Clutch woes... (keeps going spongy)

Urgh it seems like this issue just won't end. When I bought the bike it had a cracked slave cylinder, when the lever was fully in to the bars it would leak fluid into the gearbox. I replaced it with an Oberon billet aluminium one. And it seems that EVERY time I go offroad the lever goes to shit whereby its completely spongy for 1/2 to 3/4 the travel and effectively becomes useless. Pumping the lever several times returns it to feeling and operating like normal, but once it starts it continues to happen very frequently (seconds to minutes). It's particularly bad on hills either up or down, or just when hitting the throttle really hard
I keep thinking theres more air in the line, so I keep bleeding it and it works fine on the road. But every time I go offroad it plays up. It seems strange that it only takes a few pumps of the lever to make it feel good again, and then it goes to shit really quickly afterwards. So maybe there's something else going on here

If there was air entering the system i'd imagine that simply pumping the lever will do little to nothing in resolving it, and it would never feel normal again - only getting worse until it stops disengaging the clutch entirely.
And the lever can go spongy even during a hill climb where I have the lever pulled partly in, slowly but surely engaging the clutch even more, requiring more travel to overcome it. I've had a few times where the clutch is right in to the bars and the bike stalls, causing me to have to abandon ship and drag the thing back down the hill (I like super steep climbs)

Maybe something in the clutch causing the pushrod to shift around?
Could bad MC seals cause this?

The only issues I've seen on those bikes in reguards to the clutch lever was a oRing in the slave unit but you changed that part out ... These HYDO setups are so simple there just is not alot that can go wrong ...

Air in the system can caught lots of weird action ... When you are bleeding on it, does air ever come out? Bleeding at the top banjo connection might be helpful ...

There should be more suggestions on the way ...

Yes I do still get some air here n there. But I also just bled my KTM300 clutch and there was a little air in that, but it was consistent it never sometimes worked sometimes didn't. It never changed in its feel. In fact after bleeding it feels worse, too stiff, thinking of putting some air back in there

It's just weird that it only seems to manifest itself when offroad where there are much steeper up and downhill sections, and i'm on/off the throttle a lot more. And its a massive change in feel. It goes from feeling really nice and firm to completely useless for 3/4 of the lever travel, then back to nice and firm after pumping the lever a few times

The effect is like what happens when you spread brake pads apart with a screwdriver. Nothing in the lever whatsoever until you pump it a few times then it feels good again.
That makes me wonder if something wasn't put back together right, maybe its nothing to do with the actual hydraulic part and maybe its in the clutch basket or something?

Actually here's a good question. Does the master cylinder on the 09's use the same seals/piston/etc as the KTM's? If I can't find a cause my next course of action is to rebuild the MC, but getting husky parts can be problematic, and i'd rather get it sorted tomorrow than have to wait a couple weeks for an order

That slave cylinder just bolts on as far as I know ... If you just stuck it on there and did not pour any oil in it before bolting it on, there would be a ton of air in there to get pumped out with bleeding ... I'd keep bleeding (at that banjo bolt and all over) and maybe purchase that small kit for the master cylinder ... There is always the reverse bleeding also ...

There is 3 different sizes of master cylinders. Did you reuse the stock slave piston? The stock piston is junk. A larger piston from 7602 racing with a quad ring instead of the o ring works better. You can get a master cylinder rebuild kit unless the bore is gouged. If you replace the whole master, get a standard magura, not husky specific. All you do is replace the cap with your stock one with the decomp lever.

hell no, that stock slave and piston went straight in the bin. Oberon unit comes with everything

I pulled the MC apart and its different to the parts diagrams. for one the piston is held in with a circlip and is inserted from the outside not the inside.
Looked at the diagram for my KTM300 and yep thats the one, identical aside from the cover. Can see some little nicks in the green seal. will post pics later. I'd say thats the problem

That sounds like that might be your problem. Mine gave me hell in every possible way. Got it dialed in now and hasn't given me any problems since.

Here's the seal in question. There seems to be nicks all the way around in it, the same as the one in the middle (above the big gouge). They almost look symmetrical and machined, but I don't believe the new one had any grooves in it (just threw it in quickly). If I had to guess, i'd say that a previous owner put brake fluid in which caused it to swell and warp like that...


