Master cylinder cover

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9/6/2018 7:51 PM
Edited Date/Time: 9/6/2018 7:52 PM

One thing Ive never been able to understand is the carbon fiber master cylinder covers. How does denting a master cylinder make it stop working? This even happened to Eli before or they said that was what happened. But how would a dent actually stop the fluid from flowing? . Ive read the descriptions of these parts and it just says protects master cylinder from becoming useless from damage. Can someone please explain how a dent on a master cylinder would cause it to stop working. Thanks.


9/6/2018 7:56 PM
Edited Date/Time: 9/6/2018 7:57 PM

If you get a dent big enough where the piston is and it does not allow the piston to release This will hold the pressure in the line and cause the brake to lock up. This is my understanding of what happened to Eli and is pretty crazy, been riding for 30 years and have never witnessed that happen.


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9/6/2018 10:10 PM
Edited Date/Time: 9/6/2018 10:14 PM

Ok that makes sense. That would have to be a pretty big rock going very fast to dent it to the point where it bocked the piston. I keep seeing these when looking at the factory bikes and couldnt find any info on what they actually do so I appreciate it. I have never even seen or heard of even a small dent or even a chip in the cyinder so this is pretty crazy but apparently it can happen. So I take it after that happened to eli is when everybody else got these covers? Because he obviously did not have it at the time and I dont see factory kawi skimping out on any protection the other brands have.


9/7/2018 2:14 PM

In theory you could "crack" the master cylinder when it gets hit and the fluid leaks out. Not sure what material is being used for the master cylinder but Aluminum likes to crack and shear, steal likes to bend. IIRC Magnesium likes to crack as well.

I'd be more worried about the line connector being hit at the body of master cylinder and breaking before the actual master cylinder itself.

But I trail ride so what do I know, we just put protection on our bikes so we can run into trees wink


9/7/2018 2:22 PM

Yeah, if the master cylinder bore is damaged the seal will either leak and you lose your brakes, or you can prevent the piston from extending and bleeding back to the master. That will lock the brake full on once the fluid expands.

I've also had banjo bolts come loose from being hit with a rock. Sounds crazy, but it is possible.


9/7/2018 3:03 PM
Edited Date/Time: 9/7/2018 3:04 PM

The actual master “cylinder” is what’s the most critical component that they’re wanting to protect. The cylinder is just the “tube-like” feature at the bottom of the reservoir. But, since we were designing a new part for the teams, we asked the managers, tech’s & mechanics “what do you really want protected?”

And we came up with:
(There’s a guard on both masters in picture above)Photo


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9/7/2018 7:09 PM

Nowhere near as trick as the carbon fiber unit but probably just as effective! Devol Racing, circa 1997