Hydraulic clutches for dualsport dirt bike purposes

[wildwood 11]

I'm posing the question to our members vast motorcycle experience about the average life span of a hydraulic clutch for dualsport dirt bike purposes before major service is required.

I'm new to hydraulic clutches, and they seem great when they're working right, but once they begin to wear out it becomes a very inconsistent feel that fluctuates wildly between soft and normal. It's kind of a puzzling problem to troubleshoot. The one on my Husky TE310 has given up. Time for a repair/replace.

I've had to refill the Magura master reservoir for the forth time in about 1800 mi. of riding, refilling from bottom to push out any air. After servicing it felt good for a short time, then as time goes by sitting, you cycle the clutch lever and can notice it went softer. Riding it lately has the same result.

At the time the clutch really failed this last service, loosing the feeling of all back pressure, I had refilled the master reservoir and checked it, felt good. After 15 min. or so, soft mushy feel. Just checking things out, I adjusted the lever adjust screw in a bit farther than I ever had (but not totally maxed out) and after a couple pumps suddenly the lever went dead like there was no fluid in the system. The master res fluid level was down, but still had fluid above the intake. I'm thinking it's the slave unit because I haven't seen a lot of fluid up at the master and clutch lever area for what I've lost. Disassembly and inspection of both the master and slave units shows no obvious scoring or pitting on either bore. The seals have signs of wear under magnification, but no obvious cuts or cracks.

After more research today, it's been indicated that the Magura slave may be a little over matched by the Husky's stiff clutch spring, meaning to me that even moderate wear may cause the o-ring to allow loss of fluid or fail prematurely.

Both will be addressed at this point.

Checking web forums for input from other riders seems to point to the fact that hydraulic clutches on dirt bikes can be troublesome. Too abusive of an environment? Or worth the extra work rebuilding occasionally?

[mtnmanseth 0]

I was shocked to have to replace the clutch fluid in the Beta after a trip to Mammoth a few months ago. The bike was only a year old but after major clutch action loss (lever went floppy almost to the bar) while rock crawling at 9,000 feet my research taught me that:

1. Four strokes get so damn hot that the clutch fluid actually boils if contaminated with water
2. "Wait, how does water get in a sealed system like the clutch line?", I thought. Because it's not actually sealed... you all probably know this already, but there are tiny air gaps in the lid on the perch reservoir that allow atmospheric pressure to equilibrate as you go up and down in elevation. Water vapor get into the system through those holes, ESPECIALLY if you live/ride near the beach or relatively humid climates like San Diego
3. Okay, time to replace the hydraulic clutch fluid. USE BRAND NEW FLUID. Apparently, bottles of brake/clutch fluid are only good for maybe a few weeks after opening the bottle. Brake fluid is silicone based and hydrophilic (i.e. attracts water) so even just cracking the bottle will allow air vapor to "contaminate" the fluid. Your post doesn't indicate whether you tried fluid from a brand new bottle, but you might want to try that.
4. The higher quality/cost of brake fluid the higher the boiling point... Motul 660 (~$25 bottle) boils at 617 degrees F. That's what I put in the Beta and it's been back to normal for several rides.

You probably already know all this wildwood, but I didn't before I had similar clutch line problems so I figured I'd share with others. Since you don't perceive any detrimental wear to the individual pieces, could it be that you're using a bottle of brake fluid from 2005?

[paulmbowers 236]

Hold on- first determine exactly what fluid is used. Most often it is NOT brake fluid, and if you use brake fluid, you're likely to have a less-than-positive result.

Many use Magura "blood", or mineral oil or ATF or fork oil.

[PbdBlue 46]

Magura = mineral oil, Magura blood

Brembo (as in late model ktm 350/500) = DOT 4 or 5.1 (not 5) brake fluid

[dirt dame 559]

Put in an X-ring piston from http://www.7602racing.com/product-p/hus-cp01.htm. Your clutch fluid is leaking out of the slave cylinder probably. My cylinder wasn't even worn, but I was losing fluid into the engine. I replaced the stock piston with the 7602 one and have never had another problem.

[Sneeker 29]

My TE250 overheated once and cooked the slave gasket. Clutch hydraulic kept leaking out, no sign as to where. It took me a while to isolate the problem. But once I replaced that gasket, problem solved.

Tip:

The local Husky dealer wanted something like $35 for a new slave gasket. Instead I went to the local hydraulic machinery parts shop (Rupes Hydraulics), they gave me 5 free. A lot easier to troubleshoot at that price.

[wildwood 11]

Seth - I've learned my lessons on brake fluid. Read the fine print. DOT4 grades can vary greatly on max temp. It's been Motul 660 only in my equipment for some time now. Worth every penny. Magura's use mineral oil, which simplifies things.

​PMB - I just read about using fork oil, ....promising. It's a light weight to maintain easy pull, and has qualities to keep o-rings fat for optimum seal. I will be looking into that.

Mimi - I found that part earlier today too, thanks. It must be popular because it's out of stock right now. Need to call them and see what's up. It looked thicker and I wasn't sure if it worked at the same tolerances as the OEM. Good to know it does.

