I know I use DOT 5 brake fluid in my system but the bike has sat for many years. I just got everything cleaned up so can I run DOT 3 through the brake system to check for leaks and flush debris I may have missed. Then fill w/ DOT 5? I know the 2 fluids can't be mixed, I just don't want to waste the DOT 5 if something is wrong. Thanks!

 

I would say do not run DOT 3 thru the system.

The seals etc within the master cylinder and caliper are not compatible with DOT 3. I do not know the details. Flush with DOT 5, then fill with DOT 5. And be sure it is not 5.1 or anything other than 5.

 

ok but man talk about $$$.... DOT 5 is not cheap.

Right now my bike is winning the battle.......I think I'm gonna sell it. My leg is killing me from jumpin' on it and it seams one thing after another. I'm goin' fishin'!!

 

i can bleed the whole system out with less than a small bottle about 9$ around here,what about dot 4? i have heard people talking about using it instead of dot 5 ?not sure about if the two will work together or not.

 

Stick with Mick on this. DOT 5 only. Seals are not compatible.

 

NOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!

DON"T DO IT!

I hope I've caught you in time. If there is one thing I have learned about ironheads, it's to NEVER, EVER, EVER, EVER: EVER! mix dot 3 and dot 5 brake fluids. They do not play well together. Mixing them will cause seals to turn into mush. You will suffer brake fluid leaks from HELL. You will ride with a wet, slippery, throttle hand for MONTHS even after you think you have finally fixed the leaks. You will have no front brakes. I'm speaking from experience here.

My recommendation: Stick with the dot 5. We aren't talking about an enormous amount of money savings here. If you properly rebuild and clean the master cylinder and the wheel cylinder, you shouldn't have any brake fluid leaks.

 

CarlGrover answered this question too, and brilliantly i might ad.

 

I didn't mix the two I was wise to wait for info. My knee is healing along with my shin so it'll be a day or so. One day it starts easy, the next day it beats my leg like a step-child. I've lost spark in one plug now so I'm gonna just buy new plugs. FM says gap is .060 but that is way bigger than the one's that were in there. I was getting better spark before I f**ked with it. "If it ain't broke don't fix it".........oh well tomorrow is another day.

 

The 060 is wrong. I have heard it was a marketing ploy by HD back then - supposed to make the new ignition system sound good or whatever.

The guideline is:
electronic ignition gap is .040
points ignition the gap is .030
mag ignition the gap is .020

 

To topic... DOT5 fluid is developed for 2 reasons:
1. higher boiling point = brakes don't fade on heavy braking
2. it doesn't absorb humid (=water) from air = no need to bleed of change fluid
Actually for military use, no service required...

DOT 3 and DOT 4, DOT 5.1 are glycol-ether based fluids
DOT 5 is silicon ( Demethyl polysiloxane) based fluid

DO NOT NEVER EVER MIX ANYTHING WITH DOT 5 !!!!!!!!!!!
DO NOT NEVER MIX DOT 5 AND DOT 5.1