My new JH600

[Pfaelzer]

Hi,

since some of you are considering to buy a Wilbers rear suspension system, I have edited the related post with some critical information. Especially, if you are going to get it built in by a local work-shop, this might be important to consider.

Please check this post:
REAR SUSPENSION MODIFICATION - edited 04-23-2010


I am working on details about the front spring conversion (change to progressive springs) and will call Wilbers in Germany during the next days about it. I will also tell them to take a look at these treads so that they can come up with an easier to assemble solution.

Greetings,
AW.

[bikerdoc]

Hi bikerdoc,

once it comes to the point, it really doesn't matter, which bike you ride. There are people going on all kinds or 2-wheelers around the world. From little 50cc's, Vespas, Enfields, 125cc's,regular road bikes up to specialized dual-purposebikes, big Beemers or R1's. What matters is your attitude and preferences. A JH600 I think could go around the world without any mod. But then there are the "always need to improve", play, fun, showing-off factors,...

Enjoy your ride!
AW.

Agree completely... and I am into improving a ride somewhat to my liking, not for the bling purposes that some might

[Pfaelzer]

Agree completely... and I am into improving a ride somewhat to my liking, not for the bling purposes that some might

...know what you mean, I'm sometimes a bit "over the top", right? But I like playing around with the bike and see what I can turn it into. Met a bunch of nice guys through the postings too, so I'll continue...AW.

[TexasAggie]

Phaelzer,
Can you tell me the bolt size you used for the rear shock? I am going to the states and think I will get a few high grade bolts there to bring back with me. My 127kg arse will stress any bolt and I would like to make sure I get good replacement on there. I do not have reliable source here in Nanjing for this.

DT

[Pfaelzer]

Hi,
finally I took the time to look more into the details here. One reason for the sudden hurry is, that some of you have decided to go for this modification as well.

The plan is, to measure the original spring and fork details, give it to Wilbers and ask them to suggest a spring - hopefully from their stock, for the JH600. The coil of the original spring has a linear design, which means that the stress is increasing linear to the load. This can be problematic, in case of extreme stress peaks during for example off-road riding. Hitting a pot-hole, the load becomes so high, that you basically would need stronger spring, so that the front doesn't bottom out. That spring would be too strong for regular use. The compromise here is a progressive spring. These springs do not have a constant spring rate but the rate increases with the load.



Progressive springs. You can see that the coil is getting narrower at one end.



Opening up the top is easy. The spring is being pushed down by the screw with a spacer. This is good news. It will give us more room with the choice of replacement since we can vary the length of the spacer accordingly.



There is a washer on top of the spring. I pull the spring out with a wire.



Measurement of spring-load to top of tube: 15mm.



Here the complete assembly.



Here I measure the oil-level inside the tube.



The method is a bit rough but the level is at around 290mm measured from the bottom of the tube.



Here some of the main measurements of the original spring:

Lo (total length): 540mm
Do (outside diameter): 34mm
d (thickness of wire): 5mm
Di (inside diameter): 24mm
m (coil space): 13mm
Number of windings: 40
Inside diameter of fork tube: 35mm
Length of spacer: 150mm
Washer thickness: 1.5mm
Height of threat of the cover screw: 18mm
Inside depth of the fork tube: 680mm - totally decompressed
Fork travel: 170mm - 180mm (based on manual)
Pre-load: 15mm to top of tube + 18mm thread of top cover screw = 23mm total


Here a testing set-up to measure the spring rate.



The spring is now inside of the lower tube. The upper tube acts as a piston, which loads the spring with different weights.



Here my laboratory working table with all tools and notes...

Oh, the calculated test result after averaging four different loads is 8.2N/mm (spring rate).


Well, now I will try to contact Wilbers, give them the link of this post and then let's see what they are coming up with. Stay tuned for more to come here... I'll go to the workshop and put everything together again.

2010-04-27 Update

Talked to Wilbers and they needed one more information about the sag of the bike with an without rider. We measured like that:



Sag unloaded: 17.9mm
Sag with rider: 41.2mm (riders weight 95kg)

Referring the problem, that the front bottoms out during hard riding, there is the possibility to add more oil into the front fork, which reduces the air volume and therefor makes compression harder. The critical measurement here is actually to be measured from the oil-level up to the cover of the tube without springs in the tube.

At my bike I measured: 390mm

NEW! Just received information from SHOWA through Franki on the oil capacity used in the original fork:
- Fork oil SS-8
- Capacity for X02(Domestic Model)：534 ccm and for the X02C(Euro Model)：599ccm +/-2.5cc

However, since there will be different springs inside of the tube, the oil volume will need to be adjusted. I decided to measure the oil level, with the spring inside.

I have also decided, to put those good looking rubber boots on the fork, this means that I have to disassemble the complete front.



Looks a bit "handicapped"...


Here the comparison of original and progressive spring


SURPRISE! Check out the different colors of the fork oil, which I took from the left and right tube...

It made really sense to change the oil.

Here the oil I have chosen for now:


Despite of previous informations, I took almost exactly 500 ml out of each tube.


I measured now the oil level in the tube, fully extended, without spring of 180mm from the top. With this nice tool I can set the new level precisely.


Fill up a bit over the measured volume...


...and suck the excessive oil out again to the right level.


Fit the boot


Front end assembly


The new look


First test ride feels more balance and solid. I have to go a bit more off road, to see if the front bottoms still out or not. After that I will decide to add some more oil, or maybe take some oil out to maximize travel.
Considering the relatively low costs and easy job, it is recommendable to do this, especially in combination with a stronger rear shock or traveling fully loaded. I have a eastern ride ahead of me. After that I can let you know some more road experience with this modification.

Will keep you posted.
Cheers, AW.


...back to modification list.

[TexasAggie]

You have more toys in your lab than I do in Texas and Nanjing combined. You are winning.

Keep me posted. I ordered rear spring/shock assembly and front springs from Franki. I am sure you two are in communications. I can wait till new changes are confirmed to work. Nice to have you doing the R&D. I owe you lots of beer or wine!

DT

[Pfaelzer]

Phaelzer,
Can you tell me the bolt size you used for the rear shock? ... DT

TexasAggie,
The bolt is a M10. Important is that the head and the nut are not taking up too much space. We have about 12 - 15mm room at each side. What you can't see on the picture is, that the complete lever mechanism is a bit moving to each side - not really stiff. So You need to have some mm room between the bolt/nut and the outside levers. Hope this is somehow understandable...
AW.

[TexasAggie]

Very clear. I am familiar with the Honda suspension on y Baja bike. This sounds very similar. What about the bolt length? I think I can buy some low profile bolts that would work.
Thanks again
DT

[Pfaelzer]

.... What about the bolt length? ...DT

Well, the outside dimension of the fork is almost 41mm. Then you need 3mm for 2 washers, at least 8mm for the nut, that makes 54mm (M10X55 would be the choice then). Last time the Wilbers guys were not able to incorporate a thread into the fork, which would make things less tight. Make sure you choose a bolt with a rather low head hight. I milled all down a bit to get more room.
AW.

[TexasAggie]

Great information, I saw it looked like you took a mm or two off the head. I can work with this information for sure. Thanks.