I feel like I've been online for days trying to find good options.........wait, I have been online for days...Uuuhh!

I've now got a stock slave piston coming ($75, ouch), and I'm going to take my old clutch master piston to Motoworld and cross check it with a KTM part (Magura Master rebuild kit for 9.5mm bore, PN:0720555 (KTM PN:59002********) Hopefully it'll work. Thanks for the info, very helpful

[wildwood 11]

My TE250 overheated once and cooked the slave gasket. Clutch hydraulic kept leaking out, no sign as to where. It took me a while to isolate the problem. But once I replaced that gasket, problem solved.

Tip:

The local Husky deal wanted something like $35 for a new slave gasket. Instead I went to the local hydraulic machinery parts shop (Rupes Hydraulics), they gave me 5 free. A lot easier to troubleshoot at that price.

I thought about going that route, but I wasn't sure about how many variables could be involved with finding a suitable match. I'll have a spare piston now. Any idea as to size/type of o-ring? Or just take it to Rupes Hydraulics, right.

[dirt dame 559]

Mimi - I found that part earlier today too, thanks. It must be popular because it's out of stock right now. Need to call them and see what's up. It looked thicker and I wasn't sure if it worked at the same tolerances as the OEM. Good to know it does

It was purposely designed to be thicker to work better, and decrease cylinder wear, along with the wider X ring. It is a definite upgrade.

[Bp619 104]

Bob try calling gp motorcycles. When my husky 630 slave went out they stocked a upgraded zipty housing and a better piston Oring combo. Dunno if same ezact part as your 310 but worth a call.

[robertaccio 406]

I will throw my hat in this ring although I have sworn off these things,,,,,,I have mega experience with the Italian Husky juice clutches.

DD spot on, use whatever is the OEM fluid you can order Magura Blood or motorex equivalent don't reinvent the wheel on OEM fluid, because its Hyd you could theoretically pee in the reservoir to make it work..use the OEM recommended fluid they designed it that way. all over the internet everyone wants to reinvent the wheel use the oem stuff.

7602 slave piston is great mine all had it. but be super sure that the cylinder is not excessively worn.

Master side you can order rebuild kits on line the cyl bore is numbered on the cylinder assy ex. 9.5, 10 etc in mm just to verify.

NOTE: carefully inspect the master cylinder bore for flaking of the plating material it should be smooth as glass, if not you will need a new master. you can get them

I tried also a ZipTy Racing CNC machined Slave but actually went back to a used salvaged OEM slave. But the ZipTy slave is another option if you need a slave. there is also an active UK company that has machined slave cylinders if your is overly worn.

when servicing remember to NEVER squeeze your lever with the slave cylinder off unless you have the piston depressed (only then you can get a feel for the pressure). with the slave piston at full extension (off the bike and off the clutch pushrod) there is nowhere for the piston to go but to explode the snap ring and ruin the slave snap ring seat groove. Ive seen it but never did it, knowing the system.

Most of all it is super simple system its a fully closed loop Hydro system just slightly vented at the master cover.

Get the bleeder kit form KTM it is the best way to service and bleed these things, another trick I always did was to fill a glass bowl with magura blood and assemble my slave fully submerged for zero possibility of air pockets in the assembly.

I spent many hour screwing around with failed and close to DNF issues with these freakin things I had to make them bullet proof......funny how KTMs had the same system and none of my Kato friends had issues........

Please understand that my racing and riding you can multiply my above numbers a couple times over.

for your records

oberon I no experience but many swear by these guys

ZipTy is my Husky guru they were the Italian Husky factory race team here in the US weat coast

Factory Pro Kirk is an authorized Magura dealer and can get master cylinders as long as you provide the bore size

7602 Clay is super helpful guy and his products are top tier.

http://www.oberon-performance.co.uk/acatalog/Clutch_Slave_Cylinders_CSC.html

http://www.ziptyracing.com/husqvarna-clutch-slave-cover/

http://www.factoryproracing.com/Supermoto_Wheels.html

http://www.7602racing.com/product-p/hus-cp01.htm

[wildwood 11]

Bob try calling gp motorcycles. When my husky 630 slave went out they stocked a upgraded zipty housing and a better piston Oring combo. Dunno if same ezact part as your 310 but worth a call.

Brian - good info. GP was closed yesterday, and I've been grinding on this for days. I was getting a little impatient, went ahead and bought an OEM piston I found. I called ZipTy yesterday to check on crossover application for that part. I haven't heard back from them yet, but I believe it is the same after cross checking other models. If this happens again in the near future, I plan to try these 'harder' parts now that I've heard experiences from people I trust.

Robert - Thanks for putting all that info together. I've visited most of those sites over the past couple days. I like having an honest account of performance before spending extra dollars for these upgrades. While reading a bunch of other forums looking for information, I noticed that you and Mimi had both commented on this topic around 2011. So your experience in this is pretty deep by now. Question: Have you converted your bike's to a cable system now for durability?

