1971 FLH brake fluid.

[10scDust]

I have a 1971 FLH mostly stock with drum brakes.

Recently I replaced the rear brake master cylinder. I found some old specification information that tells me this:

"Recommended Fluids
Harley-Davidson recommends 4 quarts of SAE 50 or 60 engine oil in all 1966 through 1984 shovelheads. The transmission uses 1.5 pints of HD transmission lubricant, although many people use 75w90 gear oil mixed 3-to-1 with Lucas oil. Harley-Davidson makes two types of fork oil for shovelheads. HD Hydra-Glide fork oil is for 1966 to 1969 models. All shovelhead models 1970 and later use HD Type B fork oil. HD Primary Chaincase oil is used in the primary chaincase. Shovelhead models from 1966 to 1975 use Dot 3 brake fluid. Models 1975 and later use Dot 5 brake fluid."

Should I use DOT 3?
Or, should I use DOT 5?

Either way I will bleed out the old fluid before I am finished.

One experience I had, in my much younger days, I put DOT 3 in a 1991 FLH rear master cylinder, it eventually locked up the caliper and nearly caught on fire. I was naive & a DA...
I am leaning towards stock recommendation, although the filler cap is stamped to use DOT 5.

I need to know if DOT 5 will hurt anything if I go that way.
TIA

[JBinNC]

My preference for H-Ds is Dot 5, because it will not harm paint, and is not as hydroscopic and so system corrosion is reduced. If you do switch, you need to rebuild the wheel cylinder and flush the line with Dot 5. Any mixing of the two types of fluid causes problems, as you already found out.

Jim

[rockman96]

DOT3 and DOT5 are NOT compatible. If it has not already been converted (which it probably has not), I would stay with DOT3. If you were going to replace the entire brake system for whatever reason, I would then switch to DOT5 for sure.

[confab]

Beware of the chain supply stores when you're doing brake fluid.

I picked up some "Dot 5.1" thinking it was the same thing. But it says in small print that is it not compatible with Dot 5.

I still have no idea what it is or why anyone uses it? But you're not supposed to use it with DOT 5!

[confab]

PS: Oreilly keeps DOT 5 in stock.. (Here, anyway)

[Guest]

if ya strip down & clean the master cylinder & the caliper parts with isopropyl alcohol,
then pump some through the hoses & dry the lot with an air line,
then rebuild with new seals & you can use whatever fluid you want,
********DONT just 'Pump It Through' when bleeding, you gotta do it right,**************
I cant advise it, but I have on one or two occasions cleaned everything out with a wash in Alcohol, & then used the old seals as they were fairly new anyway & never had a problem, cleaning properly is the trick.

[rockman96]

I cant advise it, but I have on one or two occasions cleaned everything out with a wash in Alcohol, & then used the old seals as they were fairly new anyway & never had a problem, cleaning properly is the trick.

If you are dealing with a bike old enough to have DOT 3 in it, shits gonna need replacing anyway... Yes, it can be done, but cleaning it isn't the best route. Replace it. Brakes and tires are two things I won't fuck around and go cheap on.

[Guest]

It looks like you need to stay with DOT3

[10scDust]

Thanks for all the advice and recommendations.
ChopCult rocks!

What I am thinking about doing, and that is, rebuilding the rear cylinder, or replacing it if I deem it needed. (I have that experience)
Replace the solid line section, of which someone once used copper tubing, I know the CUP pressure rating is not high enough for hydraulic brake systems, and they may already have DOT 5 in there.

Like Rockman said: "Brakes and tires are two things I won't fuck around and go cheap on."
Once I get it back together DOT 5 will be the fluid used, as JBinNC said: "My preference for H-Ds is Dot 5, because it will not harm paint, and is not as hydroscopic and so system corrosion is reduced."

I'm only dreading the task because I'm dealing with the stock axle and drum brake configuration, add to that there is an HD side hack on it, and it won't go through the double doors into my a/c'd shop room in the back. Which translates to laying on cardboard using a floor jack and blocks and dealing with the heat & humidity vs a/c and lift mechanism. But I'll get her done! She's a good old running baby and deserves it!

[Guest]

is the sidecar not easily removed so you can get the bike inside ?
can you put up pics of the sidecar mounts, i'm thinking of fitting one due to bad Hips & could do with some phot help to see whats involved in fitting them.

[JBinNC]

FYI,

There is a bronze tubing available and approved for use as brake tubing. I have used it (on cars) and it is easy to form and bend, making it convenient to use, and it does not rust like the steel tubings.

Jim