Fork Fluid
 

I was going to do a simple post in "What did you do to your RX3 today" but thought I'd start this instead.

Has anyone here changed their fork fluid yet? I did yesterday. Got bored, all three of my Penske Boyz were knocked out of the NASCAR race so I thought no better time to gut the front off the RX3 and do the fluid.

Now....with the TT250, I recorded 320cc's drained from each tube. Makes sense because they're rated at 330cc's and there's always leftovers inside unless you do a complete teardown.

The RX3 forks are supposed to hold the same amount (330cc's), according to the CSC tutorial. Now, just like the TT forks, the RX3 forks worked well enough, but had that harsh little bit at the first "bounce" of travel that you could feel in your wrists and elbows. Nothing big but it was there, nonetheless. Other than that, I was happy with how they handled the rough stuff and twisties.

Well, well.....I was only able to coerce 250cc's from each fork tube....and they're supposed to be holding 330cc's. I understand that there will always be some left inside, lining the tubes, dampening rods, springs, etc...but 80cc's?

Anyway, I refilled with the same amount (250cc's) of Bel Ray 10W (I'm currently 220 lbs) and went out for a burn. That first little harsh bit, gone. The forks now eat up all the little stuff the road feeds them. Even with the odd "lesser amount", they feel just fine.

Anyone else had this experience with the fluid volume? Unless there's some "mystery chambers" that are holding upwards of 80cc's of fluid, they seem to work just fine with the amount I refilled. I surely didn't want to overfill them.

Thanks for the post, 2LZ.

I haven't replaced the fork oil yet, but have been thinking about it.

The front end of my RX3 has a "jittery" up and down motion to it.

I was hoping new fork oil might cure it.

And mote than likely, the new fork oil would be a better quality than the factory oil.

What weight oil did you use? Did you flush out the old oil with ATF fluid?

jb

I've been strung out on Bel Ray 10W since my young MX days. It's all I've ever run. I used to use ATF as a kid but once I got more aggressive, it would foam and blow up the forks. I don't ride like that now but I've never had any bad results with the Bel Ray.
The biggest thing I noticed is now the forks really function in that first 1-2" of travel. Eats up the small stuff now.

I didn't flush them, just let them ooze for a while until they dripped at least 50 times. I flipped them back and forth a couple of times looking for that mystery 80cc's but both forks acted identically.

Typical RX3 though. Compared to the smaller bikes, it's a pain to wrench on. You have to remove the cowl around the ignition just to get to the upper tree bolts and you have to undo all the plastics and pull them away from the tank to access the lower tree bolts. As usual, it's the plastics you spend a bunch of time on, not the actual project.

i know spud man used mobil 1 synthetic atf in his forks there is a thread someplace on the different amounts of oil people were getting in there

2LZ,

Had near enough the same thing a while back,

See here http://www.chinariders.net/showthrea...591#post195591 and my following posts in that thread :)

Thanks katflap! So much for my "search" talents. Sheesh... I must have spelled it "ferk erl" or something like that. ;-)

I see that there is an internal cartridge that holds the mystery 80cc's. Good to know! Still a nice improvement with the new stuff in it, for sure. More forgiving to the elbows and wrists in the light bumps.

2LZ,

I thought measuring the height of the oil in the fork tubes was the traditional way of measuring the correct amount.

Am I missing something?

jb

That's with conventional forks. The RX3 has inverted or sometimes called USD (upside down).

Thanks, haven't had to change fork oil in usd forks before.

jb

Since CSC was kind enough to supply us with a measurement in cc's (and fl oz) in the tutorial, that at least let me know what's "too much".

Generally speaking on USD's, if I'm not completely disassembling them and changing seals, I usually put in what I take out, if they both measure evenly.
Out of all my CB's, only Q (Q Link), the TT250 (Zong) and now the RX3 (Zong) have had the same amount in both forks! Makes it easy guess work.

How do you know if there was the correct amount of fork oil To start with?

I'm currently changing the fork oil in my TW200 (long overdue), and the amount of fork oil was not anywhere near what the manual calls for.

jb

You mean to tell me a Japanese bike didn't come with the recommended amount of fluid in them!? ;-)...either that or your seals are leaking???

Are you gutting them completely and replacing seals and bearings? If so. I'd do the recommended amount. If you're just dumping them and refilling (on normal forks), I'd do the measurement from the top without springs if you have that stat. Then you know it's correct.

No evidence of seal leaks on the TW, just dumping and refilling.

I've done this job on "right side up" forks many times.

Yes, having the wrong amount of fork fluid from the factory is not uncommon on TW's.

What I'm wondering is how do you know if the amount of fork oil in USD forks is correct from the factory if you only replace the amount of oil that comes out?

jb

I have to second this question. When I drained the forks on my Qlink XF (when I had it), I got 330 ml out of each fork just like the specs. said I should have.

Hey I can chime in here. I just changed mine recently. I couldn't find Mobile 1 ATF but I used another well known brand I can't quite recall. But I also used the synthetic ATF. I let my forks drain for a couple of days and got 325 CC's of fluid out of each one. After changing the fluid the sharpness did go away a little. Certainly better than stock.
Hope yours get better as well. Good luck.