84 FJ1100 bleed front brakes?

[jdvorchak]

I took the master cylinder and rebuilt it. Bench bled the MC and attached to the bike. The fluid in the brake lines was actually pretty clean but someone left the bleeders open so there is very little to no brake fluid in the calipers and anti-dive. I'm kinda stumped at this point. I tried to bleed the brakes as I would normally do. Staring with the furthest away (left side caliper) and not really building pressure although I'm getting some fluid out the bleeder.

My question is what is the proper sequence to bleed the front brakes with anti-dive still attached? I do have a Miti-Vac but rarely use it. I'm old school.

[Pat Conlon]

Your sequence is correct, start with the furthest.
I use my Mity Vac all the time, if you have it, why not?
If you have a large syringe you could try reverse bleeding. Just be careful about fluid coming out the reservoir.
DOT 3/4 does not play well with paint and plastics.

[jdvorchak]

thank you for confirming my sequence. Actually I use a combination of Mighty Vac and pump pump hold for the final bleed. Just never seem to get brakes bled with just the Vac. I'm probably not using it correctly.

[fjbiker84]

I've had to re-prime the lines two times since owning my 84 and all I can say is it is a dark art.  If the calipers are dry after rebuild, it is extremely difficult to get all the air out of them.  The second time this happened (the first time I gave up and rode the bike sans front brakes to a bike shop) I bought a brake bleeder kit and used that.  But even after pulling a bottle of brake fluid through the system there was no pressure at the brake lever.  I then tried a "trick" someone recommended on this forum - tie the brake lever fully compressed against the grip overnight - and it will correct itself.  The next day- at least partially - I had brake pressure.  It required the lever to be pulled almost all the way to the grip to fully compress.  I adjusted the brake lever screw to add more leverage and over time the system corrected itself fully and I had to let out the adjustment screw to release some leverage from the brake lever. This was the same situation I ran into the first time when the bike shop did their work.  I believe the problem is that the bleeder valve isn't positioned such that all the air can be expelled from the caliper. But you can get it to a point where they will work.  From there you have to use the brakes/wait till all the air in the system eventually finds its way out. As for the "trick" - I'm not convinced that the same thing would not have happened by allowing time to let air bubbles to work themselves out of the system.  Like I say, it's a dark art.

[Pat Conlon]

If you guys think the front brakes with the anti dive is hard to bleed, try bleeding the FJ with ABS lines.
Jeeze, that was a chore.

[CutterBill]

Tying back the brake or clutch lever and leaving it for any time does nothing.

There is a small hole in the bottom of the MC. When the piston is fully retracted, the reservoir is connected to the brake line thru the small hole. If the piston is advanced (lever squeezed) about 1/8-inch, the piston seal moves past this hole and completely blocks off the reservoir from the brake line. (If it didn't, then you would never build any pressure in the line; it would just go right back to the reservoir.) So there is no way that air in the lines can escape into the reservoir with the lever pulled.

What probably works is just the act of letting it sit overnight. The bubbles in the line worked their way to the top. You released the lever, the piston retracted and the bubbles escaped into the reservoir.  You could have accomplished the same thing by walking away and drinking a cold beer.
Bill

[jdvorchak]

Front brakes are bled and now onto the rear.
FYI I started with the left side Anti-dive then the left side caliper. Then right side AD and then caliper. I got tires of sucking fluid and air out last night so I used a large-ish rubber band to tie the lever back overnight. I've done that often over the years, I think the problem lies in that the VAc can't pull the fluid through fast enough to get all of the air in the lines. That is why some folks reverse bleed them with a large hypo. Probably just loosening the banjo bolt at the MC would work quicker for expelling the air in the lines. I have never tried that and quite frankly I'd be afraid to expose the brake fluid to air for that long if leaving it overnight,

The mighty-vac does a good job if all you are doing is the routine flushing or trying to bleed the caliper with the brake lines full of fluid. Starting with everything bone dry is a challenge to be sure.

So in summary? I did all 3 things. I bench bled the MC first. Then I tried to pump pump hold then onto the vacuum pump then tied the lever back for overnight. This morning a few pump pump hold and brakes are firm as they can be. I used the same sequence stated above starting furthest away and working my way back.

When I revive a barn find I don't even evaluate the brakes. Every thing comes off for cleaning/rebuild so I'm used to dealing with a dry system. It just takes a while. My OP asked for the recommended sequence and thank you for that.

FYI at least the rear brake system looks it came from a period Suzuki! One tip. If you don't have a rebuild kit, with internal O-rings, don't split the rear caliper.

[racerrad8]

Tying back the brake or clutch lever and leaving it for any time does nothing.

What probably works is just the act of letting it sit overnight. The bubbles in the line worked their way to the top. You released the lever, the piston retracted and the bubbles escaped into the reservoir.  You could have accomplished the same thing by walking away and drinking a cold beer.
Bill

Au contraire Bill,

For reasons I have not been able to determine, understand or figure out yet...

