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Discussion Starter #1
Okay, so this is probably going to sound a little weird, but bear with me...

Figured this out one day on a trip up to Mt. St. Helens (beautiful ride btw). On a long straight I was resting my clutch fingers a little heavily on the clutch lever and noticed it started to disengage. Let me rephrase that... The lever began to travel, but the clutch remained engaged. I wasn't actually applying pressure on the lever (not intentionally anyway), but with just the weight of my fingers, and maybe a LITTLE bit of effort, the lever moved. After playing around with this theory, I noticed that if I moved the lever very slowly, even traveling at 60+ mph in 4th gear, I could effectively fully close the lever to the bars without any change in clutch engagement.

Now I have a theory on this, but I'm no mechanic, and I'm not sure how this will hold up, but here it goes:

Understanding that a hydraulic system operates by moving fluid from one reservior to another, translating lever movement through pressure to move some mechanism at the other end, is it possible to move the fluid from one res. to another with low enough pressure to not effectively operate the hydraulic system?

I could literally ride with the lever at the bars, and there was no change in engine response. My speed remained the same, and I could accelerate or decelerate with the same effect as normal, no obvious clutch slippage.

Maybe this is true of all hydraulic clutches, and I'm getting excited over nothing, but I thought it was pretty strange and wanted to clarify.

Any thoughts?
 

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It's not possible to move fluid and have no actuation. Instead of imagining a reservoir on the other end, imagine filling up a piston, even very slowly, it should still end up being pushed by the fluid. I'm not sure as to why this is happening to you, however.

If you pull on the lever normally, can you engage and disengage the clutch?
If yes, I'd figure that something needs adjusted, probably down in the clutch-area.
 

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Discussion Starter #3
Yeah, under normal operation everything works fine.

Although now that you mention it, I have noticed that if I am downshifting through several gears and use the clutch for engine breaking, if I don't let the clutch fully engage between gears (i.e. let the lever out to half-engagement then pull it back in and downshift), it seems to shorten the usable range of travel associated with my clutch position. It kind of builds up pressure into a smaller and smaller area until I can fully engage or disengage the clutch in an area of maybe 1/4 of full lever travel. After that though, when I let the clutch fully engage again, everything goes back to normal.

Like I said, if I operate it normally, I don't notice any problems. No slippage, no half engagement, no skipping / missing / or popping out of gear.
 

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I'm not too up on the clutch configuration and what-not regarding the innards of an MV, but if you've got a few hours, drain the oil and pop off the right casing and check out the clutch discs. See if they match what the manual specs say they should using a micrometer. Maybe your clutch is wearing strangely or something?

But from the way you describe it, I'd be led to believe that it's not that, instead it's the hydraulics... somehow. Definitely need one of them more tech savvy people to chime in regarding this.
 

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There are rubber seals inside your clutch master and slave cylinders. If those seals are worn, groved, degraded or installed incorrectly, the problem you describe can occur. Also if there is air in the sytem it can cause similar symptoms. Since you are not a mechanic...self described...I'd reccomend taking the bike to your dealer/shop and have them replace the clutch fluid, bleed thasystem and test it for degraded psiton seals.
 

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Discussion Starter #7
That's what I was wondering, if maybe MV has some abstract clutch / hydraulic config dissimilar to most japanese bikes that might allow for this phenomenon. I know it sounds weird, and I would never have guessed it would function like it does. All my other bikes have cable clutches so I have nothing to compare to. My Brute has only about 2k miles, so I'd be suprised if there's any excessive clutch wear, unless something's seriously wrong.

I might have to crack it open and take a look at the plates anyway though, unless I get a more definitive answer.

Anybody taking a ride soon want to test a theory?

I should elaborate on "slow lever movement." To initiate this scenario, the clutch lever must be pulled in very gently over a 4-6 second period while maintaining throttle position (under load of course). Obviously you'll know right away if it's happening or not, as a normally functioning clutch would cause slippage and your rpm would rise. Somehow my r's are stable. It's also strange how it requires very little effort. The lever seems to be guiding itself in, and I can feel the resistance to move lessening slightly as it progresses. If I give it too much assistance, it functions normally and will begin to disengage.

:ahhh: ??
 

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Discussion Starter #8
There are rubber seals inside your clutch master and slave cylinders. If those seals are worn, groved, degraded or installed incorrectly, the problem you describe can occur. Also if there is air in the sytem it can cause similar symptoms. Since you are not a mechanic...self described...I'd reccomend taking the bike to your dealer/shop and have them replace the clutch fluid, bleed thasystem and test it for degraded psiton seals.
Now we're getting somewhere. I planned to mention it next time I take it in.. I do wonder though if it's detrimental to ride it as is. I don't have any problems unless I perform the aforementioned procedure. My next service is at 3750mi. I believe.

I bought the bike used with 1700mi on it. It's was bone stock and supposedly never raced. I don't technically KNOW what the previous owner did with it, but I don't imagine he would have screwed this up, so I guess it's probably an assembly defect.
 

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The worst thing that can happen in the conditions you list would be that you would be unable to disengage the clutch to shift gears. "Blip" shifting works but isn't that healthy fo rthe gearing. Refresh the fluid and bleed the system and see if that restores a "hard" lever feel.
 

