clutch holding for 10 sec

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D-Max2012

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Well, Just changed out the old stock clutch line to braided SS, after having my clutch lever loose its pressure if held in for 40 seconds or more, in 1st gear at a light. Then the back tire starts to move and I had to shut the bike off to get back into neutral.

After the SS line is in place, now it only keeps lever pressure for about 10 seconds..

The old fluid was very dark, like mud, before working on it today. It looked OK in the sight glass but after it lost pressure multiple times 2 weeks ago, I parked it.

I used the mighty vac to try and suck any air from the bleed screw, near the clutch cover. This looks to be harder to do than the brakes, because the clutch has a spring in the system. So feeling for that No-More-Air, hard lock-up point, while pumping up pressure, is hard to feel for.

My question is, What would cause these symptoms?
1) Hold the clutch in,, you start to feel the amount of force needed to keep it depressed, diminishes after 10 seconds. If in 1st, the tire starts to grab.
2) No visible leaks anywhere.

If the piston, inside the clutch master cylinder, is in a closed system,,, could there be a micro hole or problem with the 0-rings, allowing fluid to seep back into the reservoir?

I'm trying to figure out why it feels like a pressure leak, but there's no fluid leaking anywhere.

What do you think?
 
Well, Just changed out the old stock clutch line to braided SS, after having my clutch lever loose its pressure if held in for 40 seconds or more, in 1st gear at a light. Then the back tire starts to move and I had to shut the bike off to get back into neutral.

After the SS line is in place, now it only keeps lever pressure for about 10 seconds..

The old fluid was very dark, like mud, before working on it today. It looked OK in the sight glass but after it lost pressure multiple times 2 weeks ago, I parked it.

I used the mighty vac to try and suck any air from the bleed screw, near the clutch cover. This looks to be harder to do than the brakes, because the clutch has a spring in the system. So feeling for that No-More-Air, hard lock-up point, while pumping up pressure, is hard to feel for.

My question is, What would cause these symptoms?
1) Hold the clutch in,, you start to feel the amount of force needed to keep it depressed, diminishes after 10 seconds. If in 1st, the tire starts to grab.
2) No visible leaks anywhere.

If the piston, inside the clutch master cylinder, is in a closed system,,, could there be a micro hole or problem with the 0-rings, allowing fluid to seep back into the reservoir?

I'm trying to figure out why it feels like a pressure leak, but there's no fluid leaking anywhere.

What do you think?



Sounds like you need to rebuild you master cylinder for the clutch.

I routinely hold my clutch lever in at every light - for as long a needed with no issues.

Sounds like the internal seals are letting pressure drop. Nothing to do with your new SS line.


Sent from my iPhone using Tapatalk
 
Sounds like the internal seals are letting pressure drop. Nothing to do with your new SS line.

I plan to try again tomorrow morning to see if i can coax some more air out of the line.

I was wondering if something is failing with the piston and seals (o-rings)..
clutch handle.jpg

BlaxMax,,
You can see it fail in the 2nd video I posted.
 
Possible internally-bleeding master cyl & air left in the lines. Do the reverse-bleed w/a 60 cc syringe pushing fluid up from the clutch slave cyl bleed valve, and rebuild your master cyl or replace it w/a new one.

From another thread about bleeding:

I use a short piece of clear plastic tubing and a syringe I buy at the pharmacist's, you don't need a prescription for a syringe, it's a 60 ml (CC) syringe w/a conical tip on it which accepts the clear plastic tubing I.D. tightly.