And yes the rebuild kit is the exact same part number as whats on my KTM 300 - 59002032000
Absolute bloody rip off, $85AUD for essentially a circlip, plastic washer, spring and that cylinder with 2 seals on it. All I needed were the seals but it is only available as a whole kit, and the seals have a flared design so i'm not sure if regular o-rings would have sufficed

There's also this


Which is the hose that screws into the master cylinder. That threaded piece slides back and forth freely, when tightened down in the MC it will sit snug against the end. But that size gap looks suspiciously like an o-ring should be there. I can't see anything on the parts diagrams that would indicate whether or not it does. In any case I can't see a reason for it to slide like that on its own, and could imagine air getting past the threads and into the line. So I put an o-ring in there and applied thread sealant as well. I don't see how it could possibly cause any harm, only provide additional sealing

Is your breather tube that goes from the top of the cyl head to the air box clear and free of kinks?

umm how does that relate to a clutch problem, wrong thread? lol

Also I found this photo which shows those marks, so yes are they are supposed to be there, but the big rip obviously isn't so it needed replacing anyway

The line fitting in your last photo seals by the rounded male ferrule fitting being compressed against the female in the housing. No "O" ring is used.

Also if someone used brake fluid in place on mineral oil it will contaminate every seal and hose in the system. It softens the rubber and absorbs into it to later leech back into your fresh mineral oil. You might have future problems. A flush with brake clean or alcohol can help but if the brake fluid was in there long enough all the rubber parts will have to be replaced including the hose. The same holds true for systems that are supposed to have brake fluid and someone pours mineral oil in them.

I'd say brake fluid has been through it before, there's some paint corrosion on the master cylinder, bummer. And a friends husaberg I just went to flush that and the fluid was like black sludge, also paint corrosion and a hell of a lot of corrosion and rust underneath the rubber cover that goes over the brake hose fitting, obviously brake fluid was trapped there. It looks like both bikes use the same hoses. He's obviously going to need new seals as there's continually small bubbles coming up through the master cylinder as you pump the lever with the bleed nipple closed

My bike has had several flushes of mineral oil through it, so i'd say my shiny new oberon slave cylinder and piston will be fine, as will the new MC seals for a while
Wheres the cheapest place to get hoses from? I've used $20 chinese braided stuff before and its worked just as well as the $120 options. However they only come with banjo fittings on both ends, not threaded ones

It was mentioned above that these components are very simple and not much can go wrong ...

Those rubber seals can go bad on that plunger and I'm not sure if you can tell by looking at them if they are bad or not unless it really bad looking... Did it leak any on the bike? Since you have taken it apart, more air is in your lines ..Air is about the only issue that can happen here ... Other than putting fluid in there that is not what is listed on MC cap ...

Good luck ... And those lines are nothing special and you should be able to get some made at some shop ...

Ride Safe Amigo!

How crucial is it to replace the line? Seems rather excessive to me. If it's one of those 'it may cause an issue, 6 months down the track' kind of things then I don't care i'll just replace the fluid every month with baby oil (which is 100% mineral oil), hell of a lot cheaper than replacing lines.
As shown in the picture above I could clearly tell an issue with the MC seal once I looked it, big chunk of it missing. But no, no fluid leaked out anywhere
In my experience with brake systems, air in the line will often cause the lever to either permanently be spongy, or it'll be spongy once in a while such as after sitting overnight. But it doesn't rapidly fluctuate between spongy to the point of being practically useless, and feeling perfectly fine and back to spongy again all within the space of a couple minutes

Is there any scoring on the inside of the master cylinder where the piston rides. Mine had very small gouges that wouldn't seal. Also for fluid, singer sewing oil is pretty much the same as the magura blood or the motorex mineral oil. At walmart a bottle is $2-3. Good luck, it's a bitch!

Hydraulic clutch systems should be bleed from the bottom up. You can buy a kit for cheap online or im sure at your local mc dealer. Usually Comes with an adapter to attached to the bleeder valve, clear hose and a large syringe.

http://www.motoparthub.com/0720568_...Mgl2cvrJGNoXDgVlD9_GHvql8-tRy9-TJ0aAtge8P8HAQ

It may or may not relate to your clutch prob. If the breather tube is obstructed, pressure builds up in your engine and pushes back against the slave clutch piston. It happened to me.

Yep, like huskyista said there a tiny hole that vents the fluid back into the reservoir and if you adjust too much free play out of your clutch it will either pump up and make your clutch slip or it will not let fluid back in and your lever will flop and have poor pressure.

Had a similar issue as you describe. My Oberon seals were at fault. They said They were compatible with mineral oil, but they were not. They would be fine at first, but when out racing, my clutch would sponge out.Ty and I installed New seals and I had no more issues. It was that green seal btw.