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A footnote: I wouldn't ride it until I got it sorted out.
 

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Discussion Starter #13
Thanks guys, I'll get it sorted out soon. Good to hear that nothing's majorly wrong.
 

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Leaking cups in the master cylinder (probably not a lot of air as that should cause lack of disengagement all the time). The MV system is no different from any Japanese or other hydraulic clutch. If it was the brakes you would feel the lever slowly sinking to the bars (or the pedal in your car sinking to the floor) as you held steady pressure. A quick pull creates adequate pressure to operate, but if you hold the lever in long enough you will probably start to feel the clutch drag as the fluid leaked past the cups back into the reservoir.

Of course...it could just be a lot of air in the system...I've been wrong before. Also look for fluid leaking from the slave cylinder on the engine (but I bet you would have spotted that by now).
 

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Discussion Starter #15
I haven't noticed any external leaks. I would imagine it's just air. It could be a bad seal, I'll find out either way.

Your description of similar brake pedal / lever actuation is exactly what I'm experiencing.

Then again, my issues with multiple downshifts without full clutch engagement sounds a little like the fluid leaking past / clutch drag you mentioned.
 

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Yup it's def the hydraulics. Clutch actuation is a fairly simple mechanical process. I will spare you all the obvious details but I would have to agree with "crash2much" and "silentservice703" it's either air or faulty internal seals. If you are loosing fluid in any way it's your seals. If not then you have air in the line for sure.

Imagine trying to move your hand quickly and then slowly through water, or air for that matter. When you engage the clutch normally you have enough resistance in the line to push that piston for that split second. When you do it slowly.... Well you get the idea. Bleed the line, I would bet my pucks that would fix it.

Or as the story goes.... Doc it hurts when I do this. -DOC- "Well then don't do that."
 

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Discussion Starter #18
If it's probably just air then I'd like to check it out myself. I'm not a mechanic in the sense that I haven't done a whole lot of maint. myself, but I'm very mechanically oriented. I work in a machine shop, have for years, (as relevent as that is or isn't... tool familiarity and manuf. procedures I guess) I work on eletrical circuitry a lot (welders, cranes, forklifts, etc.), carb cleaning and rejetting, and have been living around bikes since I was 4. I'm not at all afraid to tackle this, but invasive engine / trans stuff I would leave to the professionals. Mainly all of my bikes have been new and haven't required much maint. aside from valve adjustments, filters, oil changes, plugs, the basics.

I haven't bled hydraulic lines before however, anybody care to explain the procedure to me? If I need to add fluid, what brand is recommended?
 

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It is actually an easy process. Keep the work area and reservoir area and bleed areas CLEAN. I don't have my bike (312R F4) here for reference, so I can't go see if there is an upper (master cylinder) and lower (slave cylinder) bleed screw. However:
1) Using the appropriate size 6-point box end wrench, crack open, and then close your bleed screw(s). This will ensure free movement when you start the bleed process.
2) Clean, then remove the clutch master cylinder reservoir cover...set it down someplace clean.
3) Attach a clean piece of clear tubing that fits tightly to the bleed screw outlet port. The tubing needs to be long enough to extend to the floor where it will terminate in a clean clear container that has enough clutch fluid in it as to keep the hose end submerged for the entire process. The container needs to be large enough to contain the fluid you are going to bleed through your clutch hydraulic system. (About a quart sized container should do).
4) IF you have a buddy, it would help at this point, but it is not required...Exercise the clutch lever SLOWLY and hold it strongly depressed, then reach down and open the bleed valve a quarter turn...the clutch lever will collapse to the handgrip...hold it there…now close the bleed screw.
5) Slowly release the clutch lever. During that process you should see clutch fluid stream down the clear hose, it will probably be discolored (darker than fresh) and what you are looking to see is air bubbles being ejected as the process is repeated. Replenish the clutch fluid in the reservoir BEFORE it empties out (this prevents reintroducing air into the master cylinder). NOW repeat 4 and 5 until fresh fluid is ejected at the clear hose and no more air is seen, and then remove the hose.
6) Check fittings for tightness.

Once that is done, your fluid has been replaced with fresh, and hopefully all air has been expelled. If there is a master cylinder bleed screw, now is the time to give that a purge. Same process, fewer strokes.

When this is completed, you should have a solid hydraulic system with no spongy feel and the clutch should operate as new.

If your lever continues to drift toward the grip without actuating the clutch at that point, you have a seal problem and should rebuild the master and slave cylinders.
The recommended clutch fluid for my ’08 312R F4 is AGIP DOT 4, but any HIGH QUALITY DOT 4 should do. The fluid type for your clutch system will be written on the clutch master cylinder cover.
You don’t want to get any clutch fluid on any painted surface (it eats paint in time), be medicinally careful and clean.
 

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Discussion Starter #20
Sounds pretty simple, thanks for the walkthrough. I'll do it sometime in the near future. Probably not right now, just got 4 inches of snow today, on my long, steep driveway. Tends to create a little bit of work. I won't be riding any time soon in this weather anyway, but I'll get it taken care of.

Thanks again, and I guess all my questions are answered at this point.
 
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