If I am installing a rebuilt slave or a new one, I fill it w/fluid on the bench, hand tighten the bleeder, and install it. I have some rubber plugs I use for the extension to the clutch line, friction-fit. Once the slave is bolted up, I remove the rubber plug for the stock rigid line, though you may have a SS flex line, I think, should be no-difference. Connect it. I usually leave the master cyl dry and just begin using the syringe to push fluid into the system from the slave bleeder. I use a teeny hose clamp to hold the tubing to the bleeder, and loosen the syringe so the tubing and bleeder can revolve either open or closed, depending on what I am trying to do w/it. Close the bleeder if you need to re-fill the syringe. Remove the syringe from the end of the tubing, and fill the syringe, and when you re-connect the filled syringe, if there are air bubbles in the tubing, a bit of 'pulling-out' pressure on the syringe stopper (the plunger) will allow the bubbles to move into the syringe body, and float to the top, leaving you w/a full body of fluid and no bubbles. Open the bleeder valve again, and continue to push fluid up the hydraulic system until you see the fluid start to accumulate in the master cylinder reservoir. This will usually be announced by a multitude of tiny "fizzy" bubbles in the fluid, just what you want, as the fluid is removing the air in the system!

Keep doing this until you don't see the "fizzy" bubbles any more, an indication that you have purged the air from the system. It may be necessary to remove some fluid from the master cyl reservoir if it fills, and you still have "fizzy" bubbles. At some point, you should have fluid and pretty-much no bubbles coming through the big & small holes in the floor of the master cyl. You should close the slave bleeder, and start to pump the lever, which should very-quickly show you to have some immediate resistance, and you should have the sense that the clutch slave is moving the pressure plate into disengagement. CAUTION! If you pull the lever w/the reservoir top off, and it has bled then you will get a geyser of fluid from the tiny front hole closest to the banjo bolt! If you carefully pull the clutch lever, you can see the geyser, and just don't pull it rapidly which will shoot the brake fluid everywhere. I usually cram a bunch of paper towels around the master cyl reservoir and replace them as required. You can always replace the cap which is probably the best way to do it, be careful how-much torque you use the tighten the screws. I usually have a bunch of replacement screws on-hand for the reservoir cap. A tapered flat-head Phillips screw or an allen-head will work, and I have used a hex-head machine screw in a pinch. If you have problems with the Phillips head screws, I cut a slot w/my trusty Dremel & a cut-off blade, and use a good-fitting slot head screwdriver.

Now you pump the lever to a point of pressure, and open the slave bleeder, as you would in a traditional bleeding, and feel the lever go to the handlebar-DO NOT RELEASE THE CLUTCH LEVER! Hold the lever to the handlebar, and tighten the slave bleeder. Now you can release the lever. Do this several times and every time you do, in the clear plastic tubing and the syringe still connected to the bleeder, you should see a solid column of brake fluid slightly-moving with your efforts. By now, you should have a firm clutch lever w/very-little free-play, and a total release of the clutch pressure plate. This concludes your work. Make sure you clean the brake fluid thoroughly. Discard the used brake fluid, never return it to the container!

That's how I do it, and I have pretty-much given-up on trying to rebuild master cyl's, I just buy a new one if the old one is bleeding internally.


http://www.vmaxforum.net/showthread.php?t=28499&highlight=reverse-bleed&page=4
 
I have to get some supplies to do the reverse method..
Thanks for the info..
 
Blax, you might be right.
I just got in from bleeding the line again.
This time, I led a clear tube from the bleed fitting, down to a catch jar. I let gravity bring it down, then pump assisted till dry.

Removed bleed screw to put a little grease around the thread to seal up any micro gaps that can let air into the suction line while bleeding. (read on the internet, that you can eliminate false air bubbles this way). Filled with fresh fluid. After gravity fed, pumped a little thru the system. Was looking good,, no air bubbles of any sort.

Locked down the bleeder tap and tested again.

It felt GREAT for about 10-15 seconds, then it felt like you took a pin to a soda can.
Pressure slowly released till the lever could be held with your finger tips.

Since there are no visible leaks anywhere, all I can think of, is that the rubber o-rings in the piston has degraded over the years. (rubber does this, over time anyways).

So now I'm looking at the Cylinder Repair kit, vs replacing the entire MC.

I still might pick up a repair kit if I get a replacement MC or not, since I would like newer seals.

MC Repair kit (clutch) 2KW-W0099-00-00

What condition is the MC you mentioned?

Thanks
 
Thanks Blax..
Since I'm on a budget, I'm going to try the Cylinder Repair kit to see if that resolves the issue..

Thanks again.
 

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