I recently got wiped off my '06 GS. The bike went down on it's right-hand side and among other things, the front brake fluid reservoir was smashed. By the time I got the bike back up, the front brakes were spongy to say the least.
I decided to flush and bleed the entire system while I was in there. I didn't know how, but my watchword has always been 'How hard can it be?'
A quick chat with a mate who's a techy at a BMW Motorrad dealer and 30 minutes' worth of digging on the internet yielded enough info to know what everything was, and how to proceed.
For anyone else interested in this job: don't be put off by the hype. It's not staggeringly difficult - just a bit tricky in places. If you have a reasonable amount of previous experience in bleeding brake systems, you'll have no problems.
The important points to remember are:
You have just tackled what is possibly the world's most needlessly over-complicated braking system.
I decided to flush and bleed the entire system while I was in there. I didn't know how, but my watchword has always been 'How hard can it be?'
A quick chat with a mate who's a techy at a BMW Motorrad dealer and 30 minutes' worth of digging on the internet yielded enough info to know what everything was, and how to proceed.
For anyone else interested in this job: don't be put off by the hype. It's not staggeringly difficult - just a bit tricky in places. If you have a reasonable amount of previous experience in bleeding brake systems, you'll have no problems.
The important points to remember are:
- The job is done in four parts: front wheel circuits, rear wheel circuit, front control circuit, rear control circuit. You can't just do the traditional 'front-brakes-'n-rear-brake' like you're normally used to.
- The fluid reservoirs for the wheel circuits live on the ABS regulator, under the fuel tank. You'll recognize them straight away - the fluid caps are removed using an 8mm Allen key.
- It is possible to fill these reservoirs using a syringe, but I don't recommend it. I built a fluid filler tool by gluing a soft tapered plastic plug to the end of a cheap plastic funnel.
- Keep a syringe handy for adjusting fluid levels. The bigger the syringe, the better, although a 10cc one will work fine in a pinch.
- Wheel circuits:
- Unscrew the Allen-head reservoir cap. The front is marked 'V' (Vorderrad, or 'Front wheel'), the rear 'H' (Hinterrad, or 'Rear wheel').
- Insert funnel, and make sure it's well-seated.
- Fill funnel about halfway with fresh DOT 4.
- Turn on the ignition.
- Press the brake lever, opening the bleed nipple at the same time. Flush until the fluid is clean and clear.
- Close the bleed nipple, letting go the brake lever at the same time.
- Bleed the wheel circuits in the following order: front left, front right (both through reservoir 'V'), rear (through reservoir 'H').
- Control circuits:
- No need to turn on the ignition for this round.
- Unscrew the handlebar (front) or under right butt cheek (rear) reservoir cap as appropriate.
- Draw off all old fluid in the reservoir and dispose of it. Refill the reservoir with fresh DOT 4.
- Locate the six bleed nipples on the ABS regulator. The order these must be bled in is not intuitive - if you're looking at the regulator from the left-hand side of the bike, with the fluid reservoir caps closest to you and the nipples in a horizontal line, mentally numbering the nipples from one to six, the bleed sequence should be as follows: 1, 2, 4, 1 (re-filling with fluid through the handlebar reservoir), then 6, 5, 3, 6 (re-filling with fluid through the under-butt reservoir).
- Press the brake lever, opening the relevant bleed nipple at the same time. Flush until the fluid is clean and clear.
- Close the bleed nipple, letting go the brake lever at the same time.
You have just tackled what is possibly the world's most needlessly over-complicated braking system.
