Front Brake Issue - '81 XJ650 Maxim

I noticed late last week that my front brake felt spongy and would barely work when squeezed. I opened the master cylinder and saw that it was low on brake fluid and what was left was pretty dirty. I decided to try bleeding the brakes and haven't been able to pull any fluid out of the bleeder screw. I've tried both the gravity method and vacuum with no luck.

I noticed that there also seems to be a leak under the master cylinder. I was thinking it might be time for a rebuild. The bleeder screw is also pretty old, so I am going to replace that as well.

Why won't the brakes bleed? I'm unable to build pressure with the brake lever either, just continues to feel spongy. Could it be a clogged bleeder? If I'm going to try and remove/rebuild the master cylinder, how can I remove it without bleeding the brakes first?

Any help would be great!

 

If your brake hoses are from the early 80's it is time to replace them . The hose. May be perfectly dry but can restrict inside . I highly recommend looking at top of the home page click xj4ever, Chacal has great stainless steel brake hoses as well as aftermarket rubber replacements as well . No these are not cheap ...BUT how much is your life worth??? I have the braided stainless brake hoses on both if my 82 Secas if you go with these your brake pressure will be so much better..

 

Thank you, I will look into new hoses. I'm not sure if they were replaced before I purchased the bike. Any insight on how I could bleed the brakes if fluid isn't coming out of the bleeder screw?

 

Remove the bleeder screw it can be plugged up .

 

If you can't build pressure at the master cylinder it probably needs to be rebuilt. If it is leaking then it may be sucking air into the system and pushing fluid out of the leaking area. I think I would start with the master cylinder/leak first. If that works I would then look at the hoses, etc. By the way, if you remove the bleeder valve completely can you get fluid to come out?

 

It tried loosening it and fluid did start coming out. Is it most likely clogged then? Would it be better to do a rebuild or buy a whole new master cylinder?

 

Sounds good, I tried loosening it and fluid did end up coming out around the screw. If I remove it completely, I assume all of the fluid in the lines will flow out?

 

Yes it will but it is a good thing to flush out old fluid anyway .

 

Sounds good, if I can't bleed it from the bleeder screw, is that the next best option to drain the lines?

 

Replace the bad bleeder valve with a new one and then try to bleed it. You will only lose a little if you have the new valve before removing the bad one.

 

I had the same problem on my 83 XJ650k. I think there may have been an air bubble right at the top by the master cylinder. With the bike on the center stand that is the high point. also since air is lighter than brake fluid it will all rise to the top. I had good results by reverse bleeding the brakes. Use a syringe to push the new fluid up through the bleeder valve to the top by loosening the banjo bolt at the master cylinder. Yes replace the lines if they are old. Mine were the originals the brake lines are the only part of your brakes that can fail catastrophically and leave you with no brakes.

It may also take a lot of working the brake lever back and forth to get the caliper to engage the disk if you have replaced the pads. Its not like a car, that is a tiny master cylinder and it does not push much fluid out with each squeeze. I thought something was wrong when I couldn't get any pressure on the lever. Finally out of desperation I just kept working it and all of a sudden I started feeling some resistance at the bottom and 30 seconds later it came up completely.

 

I agree with Witt. Reverse bleeding works great, but I also had to lightly depress the break lever a number of time to get the last few small bubbles out.

 

I use this, but remember to put a towel over the open master cylinder reservoir or you might spray fluid everywhere. Ask me how I know.

 

Rebuild the master cylinder, unblock the bleeder, rebuild the calliper, replace the lines (check the date on them if original yamaha).
All this needs doing, you can fit braided lines, but this can create a hard feel at the lever - it's a personal thing really.

 

I agree with the hard feel at the lever if stainless steel braided lines are used. I did and I prefer the softer feel of standard lines.

 

I ended up replacing the lines, and rebuilt the master cylinder and caliper. Everything works great now!

 

I noticed the change in feel switching to stainless steel from the stock lines - likely less "swelling" in the line itself. However, I also like the thought my bike will stop when no longer using 30 year old lines!