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Old 03-15-2005, 09:58 AM   #1
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Hyd. clutch info/adjustment

If you're driving a girly car, chances are you have a hydraulic clutch system. They offer some advantages, such being able to run a much heavier clutch since the fluid is doing all the work. Or for people who don't want a heavy pedal. The flip side of that is the clutch pedal usually feels so damn light you can't feel what's going on. If you're having problems such as low clutch engagement, soft/sticking clutch, it might be time to bleed the system. Or your clutch needs to be adjusted. Or it's time to rebuild/replace the master, and it's probably a good idea to rebuild/replace the slave as well.

If your clutch engages too low, this could present problems. This might result in early wear of synchros, gears, clutch & flywheel. If it engages too high you will stress the master/slave cylinder seals, once the clutch is all the way down and the clutch fork has nowhere to go. It creates higher pressure which the system can temp. handle, but too much over time will cause the seals to blow.

Hyd. systems work by when the clutch is depressed, it moves a lever that is attached to an adjustment rod. This rod pushes in a piston that sits inside the master cyl. Once this piston is pushed in, it puts pressure in the fluid line, which travels to the slave cyl., which then pushes on the clutch fork and then disengages the clutch.

To bleed the system, first find the slave cyl. attached to the bellhousing. If nothing else, just follow the clutch line until you do find it. There is bleeder valve (see attached pic 1) on this slave and bleeding the system works in the same way as your brakes. Have a friend pump the clutch and hold it to the floor, and then open the valve to let it run out. Ideally you should have a hose attached on the end to keep air from running back in, but I don't and it's usually fine.

Periodically the system should be fully bled and replaced with new fluid, as brake fluid might begin to trap moisture and cause the clutch to be spongy.

To adjust the clutch to engage earlier, loosen the lock nut and turn the rod into the master. Turning it away will cause the clutch to engage later. Again, the ideal setup is the clutch is finished engaging 50% out, and is 100% engaged about ~13% of the travel. You don't want the clutch engaging right at the floor, but a bit off. Turn it 1/2-1 turn and then drive, every small change should make a noticeable difference.

To replace the master (or slave), remove the clutch line, then unbolt the cylinder from the firewall. It is much harder to get the cotter pin off the clutch lever when you can't wiggle it away from stuff. Once it's unbolt from the firewall, crawl under the dash and remove the cotter pin, and then the key. Rebuild kits usually involve replacing the main spring, seal, and piston.

I know not many ppl have hyd. clutch systems on here, but I thought I'd do a write-up anyway.
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08 cbr 1000
73 mach 1
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