I bought a used motorcycle a few months back and it now needs some fluid. The fluid is yellow-ish brown so it needs to be bled. Problem: Manual says it uses DOT 4, previous owner thinks he put in DOT 5. I've heard mixing the two can cause some serious sludge problems. How can I bleed the system if I don't know what type is currently in the bike?
All good answers, sofar, except for draining it dry. You cpould, but you don't want air in the sysytem either. Flush the new fluid through until you are certain all the old is out.
Just use the recommended type and pump it through till only new, clean fluid comes out. You'll get a lot less mixing if you can suck all the old fluid out of the reservoir and refill it with new before you start bleeding.
Always give year, make, engine size and model # when asking questions. We need all of that info to give an informed answer. If the manual says to use DOT 4 - use DOT 4. Usually the fluid type is written on the master cylinder cap. Keep bleeding the system until the color of the new fluid comes out.
Brakes are far to important to mess with. Bleed them out and replace the fluid with DOT 4 like the manual says. It is better to spend a couple extra bucks for fluid than the thousands you will spend if you fail to stop. If it was DOT 5 it is silicon based and will not react well with DOT 4. If it was DOT 5.1 it will interact fine with DOT 4. To bleed it out open the bleeder valve and pump the brakes while catching the old fluid and adding new DOT 4. If you want to go a little faster take a syringe and suck out the reservoir fluid first then add the new and start pumping until the new fluid come out the bleeder.
As stated, drain it dry and start fresh with recommended fluid. Make sure you clean the master cylinder out good and make sure the tiny reverse pressure hole is clear. To bleed, I suggetst a one-man bleeder setup...can be purchased for <$10 at an auto parts store. Or, if you have extra cash, you can get a mity-vac brake bleeder. Make sure to keep checking the fluid level in the master, don't let it go dry. After bleeding until no air bubbles come out, pull the brake lever in and tie it with zip tie or shoe string and let it set overnight...any remaining air will rise up and out the reverse pressure hole.
