ones: http://www.marzocchi.co.uk/moto/45legsend.html

Biggest problem is to get 30mm more travel to the rear suspension also to keep the suspension in balance..

Quote:

Originally Posted by mousitsas
Contact hyperpro. They do custom things. You need a shock with 10mm (or so) longer suspension stroke than stock.

Quote:

Originally Posted by -W-
Both forks have been taken to peaces and it looks quite promising. Aluminum part of F800GS´s lower legs has to be machined to fit compression valve/adjuster of Shivers, but otherwise quite straight forward.

At the moment I have also decided not to put Shivers to F800GS as they are, but instead of that swap all the inner parts from Shivers to F800GS fork and make them as 230mm Shivers with full compression & rebound adjustments (bike was getting a bit too high to me with 265mm Shivers).

Currently I am traveling, so it it will take some time to proceed with this project, but I have already ordered new linear Öhlins springs (55Nm instead of original 44Nm) which I will put to these "Shivered" F800GS forks.:wink:


Gangplank 07-25-2010 12:01 PM

Next....

Quote:

Originally Posted by -W-
Physical conversion done + first rides. Next things is to valve whole thing to mach the bike and use. But even at this moment... wow!:wings

http://i638.photobucket.com/albums/u...-R_Shiver2.jpg

http://i638.photobucket.com/albums/u...-R_Shiver3.jpg

http://i638.photobucket.com/albums/u...-R_Shiver1.jpg

Stroke is at the moment 250mm (but I have also parts for 230mm stroke) and therefore forks are so high at the triples. I will lower them when the matching longer stroke rear shock is ready.

Springs are Öhlins linear springs (5.5N/mm) and they have currently 14-15mm preload which is almost half the preload original forks have (they have too much preload and too soft springs for my taste). And that is propably the thing why this setup is actually more plush/responsive than the original ones, even if the Shiver inner parts have still factory "motocross" valving.

And under hard braking.. No more huge nose dive and unstableness - completely different feeling & trust to bike than with the original fork. Still needs to be valved (and fine tune the oil level) by professional guy, but even at this point it feels really good...:evil But you have to remember that I'm not expert in any way what comes to motorcycle forks & suspension things. I'm more used to set up downhill & mountain bike's suspension! ;) But I like it a lot and I quess that is good thing..? :D


And then the maching longer stroke rear shock..


Gangplank 07-25-2010 12:02 PM

Quote:

Originally Posted by -W-
No you wouldn't. All necessarely parts straight from Marzocchi would cost at least 4xmore than whole forks from ebay. Only the one cardridge unit without base valve and top cap is 310e and you can buy whole new forks from ebay less than that.

Ps. and Marzocchi's spare parts policity sucks big time - they don't sell any individual parts to forks (except seals, sliders & shims). For example if your pistonring is damaged you have to buy whole cartridge unit to have the pistonring!:jjen


I actually did a bit of research on this and it is possible to order directly from Marzocchi USA. They get the parts from Italy and it would cost a lot. Good thing is replacement parts are available.

Gangplank 07-25-2010 12:10 PM

I decided to do this conversion. Thanks -W-!!!!!!

The sought after forks are a pair of Marzocchi Shiver 45's. They are used on a few different dirt bikes including the Aprilia RXV 450(confirmed) & 550(maybe?), Husky WR250, and possibly GASGASS.

I found a set off an Aprilia RXV 450 that had the stiffer springs. The Aprilia has 3 spring options. Light, reg, stiff. Info is available out there on the interwebz on this. Anyway, I put up a post on a aprilia forum and had 3 set offered to me. One from Santa Cruz and two from Europe. Seems not too hard to find.

Quote:

Originally Posted by -W-
:lol3

Aprilia RXV, BMW G450X, Husqvarna, GasGas, & Beta have these Shiver 45 forks at least. Remember to buy model which has also compression adjustment at the lower leg (some husky's don't have it even if the forks are called "Shivers")

That Shiver Factory 45 which I used was offered as an Marzocchi's "aftermarket racing fork" to some KTM, Honda and Yamaha models. I think it is basically same fork than normal Shiver 45. It just has that black special coating at the lower legs, but you don't do anything with those lower legs anyway..

