Well after months of working to get my 86 XR600 ready to ride, I found that my front disc brake doesn't work. I installed a Baja Designs lighting kit to replace the lousy lighting the previous owner tried to make work and had the carboraters rebuilt so I wouldn't have any problems later down the road. My front brake was sticking so I replaced the caliper and I haven't been been able to get the brake to work. I'm thinking the master cylinder needs rebuilding because I can't get it to build pressure. I did have it empty for a couple of months so I'm sure the seals are bad now. Any thoughts?

If there are air bubbles in the system you won't build pressure, can be difficult to get them all out.  

There are some tricks that I'm sure someone will post about (I don't remember)

Do you know for sure that the caliper is ok?

I have a master cyl rebuild kit of that bike (if I haven't tossed it over the years) that I never used.

I bought a complete front brake setup off a 2000+ XR250 for $45 on ebay (4 or 5 years ago) and swapped the whole thing out. (didn't even have to bleed it!)  

All nice clean shiny "new" parts. ;)  PM me if you want the rebuild mc kit. 

Edited by MindBlower

I'm thinking the master cylinder needs rebuilding because I can't get it to build pressure.

Assuming you bled the brakes when you reassembled everything, it sounds right. Unless there's an obstruction in the line or air or both. If it was an obstruction you'd feel some resistance in the brake lever. If it's full of air or both it'd feel some degree of squishy. If it's the cylinder, it'd feel more like when you're bleeding the brakes (little to no resistance when squeezing the brake lever). Sorry, I don't know how much you know about brakes, so I'm just trying to cover everything.

I'd probably start by bleeding the brakes again.

 I'm pretty good with brakes as I've been a bodyman/painter my whole working career and have done brakes many times before. This feels like the master cylinder because you hear air front the master cylinder and no pressure buildup. I should just purchase a Mityvac for the brakes and I'm sure I'll use it in the future. Yeah I'd be interested in that rebuild kit if you can find it.

Well here's something interesting. I bought some wheels for a 1986 XR600 R as a backup for my 86 XR 600R that I just finished installing a Baja Designs street kit and got the top end rebuilt so I'm ready to roll! I took it out for a test ride and it's geared pretty low so I thought I would finally mount the Kenda DOT tires on the wheels and install them since it has a 42 tooth sprocket. Upon installing them I noticed that these are for the XR600L which is good because it's set up with the Kush type of hub (stock) but this set up is wider then mine, should I buy a L swing arm?

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