Soft rear brake - '83 venture royal

[rhanzlik]

I have an 83 venture royal the I have been ridding since '84. Last year I have a local shop rebuild the front forks with new seals. In the process, they were to bleed the rear brakes. I'm pretty sure they didn't have a clue as to how to bleed the unified brake system. When I got the bike back (finally), they said they bled the rear brakes but they couldn't get then to stiffen up. they said I had to pump the rear brake in order to get the pressure up. I have been told that this type of braking system require some special handling in order to get all the air out. It looks like I'm going to have to do it myself to get it right. I don't think there is a bleeder valve under the cowling on this bike and it has never had the extension tube modification done that I know of. I am the second owner of the bike and the first owner only had 6000 miles on it when I bought it.

 

Can someone please tell me how to bleed the rear brakes on this bike and how to do it properly? is there some sort of magic method I should use in order to get it right? I would like to sell the bike but I can't really do that with the brakes like they are.

 

 

[gaj1917]

It's not a huge job, assuming you know the basics bleeding brakes. Keep in mind that the foot brake pedal actually activates the rear plus the front left brakes. Start the bleeding process at the front left - it's the greatest distance from the pedal slave cylinder. Bleed the anti-dive as well. You'll need someone to pump the brake pedal, and hold, while you work the bleed screw. Then proceed to the rear brake and bleed that. If rear braking is still soft after getting all air out, it's likely your slave cylinder needs attention, or the brake hoses have become so soft with age that they are expanding under pressure.

[bongobobny]

A better way to bleed the brakes is to install a device called a Speed Bleeder instead of the regular bleeder for each caliper, and use a vacuum pump to bleed the brakes. Using both a vacuum pump and speed bleeders makes it a VERY efficient one man job, and you do not have to press the brake pedal at all, just make sure the master cylinder does not go dry; keep adding brake fluid during the process. Yes, follow the procedure GAJ mentioned by starting with the left front at the anti dive. With the speed bleeders the size you need is 8mm x 1.25 (thread pitch). For the front, you will go through a LOT of brake fluid, it is a looong way from the rear master all the way up to the front!!

 

What GAF says about the brake lines is very true, chances are they were never replaced so you are dealing with 34 year old rubber!! And yes, it sounds like the dealer you went to does not know what they are doing!! How were the brakes BEFORE they worked on them???

[Prairiehammer]

Here is the Technical Bulletin concerning bleeding MKI brakes. Note it is the highest point in the system that should be bled first, not the most distant from the master cylinder.

M85-016 Hydraulic System Bleeding Methods .pdf

[gaj1917]

A better way to bleed the brakes is to install a device called a Speed Bleeder instead of the regular bleeder for each caliper, and use a vacuum pump to bleed the brakes. Using both a vacuum pump and speed bleeders makes it a VERY efficient one man job, and you do not have to press the brake pedal at all, just make sure the master cylinder does not go dry; keep adding brake fluid during the process. Yes, follow the procedure GAJ mentioned by starting with the left front at the anti dive. With the speed bleeders the size you need is 8mm x 1.25 (thread pitch). For the front, you will go through a LOT of brake fluid, it is a looong way from the rear master all the way up to the front!!

Hope I don't hijack the thread here - but interested to know what brand of vac you're using. I have a MityVac, but have found it very difficult to get a good seal at the bleed screw.

[gaj1917]

Here is the Technical Bulletin concerning bleeding MKI brakes. Note it is the highest point in the system that should be bled first, not the most distant from the master cylinder.

[ATTACH=CONFIG]107117[/ATTACH]

 

Correct, and have read comments about bleeding up at the front master as well, but I've never found it necessary to bleed there or at that metering valve, fortunately, as the valve is a bear to access. Even when I replaced my brake lines with stainless steel, classic bleeding at front and rear was all that was necessary. Whatever gets you on the road I guess.

[utadventure]

Find a time and come over. I'll give you a hand and get to know you!

 

Dave

Taylorsville

[bongobobny]

Dave, I was sort of HOPING you would notice this thread and offer to help, I know you know what you are doing!!

 

GAJ, I use the mity vac too, can't remember if I used the black rubber adapter, or if I used a tight fitting clear hose adapted to fit the line...

 

Prarriehammer, I forgot all about that TB! When I did my 1st gen I had already converted to the MK2 system with the bleeder up by the neck when I switched to SS lines. Bought the complete MK2 kit from buckeye and switched to MK2 forks and front and rear calipers. That was my first modification I did with my '84 as I felt the whole brake system was anemic to say the least!! Good pedal/handgrip but lacking in stopping power...