My original idea was to swap the whole Shiver fork as it is to F8GS. Reason why I didn't do it was the thing that F8GS has taller upper legs than Shiver 45 has. This basically means that tubes are more inside of others in F8GS than they would be in Shiver 45 if you would use them (=more stiffer). Also if you would reduce the travel of Shiver 45's to something like 230-250mm the over all height of the fork would be too low for F8GS.

I have my forks apart and at the machinist now. I will be posting up pics and info once I get the quoted posts moved over. Anyway, once I get the feet machined locally the revalve work will be done by Ed McCoy at McCoy's off road center in Carson City, NV. It is close to me and he is a well recommneded shop. He does a lot of pro dirt bike riders forks and seems to know his stuff. Also a Race Tech Cetner for the NV/CA so good source for parts, etc.

I had the same question as -W- above. Will ask Ed when I drop off all the parts. I am planning to reduce the travel on my "RXV Shiver'd" forks to the stock travel of 230mm. Once I talk to ed we'll see which upper tubes I choose to use. My guess is that I will stick with the stock BMW's since they are basically the same. Love to have the silver ones.... pics later.


Quote:

Originally Posted by -W-
But remember that you need to have your "Shivered" the forks revalved by some professional since the damping isn't enough for the much stiffer springs that you will also need (and maybe some of you want to have really "plush" suspension damping too) . But the good thing is that they can be completely revalved and after that they should be really nice..:evil

And I personally like the thing that after that you can also service and change the shims by your self as you like and that they are "conventional" cardridges without any gas pressure (=more durable and easier to service in my book).

I didn't take any pictures from fork internals when I did the modification, but I can take some when I am taking them apart for the revalving if needed.


Gangplank 07-25-2010 12:12 PM

Quote:

Originally Posted by -W-
Forks have been now revalved by professional guy and.... jeesus they are sweet!:evil :clap :wings

http://www.mphuolto.fi/images/dyno.gif
Shock dyno (not my fork at the picture like you see;).

Now you can blast through rock gardens with unbeleavable speed since front end tracks really well - doesn't bottom out or bounce from the rocks. Couldn't be more happier!:freaky Revalving made a huge different like was excpected - best euros ever used on a bike!

Currently I am running with 240mm stroke at the front (+10mm to normal) since I also took one spacer away from original rear shock (about +10mm more stroke there too - now 225mm). I will go back to 250mm stroke at the end when I have my new rear shock ready. I also swapped all the Shiver Factory 45 inner parts away and installed all the inner parts from Aprlia RXV's Shivers because one of the Factory 45's inner tubes was damaged (already from the factory production line) and it would have cost more than the whole Aprilia forks!:eek1

BUT the good thing with those RXV forks is that they have spring plates more lower than Factory 45's are having -> no need to cut the tube and relocate the spring plate like you have to do with the Factory 45's!:clap

So in the end if you end up doing this conversion with the right parts (like RXV forks) it is REALLY easy and straight forward process:

1. Machine basevalve housings to lower legs.
2. Machine spacer to the damper rod. If you use RXV forks you will need 40mm spacer to get stock 230mm travel, 30mm spacer to have 240mm travel etc.
3. Put all the Shiver inner parts to you stock forks. No need to modify anything if you don't want to change the placement of bottom out piston which stock F800GS forks doesn't even have. And of course you fork is already having new bushes and seals;).
4. Put new springs and cut the spacers to get decired sag etc. I would recommend to use linear spring if you really want to have good suspension. I have Öhlins 55kg springs, 14mm of preload and 100mm of oil level/air chamber height at the moment.
5. Take the forks to some suspension guru who knows what they are doing. This part is vital to get these forks work like they should since you have much stiffer springs that the Shiver inner parts are tuned from the factory. Also valving of the stock Shivers can be a bit hars sometimes.
6. Enjoy of you new suspension!:freaky

...and next thing for you will be rear suspension because now the front is "too good" compared to that..:lol3

.

