I need to rebuild my clutch master and I am getting a few different answers for the clutch fluid on my 630 . ATF ? Drugstore mineral oil ? Unicorn blood ? I am sure the dealer has something in stock for $867.84 an ounce , just want to hear what you guys have to say .
My clutch just shat the bed last night. 630 @ 5K. Pulled the cover and almost no fluid...no apparent leaks, so my guess is the slave seals bit it and fluid is now seeping into engine. I bled it and gave it a run and all works fine (used mineral oil, BTW), but I guess w/in the next few days I'll know if it's the slave (if still no apparent leaks then must be injecting into engine...someone correct me if this deduction has holes in it.) Don't know if I'll try seals or a new assembly. Bummer...hate the bike being down at the start of the season. On fluid- here's some info CJBrown posted...good reading: So I got my curiosity up and did some research on this and it has been discussed ad infinitem on ADV, to death really. All the KTM's and a bunch of BMW's have these clutches on them and there's all kinds of issues but nothing that isn't easily remedied. If you want a little reading or a LOT, just search on google like this: site:advrider.com mineral oil clutch - you'll get hundreds of discussion links. The hydraulic clutch is a closed system with close tolerences so a light viscosity fluid that is non corrosive and non seal softening or hardening is what's required since the pistons have o-rings on them to seal. The factory's idea was to make sure we didn't put brake fluid in them so they specified mineral oil. Magura Blood and Royal Blood is mineral oil. And Magura makes the same units for all of the BMW hydraulic clutches as well. Of course BMW has their own fluid too for like $22 for a couple of ounces. Mineral oil has a boiling point of 740deg and is non hygroscopic, which means it does not absorb water like Dot brake fluid does. Since the system is closed any light oil will work in them, fork oil, hydraulic jack oil, sewing machine oil, ATF, power steering fluid for BMW and VW, baby oil, even olive oil. The latter being less desirable for stability, and baby oil because it's purity and viscosity aren't well known. But lots of riders have been using pure mineral oil like baby oil or drug store mineral oil for years without incident. The Magura or Shimano (for bicycle brakes) are the right viscosity and so are obviously recommended. It is generally said that these system don't require any kind of regular maintenance nor fluid changes since there is no heat involved like for brakes, and no water gets in them. Of course it makes sense to check your fluid level so if the slave leaks you'll see the level drop so you can fix it before you are left clutchless.
Yep, after conversations with Xcuvator, and some of my own homework, I'm using Amsoil "light" fork oil as well. After having my clutch master apart and seeing the scoring, and reading many accounts of the same, the logical conclusion (plus reading spec sheets and white papers) is that mineral oil simply doesn't have the lubricity required for a long piston-cylinder wear life. I do not recommend using ATF due to the metallic particle content. I considered using jack oil, except that it's relatively heavy at a fairly universal 10 weight rating.
Ha, thread title caught my eye...and then find I was quoted.... When mine was brand new it started leaking out the piston at the lever. I would find a drop or two on the floor, then wet around the dust boot at the lever. Took the cap off and it overflowed, so I think it was over-filled at the factory, or never adjust when assembled, or something like that. And there was a lot of goo in the reservoir, not sure if it was moisture or what, looked like milky clear jello. I bought a pint of mineral oil at CVS for like $3 and sucked the goo out of the reservoir and topped it up with mineral oil. Have not touched it since, just about 5K miles now. Clutch is like butter, has never leaked again.
Well , I ended up with mineral oil . Couldnt find light fork oil anyway . Here is another question related to ''my'' clutch . What is the secret to bleeding it ?! The tranny was butter smooth before all of this started , now it feels like its hanging up , and cant find neutral with ease .
Sounds like you still have air in the system. The best way to bleed a clutch is to remove the slave and push the fluid up by pushing the piston. Works every time.
Yup. I gravity bled mine, then did the above. Got a few more pesky air bubbles out on the final backward surges.
I bled mine last night, top down, but then I didn't have any bubbles in it. I would imagine if you got air it it might be tough to get all the air out by opening the bleed nipple with a hose on it. I use clear tubing so I can see what's coming out. After all this discussion I got curious becuase I'm leaving thursday for a nearly thousand mile trip to remote hinterlands. LOL. My clutch better work. I had not had the MC cover off since the bike was new, so I got to thinking... Fluid was dark, almost opaque. So I siphoned it off and poured new in, then bleed out the bottom. Color wasn't bad at the bottom. All working good...glad I did that.
Well , I have bleed the thing to death and still get bubbles from the master when I clutch the lever. I have tried to push the piston on the slave , but that didnt seem to do much. Will keep at it now and see what happens.
If you are getting bubbles when you pull the clutch lever, you may have a leaky seal in the MC, but usually you will see fluid leaking out too.
The service manual says you need to pressure bleed it from the bottom up. Bubbles rise and the oil is light, so going down may be problematic. Could also be a leaking MC piston seal as mentioned, but I think it would leak out as well. Put a big syringe on a tube on the bleed nipple and pressure it up and out the MC. If you put new internals in it maybe it still just has air in it.
If you can't bleed by pushing the slave piston, your lever adjustment may be screwed in too far so that the MC outer seal is blocking the piston port in the MC.
I will try bleeding it from the bottom as well. I bought the MC kit from a reputable dealer , I would hope that they sell quality parts.
Usually reverse bleeding works for me .... If you can get any action out of the clutch, ride the bike some and then re-bleed ... Riding might help push the air out of some pocket it might be hung in ...
I will take it for a ride and see. Never had an issue like this come up , can't even compare it to anything.
