FE390 Clutch Fluid

JohnnyQuest · Mar 27, 2011

Went riding today for the first time in 2011. There was still some snow on the trails but it got all the way up to 36F so I couldn't wait any longer!

Anyway....

When I first started off, I noticed the clutch engaged very early (lever just barely off the hand grip). Soon I lost pressure in the clutch lever. I removed the cover, and it was nearly empty. Buddy had a container of mineral spirits. We topped it up and pumped the lever about 50 times. Bubbles eventually stopped and it seemed good. Off we went. About 5 miles more and I lost pressure again and the clutch wouldn't disengage when I pulled the lever in. I removed the top of the master cylinder again. This time it was still full. I pulled the lever maybe 2 dozen times and the bubbles stopped again. Rode it about another 25 miles without problem.

What do you think? I figure, I'll just carry a container of mineral spirits and see if it happens again. Is this a classic sign of the O-ring going? The bike has about 50 hours on it. This is the first time I had this problem and the first time I ever checked the fluid level.

berglsmerg · Mar 27, 2011

Sounds like you are filling up your gearbox with clutch fluid due to bad seals in your slave. Also to bleed the magura steup you need a syringe and a piece of tubing to put over the slave bleed nipple and push the fluid back into the master cylinder. Sounds crazy and backwards but it is the go.

n4hhe · Apr 6, 2011

I think mineral spirits is probably the wrong thing to be using. Mineral oil is specified. Many use ATF or fork oil with success.

MrSmooth · Apr 6, 2011

berglsmerg said:
Sounds like you are filling up your gearbox with clutch fluid due to bad seals in your slave. Also to bleed the magura steup you need a syringe and a piece of tubing to put over the slave bleed nipple and push the fluid back into the master cylinder. Sounds crazy and backwards but it is the go.

+1. Pushing fluid from the bottom up is the best way. I used Mineral Oil in my Magura clutch without any issues.

JohnnyQuest · Apr 6, 2011

Yes, I ment mineral oil. Thanks.

I bought the syringe and the tubing. Seems strange that I remove the bleeder, inject the fluid, and then reinstall the bleeder screw. Won't all the fluid drain out as soon as I remove the bleeder? If I leave the cap on the reservour to prevent the fluid from draining, how will I inject into the slave?

WoodsRooster · Apr 6, 2011

I used to replace the bleeder with the one in the kit but just this past weekend I discovered you can just crack open the bleeder and push fluid through it. First remove the cover from your master and I use a second syringe to draw the old fluid out until replenished with new fluid. To answer your other question you will lose a little bit of fluid by leaving it open on the slave but it won't pour out as you would think. You can then just top off the master if needed.

Make sure you are not losing fluid from your master. I was and I lucked out by just cleaning the plunger assembly and putting back together. No more leak. I thought I was going to have to replace the plunger assembly (approx $75) and/or possibly the slave.

MrSmooth · Apr 6, 2011

Woodsrooster is correct. Don't take out the bleeder. I do it just like he does and after I put the top back on the master I push a little more in. Clutch should be good then.

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FE390 Clutch Fluid

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