My front brake lever pressure has been very inconsistent lately. Sometimes the brakes apply without giving the lever much of a squeeze, then other times you have to squeeze it almost the whole way in and they still feel weak. My brake fluid could stand to be changed, but there is plenty in the reservoir. I haven't had the reservoir open lately, so I don't think it needs bleeded, unless that is just something that needs done in general every now and then. I have limited knowledge in brake repair, especially disc brakes, so any suggestions are welcome!

Thanks!

I would change your brake fluid and then thoroughly bleed the system. DOT 3 & 4 fluids will absorb moisture. When your brake grabs quickly, does holding the lever cause it to slowly pull in more? That is air in the line.

No, it's more like an off or on kind of thing. When they are working, they grab like normal and you can't collapse the lever. But when it is acting up, yes, the lever just seems to get spongey and the brakes weaken to where you have to really hold the lever in to get it to stop effectively.

I'm with Glen - try the fluid first. Intermittent loss is normally a master cylinder issue tho, unless you're boiling it - which I cant see.

After knocking loose my banjo bolt today - I had a similar experience. You may want to check your fittings - hopefully something simple

Which is the banjo bolt again? I've heard of that...

I took the bike for a nice ride the other day. The brakes seemed fine for the first 30 minutes, but then after getting up into the trails, I noticed the spongy feeling return. Then for the rest of the street ride home, it was still spongy. I haven't changed the fluid yet (it is still nearly full though), but will do so very soon...

The banjo bolt is the bolt that holds the brake hose onto the master cylinder. That bolt is actually hollow, allowing fluid to pass through it. If you do not have a fluid leak and your master cylinder IS full, then you likely have a master cylinder which is worn, but NOT worn out. I have seen this many times on automobiles. FIRST make certain that you do not have ANY air in the front brake system. Pressure OR vacuum bleed, if possible.

Good luck. . . and get this fixed before it fails at a critical time!!!!

If you're not losing fluid, then it sounds like the master cylinder seals are on the way out allowing pressure to escape/not be built up in the first place.

Another possibility is a partially siezed caliper. Check the caliper first (it's free) and then the master cylinder and the lines which can bulge under pressure with age.