F650GS twin and TT fork springs

[gordo5]

I decided to go with some heavier springs because I'd scraped the bottom of the engine a few times, mostly in my awkward parking arrangement and once going a bit quick over some bad railway tracks. I added the bmw aluminum engine guard that I think either the 650GS or 800GS should have, but just proceeded to scape it up too. Generally, I found I was using all of the travel too easily. YMMV.

The springs are by Wirth and are distributed by TT as part number 040-0495 for about $180 CAN. They didn't appear to come with any instructions but what they did come with was all in German so I'm not too sure. The following posts are a few pics of the installation, and a comparison with the stockers.

The fork cap on these bikes is of the circlip type. Here I'm pushing the cap in to expose the circlip for removal. BTW, the front wheel is off the ground for all of this. This pic also gives you a good look at the TT handlebar risers. I have no affiliation, honest.

[gordo5]

Once the circlip is removed, the cap pops partway out and requires a bit of persuasion to coax out, mostly by manually compressing the forks. The second one is easier than the first, so long as the first one is still uncapped.

[gordo5]

The cap removed, bottom side up

[gordo5]

Pull the preload spacer and then just use a straightened out coat hanger with a little bend on the end to fish the stock spring out. This was a bit of a surprise, for me anyway. The stock preload spacer is huge, biggest I’ve ever seen but I think I’ve only seen them from four different bikes. In the pic the lower spring is the stock one with it’s preload spacer and the upper spring is the Wirth one, along with the preload spacer that came with it. The total length of the each, including their respective spacers was about the same, which was a relief as the one time I’d done this job in the past the replacement spring was a couple of inches longer and you just re-used the preload spacer. I almost hurt myself with that install, having to compress the spring to insert the cap . With this one, since it’s about the same length it was no more effort than changing fork oil. I inserted the springs with the tighter wound section up, since that was supposed to be done the last time I did a spring upgrade and I didn’t have anything better to go on. Getting the cap in isn’t simple because of the seals… I gave it a tap with a rubber hammer (actually a dead blow). Then just shove it in further to replace the circlip.

Stock spring and preload spacer, bottom. Wirth spring and spacer, top.


The Wirth springs are a heavier gauge and are stiffer than stock except for the tightly wound part. I just did this today and only have had about an hour’s test ride on them and they perform as expected. Sweetly. It’s a much better solution than just using heavier oil as it firms things up overall but still provides a nice plush ride. Not exactly the most expensive upgrade out there either.


Cheers, Gord

[Ed@Ford]

Gord: Thanks for the pictures. The mushy F650 springs were obvious when I sat on one in Canada back in April.

Your bar risers....home made, TT, or??

DUH! Can't read...TT..right in front of me!

Thanks, Ed

[blackie]

Great write up, now you got my bank account worried.....

[JRWooden]

I'm a little surprised to see that only a circle clip holds the cap on ... my old H*onda has screw on caps. On that bike I thought the springs were just a BIT too soft and found a pair of replacement caps that had schrader valves on them. I popped those on and put just a few PSI of air in each fork and was happy with the result....

That might not be a good alternative for the F650GS as without a real fancy replacement cap water could potentially run down into the fork assby perhaps?

Any thoughts on air-assist? Here's a sample picture of the threaded kind....




JIm

[gordo5]

Originally Posted by JRWooden

I'm a little surprised to see that only a circle clip holds the cap on ... my old H*onda has screw on caps. On that bike I thought the springs were just a BIT too soft and found a pair of replacement caps that had schrader valves on them. I popped those on and put just a few PSI of air in each fork and was happy with the result....

That might not be a good alternative for the F650GS as without a real fancy replacement cap water could potentially run down into the fork assby perhaps?

Any thoughts on air-assist? Here's a sample picture of the threaded kind....




JIm

Hey Jim. Ya, I hear you. I've always been amazed that the circlip type works, but it does. The threaded ones must be stronger but my 650GS single used the circlip type as well and I rode it off-road a lot more than I intend to ride this bike. Held up fine over whoops with heavier springs, so I'm not concerned about them.... Just amazed...

As for air, well, I wouldn't hold my breath waiting for someone to make one of those for this bike. The only advantage I see to it is the ability to change it on the fly. Otherwise, more oil or more air is more or less the same basic effect, I think.

Cheers, Gord

[JRWooden]

Originally Posted by gordo5

As for air, well, I wouldn't hold my breath waiting for someone to make one of those for this bike. The only advantage I see to it is the ability to change it on the fly. Otherwise, more oil or more air is more or less the same basic effect, I think.

Cheers, Gord

Yeah... I didn't know if it could be done or not....
It would be more easily "tuneable" and I don't know anything about fork design, but it seems like adding air would (could?) potentially make the fork more "springy" as the higher air pressure would work like a spring while adding oil would reduce the air space making the shock stiffer, but perhaps also affect the damping ... which adding air alone would not do???

I am talking outta my here... as I do not know for sure...
but I guess it's a moot point since nobody makes the circle-clip kind with valves on 'em, and I'm sure NOT gonna try it ;)

Jim

[blackie]

Don't think the air system would work on the 650's forks as it doesn't have the screw on fork caps. It's caps are just held in place with the circlips. Any air introduced into the forks via schrader valves would probably just blow the caps off......

[JRWooden]

Originally Posted by blackie

Don't think the air system would work on the 650's forks as it doesn't have the screw on fork caps. It's caps are just held in place with the circlips. Any air introduced into the forks via schrader valves would probably just blow the caps off......

Agreed, I'm not going there, that's for sure ... It is the first time I have seen one that is not threaded...

Jim