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Old Today, 01:36 AM   #1
Xoliul OP
Joined: May 2013
Oddometer: 27
BMW G650 X (brake) parts madness

I have an Xmoto with a really, really stubborn front brake that refuses to bleed properly and feels spongy after 6 attempts at it (using almost every trick imaginable).
I'm just going to rebuild it a bit, but finding parts is extremely hard.

I know all these parts are probably generic and shared, but it's nigh on impossible to find what is what exactly.

-I have a friend's Monster 620 standing next to it, and noticed the front brake caliper looks almost exactly the same. Seems to be a Brembo 6800 4-pot. The only difference I see online is often that it looks like this instead of this. The brembo text is smaller and has the logo above it. I suspect this is purely a visual update/difference, as the 6800 is used for both.
I want to confirm if buying this kit for Monster 620, would work?
-Is the front brake master cylinder the same as the F650? There seem to be differences. I want to know what kind of maintenance kit for the master cylinder I could buy?

Finally, not brake related, but I have a set of Zeta 'bend' handguards, seen here:
They never fit that well, they seem to have been made for handlebars with more pullback (not how the end parts are at a slight angle). Result is they drag against the grips and slow the throttle down when it returns...
Anybody can shed some light on if the pullback is standardized between bikes? Like I have no idea what will fit what. Even better if the straight one would fit, as these are way cheaper than barkbusters or SW-motech and look better and have more options
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Old Today, 02:16 AM   #2
old rider
Joined: May 2007
Location: Inman Valley South Australia
Oddometer: 802
got a replacement rear mastercylinder for my XC a brembo part for ducati for about 1/3 bmw price plus a brembo microswitch for the hand brake but can't help with the front brake.
My front break was really spongy - made sure the front master cylinder reservoir was dead horizontal then the reprom advises pulling the brake on moderately hard then let it off & repeat until air bubbles stop coming out. Took a while but worked like a charm, brake is the best it has been. Non ABS.
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Old Today, 02:24 AM   #3
Xoliul OP
Joined: May 2013
Oddometer: 27
Trust me, I've tried all of that and can still pull the lever into the bars without much effort. Me and 2 others have spent hours on it already, so spending 80 euro on parts isn't a big deal to me. I do want to avoid going to the bmw dealer since they are slow and expensive.

Some more research suggests it's a Brembo P4 30/34, shared with a lot of other bikes that should have seal kits available. Now I just wonder about the pump/master cylinder.
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Old Today, 04:36 AM   #4
The Jester
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Joined: Aug 2005
Location: Cornwall, UK
Oddometer: 826
I had a similar issue on an X-challenge - excessive brake lever travel - which I cured by replacing the brake lever.

On the X-challenge the lever is non-adjustable. The lever is made of alloy and has a socket where the steel pin from the master cylinder locates. Over time this socket wears leading to excessive lever travel as the pin springs out and this slack has to be taken up before the brakes start to work. It doesn't take much wear to transfer into quite a lot of travel at the end of the lever. I replaced the lever with a pattern part for a honda cb500 twin commuter bike which restored the normal brake travel and feel.

Not sure if the X-moto has the same master cylinder, but if the lever is non-adjustable I would try replacing that before going any further.
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Old Today, 05:00 AM   #5
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Joined: Mar 2009
Location: Wakefield, uk.
Oddometer: 21
Try putting a strap around the lever and handlebar and pulling the lever into the bar and leaving like that for a couple of days.
This will make any trapped air rise up the brake line into the master cylinder.

An old trick that still works.

Cheers Dave.
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Old Today, 05:11 AM   #6
Joined: Mar 2012
Location: Казань
Oddometer: 359
See photo, Xoliul already has adjustable levers...

Xoliul, I see your bike is non-ABS, so bleeding it should especially be non-problematic...
Have you got an inner hex bolt inside the master cylinder? If you do (if they exist on non-ABS) - you need to bleed that circuit too!!


Additionally, read this:

And an extremely interesting topic over on an Aprilia forum:


F-ing in Iceland and Faroe Islands, 2013.
--- --- --- --- --- --- --- --- --- --- ---
Detailed BMW X-Challenge build thread.
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Old Today, 05:32 AM   #7
Xoliul OP
Joined: May 2013
Oddometer: 27
Jester: I have one, had it for 2 years already. I tried switching between that and the old one (which wasn't worn either), not much difference, if any.
I could set my lever to max to make it impossible to pull into the handlebars, but that doesn't feel like the proper solution. I have 3 other bikes in my garage and they all encounter serious resistance before 1/3rd of the lever travel, this bike only gets that after 2/3s.

Coyotedave: I did that, multiple times: no change.
I even tried crazy stuff like using a big syringe to inject fluid from the bottom up to the top.

Bli55: that's actually the first thing I read I had not encountered yet. That mystery bleed screw might be there, I have no idea, will check tonight.
And yes I agree this bike should not be an issue, i've bled way more complex systems without issues before, hence why I'm a bit stumped.

If it's not that mystery screw, I suspect:
-small leakage at either bleed screw or copper washers
-Small leakage at caliper piston seals
-Master cylinder seals got tired and worn
-Braided hose has gotten a bit tired (unlikely but not expensive to replace)

Hence why I want to find proper replacements for those parts.
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Old Today, 06:35 AM   #8
Joined: Mar 2012
Location: Казань
Oddometer: 359
You should find very useful a Brembo yododyne(?) catalogue.
Google should know...

F-ing in Iceland and Faroe Islands, 2013.
--- --- --- --- --- --- --- --- --- --- ---
Detailed BMW X-Challenge build thread.
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Old Today, 07:49 AM   #9
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Joined: Mar 2013
Location: Central Albabamba
Oddometer: 237
Try re sealing your banjo fittings, heat the copper crush washers with a torch and let cool slowly to anneal them. This softens them up so they are ready to crush again. If your master is too small (moves smaller volume) it will be spongy, opposite is true for oversized master, it will lock up if you look at it Wrong. If all air is out and the system is matched I would suspect the lever. I thought my YZ brakes sucked until I adjusted the lever to provide proper engagement, now it makes me wipe out when it locks up. Guess there's a sweet spot there somewhere.
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Old Today, 03:11 PM   #10
Joined: Mar 2012
Oddometer: 82
Contrary to steel, copper softens when it is shock-cooled.

Find the little Hex, but be carefull, the brakefluid will squirt out.
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