Replacing brake fluid

With everyone in COVID-19 lockdown it seems to be the right moment to give the mistress in the garage some loving tender care. Todays task was to replace the brake fluid which I haven't done a single time just yet. The brakes were starting to feel a bit spongy so thought it would be a good time to sort the problem out. First of all we need some tools i.e. an 11mm wrench, an 8mm hex socket, a 6mm allen key and a torx  VT20. In addition a rag, a 30cm hose and a small disposable bottle will come in handy to make the process less messy.

Secondly we need some new brake fluid. The bike can can use either DOT 4 or DOT 5.1. The latter has a higher boiling temperature so I reckon it is better in hot climate with many hills like Hong Kong. In addition it is handy with some degreasing cleaning spray. All fluids are available at Moto Mart up in Kowloon.

Start by attaching a 30cm plastic hose to the front bleed nipple and put the other end in a small bottle. 

Remove the lid from the master cylinder and tie a rag around it to prevent spills. An old sturgis T-shirt is here doing the job.

Using the 11mm wrench losen up the nipple by turning it 1/4 of a turn while pumping on the brake handle to force the old fluid out of the system. About 25 times will almost empty the master cylinder. When it is almost empty stop and clean out the inside with a rag. Mine had a lot of old crap at the bottom.

Here it comes in handy to have the cleaning spray but make sure it is all dried up in the end. When it is nice and clean fill up the system with new fresh fluid. Pump 3 full master cylinders through the brake lines to properly flush out the old liquid.

Time to do the rear one and start by removing the rally tank and you find the rear brake fluid tank hiding behind. Remove cap and gasket.

Attach the hose to the rear nipple in the same way as on the front.

Open the valve using the wrench and pump on the rear brake until the rear brake fluid tank is almost empty. Repeat 3 times to flush the system.

Fill the rear tank up to the maximum level, put the gasket and lid back on and put the tank back on the bike. Finish by leaving the bike front brake zip tied in to put pressure on the system to force any air out. 


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