Gangplank 07-25-2010 12:14 PM

So just to clarify there is no need to machine the top caps. They fit right in the BMW stock forks. Here is -W-'s answers to a few questions I had re: springs, etc.

Quote:

Originally Posted by -W-
No need to machine top caps if you use Shiver 45 based forks as transplant like RXV has. SXV has (as far as I know) Shiver 48 based forks and they won't fit since the top caps are also propably 3mm larger than 45's have.

Then what comes to springs, only linear springs which are available (at least I don't know any others) are Marzocchi's 0.5 springs, Öhlins 0.55 springs and Bitubos 0.6 springs.

I weight something like 90-93kg but naked, but you really shouldn't just copy-paste my settings since it is a bit individual thing how you want your suspension to work and what kind of behavious you like.

And what comes to other "similar weight bikes", KTM 990 Adventure uses 0.49 springs (215mm travel)) (S model has 0.48 and 245 travel) and Superenduro uses 0.59 (and has 255mm travel). I rode 990 and thought it had a bit too soft springs to my style (and it weight more than F8GS). Then on the other hand I don't use my beemer in a way that Superenduro was ment to be used -> didn't want to go even stiffer springs -> Öhlins 0.55 springs seemed to be nice starting point and the sag seems to be be quite nice with it (remeber that my setup is designed for 250mm travel).


Gangplank 07-25-2010 12:15 PM

Quote:

Originally Posted by -W-
http://i638.photobucket.com/albums/u.../Fork_comp.jpg
From top to bottom: Marzocchi Shiver Factory 45, Aprilia RXV Shiver 45, BMW F800GS.


http://i638.photobucket.com/albums/u...ning_units.jpg
From top to bottom: BMW F800GS (steel tube&steel rod), Aprilia RXV (all aluminium), Marzocchi Shiver 45 Factory (with shortened upper part of damping tube, all aluminium).


http://i638.photobucket.com/albums/u...R/Top_caps.jpg
From left to right: Marzocchi Shiver 45 Factory (with added bleed valve), Aprilia Shiver 45 (1:1 to Factory's), BMW F800GS.


http://i638.photobucket.com/albums/u.../Lower_leg.jpg
Machining for base valve at the bottom of the lower legs.


http://i638.photobucket.com/albums/u...Rod_spacer.jpg
Spacer for damper rod.


http://i638.photobucket.com/albums/u...rred_forks.jpg
Shiverred F800GS forks with 240mm stroke! :evil

.

Gangplank 07-25-2010 12:19 PM

Here is a post by GNP77. Not sure what forks he started with but hopefully he will post up what they were since the length needed some work on that set. Or he may have opted to buy a set of RXV forks in the end.

Quote:

Originally Posted by GNP77
Hey -W-, your overall lengths appear to be very close. The Shivers I bought are 250mm travel but the overall length is roughly 800mm and the stock F8 cartridges are roughly 890mm. I'm not sure how I'm going to tackle this issue. The wall thickness on the rod is fairly thick so I may get an extension (for lack of a better word) machined to thread onto the original dampening rod and just use a longer internal adjuster rod. Any thoughts?

Cory

http://gnp77.smugmug.com/Motorcycles...4_MFWrg-XL.jpg


johngil 07-25-2010 12:20 PM

Quote:

Originally Posted by Gangplank
Here is a post by GNP77. Not sure what forks he started with but hopefully he will post up what they were since the length needed some work on that set. Or he may have opted to buy a set of RXV forks in the end.

Looks like you were really excited w/ your work.:eek1

http://gnp77.smugmug.com/Motorcycles...4_MFWrg-XL.jpg

Thanks for taking your time w/ this.

