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Lost hydraulic clutch fluid

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This is my brother's bike. His clutch felt like it wasn't engaging quite right a week ago, then it got better. However this weekend the clutch completely went out. That is, the lever got really soft and the clutch would not engage. Popped open the reservoir cover and there was no fluid.

This is a brand new bike (07 450xc), so Im a little surprised. Could it be that the clutch wore out somewhat and the plunger needs to engage "deeper", thus needing more fluid. Or is there a leak somewhere? No visible leak on the outside was found. Could there be a leak inside the motor?

I added more fluid (mineral oil) but it's still dead. Air in the system?

Any input greatly appreciated

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The RFS brakes and clutch use a TINY little reservoir, and when the level drops a little through normal system wear or seepage, there goes your brake or clutch. This is the reason most street legal bikes (except the new 07 EXC!) use external clear reservoirs. Without a visual way to check the level, you MUST remove the clutch cover often to check the level. (The brake reservoirs have windows.) How often depends on your own paranoia and how hard you abuse the clutch.

If you spend an afternoon slipping the clutch in a mud bog, you can bet you lost some friction material and the level will be down.

I now carry a tiny (2 fl oz) plastic bottle of mineral oil in the woods, so I don't have to ride out clutchless again. If you catch it right away, before the air gets down into the hose, you can just top up the reservoir and pump the handle a bunch of times. You can see the air bubbles seeping up and soon you "may" have your clutch working, at least most of the way.

To bleed it right you need a big syringe and tubing so you can back bleed from the slave cylinder. Magura makes a bleed kit - buy one and be happy.

I sure wish someone would market an oversized clutch reservoir with clear window. I would buy one tomorrow.

John Davies

Spokane WA

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My bike did the same thing after the second ride and left me hanging. I do not think the line is bled very well at the factory. I drained the mineral crap out and put in ATF fluid and bled it through and it has been problem free.

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