T-3 brakes won't hold

[tecate kid]

My 84 T-3 won't hold prime in the rear brakes. I can get them to bleed with what I can tell is all the air is out of them, but as soon as I get on it and ride they go soft. They will have air in the system again. Is there a trick to get the mto bleed decent? I am starting to think the master cylinder is bad, but I don't have any leaks, and it seems like it does work good once its bled. Any help is appreciated.
tecate kid

[gizmo_22]

try the caliper seals... had the same problem on a truck... make sure the bores and seals are in good condition or even replace them... cheaper then a master cylinder...
also crack somewhere in the seals?

[InPiEcEs]

I used a vacuum beeder on mine.
It was way quicker than the old pump,pump, pump method.
Get em at most parts stores.
I hooked it up to the bleeder, filled the brake reservoir, and put some vacuum to the bleeder, then cracked it open.
You have to pay attention to your fluid level while doing it, while keeping vacuum on the bleeder..
It will pull fluid down the line to the caliper, and get a lot of air out. Then you finish up the old way to get rid of the remaining air.

[tecate kid]

Well I've bled them a couple time now, and I usally have all the air out when the bleeder gets cracked. Just seems like they lose prime. Could the oil be leaking past the top cup on the piston? It did some "custom" o-ring installing to help keep it out against the cylinder wall, but not usre if it helped. If the caliper was leaking I should see some oil on my brake pads, but they are always dry, same as the bottom of the master. Has a little dampness but thats just from the lower o-ring. Does anyone know if a master from another machine will work? Even with some mods to make it fit?
Thanks guys,
tecate kid

[DixiePlowboy]

Mine's got a rear master cylinder off a 300ex, but it requires a bracket to be made because the feed inlet would hit the frame otherwise. It feeds from the front instead of the rear like the original does.

You'll also have to cut out a small slot in the bracket and use a couple nuts for spacers at the m/s to bracket for the Honda part to sit flush on the bracket.

[ColeTrickle]

I have seen piston seals get little tears in them that will cause the master to lose its prime. When this happens no fluid seems to get by but it doesn't build up pressure. Also bore may be damaged inside. Easy enough to pull the piston assembly out and check it out.

[scooterroo]

your checking your fliud level after your bleeding them right? change out the seals on the caliper, if that dont work, your master might be in need of new seals as well. you can fabricate a bracket yourself to make just about any master work. thats the beauty of the 84/85, they needed a bracket to hold on the master, get yourself some 1/4" thick aluminum, availible at any lowes or home depot, measure up your holes and make up your bracket. waalaa, worked for me.

[tecate kid]

Thats what I'm gonna do if this don't work. I think the inner bore is trashed from one of the previous owners running it without the feed tube on, and getting it full of water/mud. A freind has some old stret bikes that he said he will sell parts off of. So I may be making a trip to his place this weekend. Oh well, It might as well be a little more "hybrid". You guys have any pics of your setups?
tecate kid

[BigGreenMachine]

I scored a NOS master for like 49 bux a few months ago. Its for a KXF Tecate but it will work. Haven't ran it yet.

Running a good rear caliper and a good working master on mine. No problem to brakeslide on pavement with light pressure. Running DOT5 fluid.

[tecate kid]

So I must have something wrong with mine, Once they are pumped up they still will go to the peg if I step on them hard. Guess I will have to see if they work today. I was thinking of running hydralic fluid or ATF in it instead of DOT3 fluid. Would this cause any problems? I don't ride hard or for very long so heat isn't really a problem. Any thoughts on this?
tecate kid