I'm using Motorex Hydraulic Fluid 75 Mineral Oil right now. From what I understand, these are 'hydraulic' mineral oils that are specially formulated, vs. 'pure' mineral oils that may have eventual issues if used for this application. I was wondering about the different viscosity of oils that could be used. Would a heavier viscosity (thicker) oil be harder to push past a seal than a thinner oil? It would surely affect the pull on the clutch some.

[robertaccio 406]

the motorex is a good to go choice I have a couple of those on the shelf next to a big container of Mag blood. I recommend only your motorex75 or actual magura blood per the engineers that designed and tested the system.

Once you get the system sorted it will serve you well. again many make it complicated just be sure all the components are good,

heres a good test procedure, after doing all your proper assembly/bleed before installing the slave onto the crankcase- let it hang- manually squeeze the slave piston in until it bottoms or at least gets some distance in from the snap ring stop. while holding the piston with your thumb, gently squeeze the lever. I did this solo all time left hand on lever right thumb pushing piston in. feel the pressure against your thumb and fight it while watching for any fluid leaking past the slave piston seal--THERE SHOULD BE ZERO leakage. This a quick way to test for leakage at the slave build as much pressure as you can without letting the piston be pushed back to the stop to get a good test. Think about the system and the actual pressure when its pushing the pressure plate release rod it quite high to overcome the clutch pressure plate springs. This way at least you get a warm and fuzzy before installing the slave back on.

Again I reiterate thoroughly inspect the Master for any cylinder damage, there can be ZERO allowance for any cylinder damage of the plating or you will get fluid bypass at the master cylinder piston.

Quick thought check, back to initial trouble shooting

If you are actually seeing fluid loss but not seeing any leaks outside the slave cylinder----the only thing it can be is the slave piston seal leaking, that fluid ends up in your crankcase with your oil.

If you are seeing no fluid loss but have a weak clutch or intermittent operation your looking at air in the system 1st check( not a real fail, but a problem), or for a fail you're looking at fluid bypass at the master cylinder piston, rebuild kit and super inspect the cylinder is where you go with that.

Additional the race teams from 06 and on with the twin cammer 450/510 series bikes fitted a simple hi temp o ring onto the push rod at the slave end that fit into the shaft journal to eliminate shaft vibration, this is just a supplemental racing trick, all of my 450s (TC,TE and TXC) had this.

PS all this is contingent upon that your clutch is mechanically sound from the start meaning plates and springs are in good order.

[robertaccio 406]

more came to me

If you use a ZipTy Slave assy use the OEM piston (per ZTR engineer, they only tested and used the OEM piston on all their 450/510 race bikes with their slave cylinder)

but for sure install the upgraded X-Ring to the OEM piston so you get good 2 position sealing

If you have a good OEM slave cylinder then you best use the 7602 slave piston upgrade.

I found some slight wear in the slave was inconsequential, but I would wary of a lot waer on 1 side of the cylinder making out of round. The good thing about the 7602 psiton is that the seal position is actually differenent on the cylinder wall than the OEM piston, that said so if the stock piston created wear the 7602 upgrade will be on the non worn cylinder wall. ( a little more science about the 7602 Piston

[wildwood 11]

Really good info your giving out there Mr. Nantista, much appreciated. I did a very close inspection on both master and slave cylinder walls, no sign of wear what so ever. I'm pretty confident they're not the issue. I put a rebuild kit in the master, it's ready to go. I should have a new OEM slave piston in tomorrow to get things back together. I will then try to get a 7602 piston for the next upgrade, and when the slave housing begins to wear, replace it with a ZipTy unit.

My gut feel after troubleshooting is that it was the slave piston o-ring that was allowing the fluid loss. Very little oil was around the master or outside the slave unit. During TS'ing I was pushing in the slave piston then sealing the inlet with my thumb and releasing the piston to see if it would hold vacuum in the chamber, and it did not. The o-ring was visibly worn, but no cuts.

I'll put your tips to good use. I did notice some excess play with the push rod, I will surely put your fix to that. Hopefully I'll have this completed before the weekend. Thanks to all for the input. Good stuff.

[Uncle Champ 116]

Hey Wildwood remember Porter Friend is right down the road from you, he loves Huskys and is an absolute guru on them, I know he is hard to pin down but well worth the effort.

[wildwood 11]

Hey Wildwood remember Porter Friend is right down the road from you, he loves Huskys and is an absolute guru on them, I know he is hard to pin down but well worth the effort.

Please PM me his phone number, just in case. I got my last part today, it's on and I'm bleeding the system now. Looks promising, should be good to go.

[robertaccio 406]

Yes Porter loves Huskys but I think we are talking Swede Huskys in regards to Porter. He's built some serious racing long lasting Swede Huskys back in the day. But what do I know, maybe he's all over these newer Italian ones as well.

He built a friend's aircooled 390 that we all bet against at how long it would last in the 24 hours of Fud (year I forget), the longest bet was for 8 hours until destruction........we all lost, the Porter built machine went 24 hours and I even rode it at Carlsbad months after and it went strong for months maybe more after with no rebuild.