Tying the handle back against the bar even for a couple of hours does work and work very well.

There have been times we have bled a quart of fluid through a M/C and cannot get a perfectly solid handle. The first time I tried it out of speculation after reading it on this forum many times. I tied it back and went home, the next morning I cut the zip tie off not expecting any change. Much to my surprise it worked.

We now tie the handle bar and leave it for at least a few hours on all master cylinder bleeds. We do the basic bleed whether reverse syringe bleed, gravity bleed or pump bleed then we tie back the handle. Each and every time you untie the lever the lever is perfectly solid.

I know the holes in the motorcycle M/C are microscopic, especially when compared to automotive cylinders. I am not sure if the clamping allows all of the tiny bubbles to converge into one large bubble. Or if since the intake port is so small, the larger volume of fluid allowed in while compressed allows the fluid to flow properly through the compression chamber once untied...

I do not know why or how it works, but...

I do know it does work.

Randy - RPM

[red]

FWIW, you can replace the banjo bolt at the MC with a banjo bolt that has a brake bleeder built in. 
This little mod will be just the ticket for bleeding air from the highest part of the brake lines.

[jdvorchak]

FWIW, you can replace the banjo bolt at the MC with a banjo bolt that has a brake bleeder built in. 
This little mod will be just the ticket for bleeding air from the highest part of the brake lines.

Or do what I always do. Pump the MC a time or two and crack the bolt loose and watch for air bubbles. Usually only takes one or two iterations of that to free the air trapped in the banjo bolt. If there are no bubbles it will squirt fluid out pretty voraciously. Covering the bike with plastic and towels keeps the painted surfaces unscathed.

[jdvorchak]

Tying back the brake or clutch lever and leaving it for any time does nothing.

What probably works is just the act of letting it sit overnight. The bubbles in the line worked their way to the top. You released the lever, the piston retracted and the bubbles escaped into the reservoir.  You could have accomplished the same thing by walking away and drinking a cold beer.
Bill

Au contraire Bill,

For reasons I have not been able to determine, understand or figure out yet...

Tying the handle back against the bar even for a couple of hours does work and work very well.

There have been times we have bled a quart of fluid through a M/C and cannot get a perfectly solid handle. The first time I tried it out of speculation after reading it on this forum many times. I tied it back and went home, the next morning I cut the zip tie off not expecting any change. Much to my surprise it worked.

We now tie the handle bar and leave it for at least a few hours on all master cylinder bleeds. We do the basic bleed whether reverse syringe bleed, gravity bleed or pump bleed then we tie back the handle. Each and every time you untie the lever the lever is perfectly solid.

I know the holes in the motorcycle M/C are microscopic, especially when compared to automotive cylinders. I am not sure if the clamping allows all of the tiny bubbles to converge into one large bubble. Or if since the intake port is so small, the larger volume of fluid allowed in while compressed allows the fluid to flow properly through the compression chamber once untied...

I do not know why or how it works, but...

I do know it does work.

Randy - RPM

As I mentioned earlier. I think the vacuum bleeder won't pull fluid through quick enough to get any air trapped in the TEE fitting or higher up in the line. Tying the lever back opens the MC for flow in both directions so the air will eventually work it's way up through the fluid and out into the air gap above the fluid level in the reservoir. If you have clear tubing on your vacuum bleeder you will notice that the air bubbles actually move pretty slowly in the fluid.

Like you, Randy, I always tie the lever back for a few hours or overnight even when I think I have a good bleed. I am new to this forum but not new to forums or wrenching on motorcycles. I've revived almost 30 of my own bikes and I don't know how many customers bikes over the years. If there were an easier way to bleed a dry system, I'd know about it....LOL

[FJ_Hooligan]

For the sake of scientific research, the next time someone decides to "tie the lever back and wait overnight," please skip the "tie the lever back" part and just leave it overnight and see if you get the same results.

I'm betting the outcome will be the same.

DavidR.

[racerrad8]

For the sake of scientific research, the next time someone decides to "tie the lever back and wait overnight," please skip the "tie the lever back" part and just leave it overnight and see if you get the same results.

I'm betting the outcome will be the same.

DavidR.

BTDT...

That is why I finally tried the tie back method after being unable to get I solid lever.

Now, I do it each and every time with great success.

Randy - RPM

[FJ_Hooligan]

What?  No video?

Just kidding Randy. 

I'll have to believe you since I've never had to do this.  I've bled ABS and non ABS brakes, and clutch systems without even using a MitiVac.  I've had good success with just taking my time and letting the bubbles rise up to the master cylinder.

DavidR.

[racerrad8]

What?  No video?

DavidR.

That is not a bad idea. I can show the lever pulling all the way back to the grip. Let it sit over night, then cut the ties and the next pull does not go to the grip.

I will have to remember to do that on the next one we bleed.

Randy - RPM