Im not sure if this question has been asked before or perhaps even I may have a long time ago. Age makes one forget but just why is there a need to change brake fluid in bikes ever couple years or so? I have a 2003 road King classic that is now 16 years old. I think the fluid was changed once in that time. It always stopped prior and since. The first change was three years ago and the only reason was that some one on here said we should. Cars and trucks don't need it done, There are cars on the road that are40 and 50 years old. How many of you change the fluid in your personal car every two years? I would think a handful if that. Is the brake system on a motorcycle so poor that one has to maintain it like that? Like I said this has most likely been answered here before and I apologize for not finding it.

randy

 

Google is your friend, friend!

https://www.google.co.uk/search?q=wh...ge+brake+fluid

 

DOT 5 is very forgiving. Does not absorb water. However water can possibly get in and settle to lowest point.

Just don't pump it out with master. When old, it will bottom in an area that is surely corroded. Destroying master

Just dip it. Refill and use a hand vacuum pump to pull it thru caliper. Do not rush. Too much vacuum can easly pull by seal in master since it excerts tremendous pressure one way yet easly lets air in the other if you pull too hard.

 

I learned to bleed brakes with my Dad on the family car back in the 1950s, along with the clutch. Brake fluids back then were not as good as modern ones, but they still deteriorate, not least by absorbing water from the atmosphere. When you next bleed your brakes simply compare the appearance of the old fluid with the new stuff, and the feel and performance of your 'new' brakes!

 

Lots of folk "get away" with not changing brake fluid, but the system will work better and last longer with fluid changes. Not really much different than an automatic transmission in that regard. Most ignore it and replace the vehicle before the transmission fails. But, change that fluid every ~100k, and the transmission likely will never fail. Doesn't matter if you replace vehicles frequently, but if you like to go a zillion miles on one, preventative maintenance helps.

Anyhow, the Dot 3/4 brake fluid absorbs water, lowering the boiling which can cause the brakes to fail prematurely under hard use. Water in the fluid also causes rust and corrosion to the metal inside. Brake fluid also tends to goo when ignored long enough, creating interesting blockages and such in things like proportioning valves. For Dot 3/4, regular fluid changes are pretty important to good working brakes.

Your 2003 should have Dot 5 silicone fluid in it. That doesn't absorb water, but water does get driven in past seals, and then sits there as a water bubble. Silicone brake fluid (which Dot 5 is) was created for the military for long term storage. As such, it's more tolerant of being ignored and neglected.

 

Good answers thankyou, so rather than paying the local dealer to do it and the fact that its winter up here, does Hd sell a pump or kit that will evacuate the system so I can replace it all my self? Up here its going to cost me well over $150 to have them do it.

Randy

 

Get a hand vacuum pump. Not sure where up here is but Amazon is always your friend.

$22 . Search auto test vacuum pump.

I made the part you still need by drilling two holes in a Mason jar lid. One vacuum hose goes in 1/4 inch . The other goes to the bottom to act as a bubbler. Attach vacuum to hose in 1/4 ". The one at bottom to the bleeder on the caliper. Just pull about 5-8 lbs. Don't pull master too low.

 

~$45 per caliper for MoCo rebuild seal kits and gaskets, ~$40 for the front master cylinder rebuild kit and gaskets, ~$75 for the rear master, $25 for two quarts of DOT 5, and a nice quiet day to get 'er done.

 

Mity Vac, you can beat this price, however.
https://www.harborfreight.com/mityva...ump-39522.html

 

I have used them before, and I have one in my tool box, but I always get frustrated using those vacuum pumps. I have never had any issues by doing it old school, bleeding the master, then the line, and finally the calipers...by hand. A little messy if you are not careful, but no more messy than vacuum pumps can get and it works for me every time.