motometal

LIFETIME SPONSOR
Sep 3, 2001
2,682
3
I am working on the forks on my XR650L. It has conventional cartridge Showas.
The forks seemed to blow through the travel too quickly, and the compression clicker was full hard. My wt is about 155 and the bike is used mostly for street riding but must also take the punishment of some decent sized jumps at the local mx track (these bikes were made for that, right?).

I am noticing that there is "negative preload", that is, there is actually a .5 - .75" gap between the fork spring and the cap! All of the forks I have worked on (altough I have never worked on an XR) had either zero or a small amount of preload. What gives?

The free length of the spring is well within spec. I am putting in 10 wt. oil (stock is ss-7), with the idea of making the forks a bit stiffer overall, hopefully this is ok as there is no rebound adjustment. The forks contained about 530ccs of very ugly (stock?) oil, and the level was 6.25", spring removed and dampening rod compressed.

Has anyone had any experience with using chunks of pvc pipe for spacers? Did a search-no results. My concerns with this are: allignment of the spring with the spacer, and small shavings of the plastic getting in the valving.

Thank you in advance for you help with this heavy but very very fun to ride bike!
 
Last edited:

motometal

LIFETIME SPONSOR
Sep 3, 2001
2,682
3
oops, my bad, I see now that the dampening rod extends quite a bit farther once the cap is out of the inner tube, so actually the spring did have a bit of preload on it. anybody in the market for 2 pvc couplers? I paid 14 cents each for them, but at this point all reasonable offers will be considered.

any comments on using 10 wt? am I on the right track? is Showa SS-7 actually 7 wt oil?
 

bclapham

LIFETIME SPONSOR
Nov 5, 2001
4,340
0
moto: if its blowing through and the bike has some years on, then maybe the valving is crudded up. the thicker oil doesnt make that much difference either, i ran really thin stuff once to lighten the damping and it made little differnece.

i had some brass spacers made up on a lathe at my work machine shop, not sure about pvc though

i have a question for the experts, how much preload can i run on the fork on my 02RM showas, i will need to do this as a stop gap until i get stiffer springs
 

motometal

LIFETIME SPONSOR
Sep 3, 2001
2,682
3
turns out I didn't need the spacers after all, but a google search found many people recommending pvc spacers, no mention of problems. Remember though, adding preload just adds x amount of spring pressure, constant at all levels of suspension compression. So it makes the biggest % difference near minimum compression, and the least difference bottomed (so it isn't a good mod to prevent bottoming). A heavier spring rate is multipled throughout the travel, so the % increase (not the amount of increase) is the same anywhere in the travel. What is your goal with changing springs?

well, regarding the 10 wt. I had special ordered it, so I went ahead and put it in, we'll see how it works. The valving probably was pretty mucked up, lots of really black looking oil came out of these forks. I flushed oil thru the works until it came out clear, but wasn't able to take apart the cartridges.
 
Top Bottom