Gangplank 07-25-2010 12:21 PM

More from him...
Quote:

Originally Posted by GNP77
I didn't have much luck finding used factory shivers but managed to snag a pair of 6month old (aftermarket upgrade) forks on ebay. I'm currently working through the swap, using -W-'s route as a map.


Gangplank 07-25-2010 12:34 PM

Ok, so in the end I am going to go this route. I found a set of RXV forks with the upgraded .50 springs in them for $225 shipped to me.

Here is what they looked like when I got them.
http://gangplank.smugmug.com/Other/S...58_vnFe5-M.jpg

Since I got the tripples I was thinking of putting the tripples on too but in the end I realized that however cool the bling factor might be... My goal is a simple and great fix.

My F800GS feet are at the machine shop now getting worked on. It will be between $75 and $150 depending on how long it takes for them to do the work. (1 or 2 hrs of work).

Next they will go to Ed McCoy at McCoy's off road center. Revalve at his shop is $140 and he is local so I can go back for some adjustments as needed. Other option was Superplush Suspension in SF. They definitely know their stuff too and work on a lot of big displacement desert racer's bikes.

Here are the BMW parts in a box ready to go next week.
http://gangplank.smugmug.com/Other/S...37_LLGwQ-M.jpg

Gangplank 07-25-2010 01:06 PM

I asked -W- a few questions about the spacer and shortening the length of the travel.

Quote:

Originally Posted by -W-
If you looks this picture:

http://i638.photobucket.com/albums/u...Rod_spacer.jpg

..you see the spacer at the bottom of the picture. Now just move that spacer 2cm to more up and there it is at its right place at the bottom of the damper rod next to valve stack! :wink:

If you make that spacer 40mm long you will probably have 230mm travel (if your transplant fork has same dimensions than I was having).

You could shorten the damper rod, but it would be more complicated project than just adding the spacer. And that spacer gives you alvays the possibility to tweak the fork travel later on..:evil

Br,
-KimmoW-

I beleive he also used a set of the RXV forks same as I am so he suggested a 40mm spacer if I wanted to keep the travel the same. From what I can find http://slorider.com/Aprilia/manuals/Specifications.pdf] online the travel of the RXV Marzzocchi Shiver forks is 298.5 mm (11.75 in). The stock BMW's are 230mm or 9 inches. So I'll be getting this info to my fork guy so he can work mine back to stock length and travel.

Camel ADV 07-25-2010 01:10 PM

I started with some random Shiver 45s off eBay. Not sure of the original source. The travel is 10" which is great but the over all length is 4" shorter so some dampening rod extension are in order. -W- is shortening his rods and building stopper-spacers and I'm having to lengthen...annoying! I am still working on getting a set of RXVs to do the conversion with and simply re-assemble the random Shivers and sell them on eBay again.

I'll got a set of HyperPro "Big Tank" front springs that are intended to be used with the Touratech 20liter tank. That is my plan in the near future so I opted to install them in the first place to save the work later. I'm 225 plus gear, plus cargo so I doubt the heavy springs will be an issue.

I got my lower fork legs back with the feet opened up on Friday. $105 from the machine shop which is about what I expected. I'm trying to track down a good suspension tuner to do a re-valve. As soon as I tell someone that it's a Shiver swap and not in a factory application no one wants to touch it...again, annoying.

http://gnp77.smugmug.com/Motorcycles...5_dXSwP-XL.jpg

Compression valve:
http://gnp77.smugmug.com/Motorcycles...6_UUY93-XL.jpg

Fits like a glove:
http://gnp77.smugmug.com/Motorcycles...2_69xNG-XL.jpg

A big thanks to -W- for his work with the Shiver swap. It makes it easier and cheaper for us followers to build things once someone else has done the trial and error!:freaky

Camel ADV 07-25-2010 01:14 PM

Quote:

Originally Posted by johngil
Looks like you were really excited w/ your work.:eek1

http://gnp77.smugmug.com/Motorcycles...4_MFWrg-XL.jpg

Thanks for taking your time w/ this.

Yeah, I enjoy working in garage a little too much! :wink:


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