72 shovelhead brakes - Harley Davidson Forums: Harley Davidson Motorcycle Forum
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old 08-19-2012, 10:04 PM Thread Starter
Junior Member
 
Join Date: Aug 2012
Location: ohio
Posts: 3
72 shovelhead brakes

OK so I introduced myself and told my story in the new people section. I'm in the process of getting the braking back in order. And I replaced the rear master cylinder with one from SamsPowersports on Ebay. When I got it the instructions say that I must run dot5. But back in 72 they only ran dot 3. So the new lines and new drum cylinder I have are dot 3 compatible not dot 5. The guy from Sam's says just run dot5 but I did and the brand new (not rebuilt) drum cylinder is leaking out the boot. So I have to assume its because I'm trying to run dot5 through a cylinder that is made for dot3. So I have new springs, cylinder bolt, shoes, the drum is in spec and a new master cylinder. But that master cylinder is calling for dot5 and everything else is calling for dot3. What are your thoughts?
72HDShovelHead is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old 08-20-2012, 05:32 AM
Grandstanding Member
 
Dave63's Avatar
 
Join Date: Jun 2008
Location: PA
Posts: 29,803
DOT-5 can be run if there's NO natural rubber seals. I believe the seals in the slave in the rear drum are natural rubber.

I'd personally stick to DOT-3 or 4. You can get new cups for the rear brake slave at NAPA. Take the old ones out and the bore size should be printed on the cup, or take it with you and they'll match it up.

Make sure the bore isn't pitted too. If it can't be honed, then it's shot and needs repalcing.

__________________________________________
When the going gets weird, the weird turn professional.... ~ Hunter S. Thompson~

R.I.P. Rubberdown. 1971-2012
Dave63 is offline  
post #3 of 12 (permalink) Old 08-20-2012, 08:54 AM
EVO RULER
 
moose49's Avatar
 
Join Date: Mar 2011
Location: terra dei Limberlost
Posts: 3,721
Just did a 70 flh with a new master cyl it called for 5 but 3 causes no problems just rebuild your wheel cyl an use 3.

*CONFORMITY IS JUST A SLOW FORM OF SUICIDE*
******SUPPORT YOUR LOCAL INVADERS*******
********RIP RUBBERDOWN RIDE FREE********
moose49 is offline  
post #4 of 12 (permalink) Old 08-20-2012, 10:26 AM Thread Starter
Junior Member
 
Join Date: Aug 2012
Location: ohio
Posts: 3
I just installed new:
Springs
Shoes
Master cylinder
Drum cylinder (brand new not rebuilt)

Ok I'm going to flush everything and clean it up and start over with Dot 3 then. Thanks everyone!
72HDShovelHead is offline  
post #5 of 12 (permalink) Old 08-20-2012, 12:46 PM
Junior Member
 
Big Ed's Avatar
 
Join Date: Dec 2008
Location: central Penna
Posts: 9
My scooter all have rear shoes. I use DOT3. My understanding when you mix DOT5 in a cylinder that originally had DOT3 and wasn't theroughly cleaned, the mix of the two different brake fluids will deteriorate the seals.

1968 FLH assembled 6-21-1967
1969 FLH assembled 3-03-1969
1972 FX assembled 8-21-1971
Big Ed is offline  
post #6 of 12 (permalink) Old 08-21-2012, 06:09 PM
Banned
 
Join Date: Jun 2010
Location: Pennsylvania
Posts: 1,604
I rebuilt my '68s brakes with a new master cylinder, Russel braided rear line and DOT 5 about 10yrs ago and it hasn't leaked a drop. Drag Specialities has a DOT 5 rated master cylinders , and maybe even a rebuild kit for each. I'm thinking I only rebuild the wheel cylinder.

But IIRC , it only has to be new rubber pistons. It can't be ones that had DOT 3 and were cleaned. And flush the hard line on the frame with plenty of brake clean.
pb68slab is offline  
post #7 of 12 (permalink) Old 12-07-2012, 07:52 PM
Junior Member
 
Join Date: Oct 2012
Location: southern new jersey
Posts: 5
72 shovelhead brakes

i used the 5.1 fluid that is compatible with 3 or 4 but takes more heat because that master cylinder is right next to the front pipe ,try it.
hobo1948 is offline  
post #8 of 12 (permalink) Old 12-08-2012, 05:08 AM
Senior Member
 
Join Date: Jun 2012
Location: indiana
Posts: 341
check out ATE super blue raceing fluids. syn. they may come in DOT 5 on-line.
eagle1 is offline  
post #9 of 12 (permalink) Old 12-08-2012, 05:17 AM
Grandstanding Member
 
Dave63's Avatar
 
Join Date: Jun 2008
Location: PA
Posts: 29,803
Quote:
Originally Posted by hobo1948 View Post
i used the 5.1 fluid that is compatible with 3 or 4 but takes more heat because that master cylinder is right next to the front pipe ,try it.
Agreed. 5.1 is compatible witn 3-4, and performs better as well.

__________________________________________
When the going gets weird, the weird turn professional.... ~ Hunter S. Thompson~

R.I.P. Rubberdown. 1971-2012
Dave63 is offline  
post #10 of 12 (permalink) Old 12-08-2012, 06:41 AM
Retired citizen
 
SCHMIDTYS's Avatar
 
Join Date: Jun 2009
Location: Pt. Wash.,WI
Posts: 14,674
Is 5.1 compatible with 5 ???

Disclaimer : Don't believe anything I say unless you are absolutely sure that I know what I'm talking about .
SCHMIDTYS is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Harley Davidson Forums: Harley Davidson Motorcycle Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome