Sudden loss of clutch lever pressure

[hooptygoo]

This is a weird issue I've been having recently. For the most part, my clutch is great - the lever feel is perfectly firm as it should be, not spongy or anything to suggest needing a bleed. Actuation is smooth, engagement is complete, shifts are easy and clean, etc....

Then suddenly (and randomly) I go to shift and there is zero pressure at the lever. Or sometimes there is pressure when I go to pull the lever in, but not when I release.

After this happens once, it goes back to normal perfect clutch mode for however long it likes. For example, on yesterday's 200 mile ride it happened maybe 10 or 15 times. It never (at least so far) happens twice in a row and I can't intentionally reproduce the effect.

What does this sound like to you? It started happening before my last fluid flush and bleed and it seems like it's getting worse. I would think if there was air in the line that it would always be kinda spongy and not suddenly drop out only to instantly and fully come back. Could the push rod shaft be binding on something? I would think normal operation would be less than smooth if this were the case. Maybe a failing cylinder - either master or slave? It reminds me a little of when the rear master on my Sportster was dying - sometimes I had brakes, sometimes I didn't. After a rebuild it was perfect again.

Is it time for an Oberon or EVR upgrade?

Thanks all.

[johnchypermotard]

i have had this same issue come up on my hypertard ... each time it does, there has been air in the line.

i have had success at fixing this by bleeding the clutch master at the top ... bleeding the slave does not seem to fix the situation.

give it a try ... takes but a few minutes to bleed the top of the master ... just apply slow, even pulls on the lever, bleeding when lever is fully pulled in.

hope this helps.

ciao,
johnc

[hooptygoo]

Sounds like a good place to start. I'll try that and report back.

[08hyper]

Johnc is right, bleed your master cylinder first, then the slave, check your hose connections.
The bleed on the master can be trickie, I sometimes will let the lever slap a few times to dislodge any air bubbles. Aloha Alex

[freezer16801]

also check that the slave is properly tightened to the engine case. If it has loosened and the shaft isn't coming completely in contact with the slave, you could get this type of reaction. I am betting on air in the system. I am just offereing up some other ideas if air isn't the culprit.

If you don't have fluid leaks, no air in the system, and everything is tightened, your next step is faulty parts.

[Bmgonsf]

Originally Posted by hooptygoo

This is a weird issue I've been having recently. For the most part, my clutch is great - the lever feel is perfectly firm as it should be, not spongy or anything to suggest needing a bleed. Actuation is smooth, engagement is complete, shifts are easy and clean, etc....

Then suddenly (and randomly) I go to shift and there is zero pressure at the lever. Or sometimes there is pressure when I go to pull the lever in, but not when I release.

After this happens once, it goes back to normal perfect clutch mode for however long it likes. For example, on yesterday's 200 mile ride it happened maybe 10 or 15 times. It never (at least so far) happens twice in a row and I can't intentionally reproduce the effect.

What does this sound like to you? It started happening before my last fluid flush and bleed and it seems like it's getting worse. I would think if there was air in the line that it would always be kinda spongy and not suddenly drop out only to instantly and fully come back. Could the push rod shaft be binding on something? I would think normal operation would be less than smooth if this were the case. Maybe a failing cylinder - either master or slave? It reminds me a little of when the rear master on my Sportster was dying - sometimes I had brakes, sometimes I didn't. After a rebuild it was perfect again.

Is it time for an Oberon or EVR upgrade?

Thanks all.

I had this as well, bleeding the master and slave would fix it for a short time (I had a DP Slave) but then it would happen again. The only 100% fix I have found is to replace the slave with a STM slave. I went through 3 DP Slave cylinders before my dealer said thats it and put on an STM....NO more clutch issues.......

[hooptygoo]

So, I bled and bled from both bungs and still couldn't budge no bubbles. Seriously, I got nothing except a little bit of black stuff when bleeding from the master. Lever seems perfectly firm but I haven't been able to road test since most of California has been under water for the last two days.

New question though... When capping up the reservoir, I noticed that I could get almost (if not all) the air out by filling it close to the max line, replacing the rubber insert thingy and by carefully pushing the center of it into the reservoir until there was no bubble left - then replacing the cap. Do you guys do this? Is it necessary. It takes a little extra care and time but it's also pretty easy. I'd think the less air in there the better. Mountain bike hydraulics are completely devoid of air in their systems so why not on motorcycles?

[08hyper]

I would leave a little "air" space in the reservoir especially on the brake side, remember that when the fluid gets hot it will expand a little, and the air space will give the fluid a place to go, if there is no air space, the fluid can press on the pistons and cause the brake pads to drag on the rotors. Aloha Alex

[hooptygoo]

That make's perfect sense. Although when I think about it, that rubber stopper and the air on the other side (between the stopper and the cap) are still just as compressable as if the air was inside with the fluid. This way, you just don't have fluid sloshing around in the bucket.

[08hyper]

That is true, but there may not be enough air space behind the rubber seal & cap, and if its like the brake cap on the cars, its job is to expand & follow the lowering fluid level and help not allow air into the system. Aloha Alex