2003 280 txt master cylinder question

[tpo]

Hello,

 I just bought my first trials bike, an 03 txt 280 edition. The brakes are awful. It has the 4 piston hebo calipers. I see no evidence of fluid weep or flexing between the caliper halves. I cleaned the discs with brake cleaner and soap and water and replaced the front pads(they looked the worst and i only had one spare set) and replaced and bled fluid. They got quite a bit better, but still don't have the snap that they should. Both rotors are pretty cooked, with discoloration and grooving, so I will be replacing them. But I have a question about my front master cylinder. When I was replacing the fluid and I had the top off, when I squeezed the brake lever the fluid would shoot up a bit out of the reservoir. This is standard behavior per my experience with other bikes. But when I squeezed lever again, the fluid shot up higher. And when I squeezed a third time, it shot about a foot in the air. Always this pattern of threes, and I did it about 20 times. Is this normal? Seeing as how very consistent each 'series' was, I have to think my master cylinder is working properly, but it seems odd.

Opinions? And a good source for replacement discs?

 Many thanks 

John

[thats_a_five]

I am not an expert on those calipers but is sounds like there is still some air in the system.  Brakes on trials bikes are notoriously hard to bleed completely.  Many people back bleed with a big syringe.  I finally bought a vacuum bleeder ($20 at Harbor Freight) and it works awesome. 

Discoloration indicates they have been hot as you probably know.  Unless it is extreme, it is not a big problem.  You can remove a lot of it with some 150 - 200 grit emery cloth and get back to a shiny metal surface. 

If you are still not satisfied, here is an old trick.  Ride a couple hundred feet with light pressure on the brakes.  Get them hot but not glowing.  Immediately spray them with the garden hose.  Do this 2 - 3 times.  I don't know why this works, I know it does.

Good Luck. 

I see you are in Oregon.  There is a great club in the Portland area.  Columbia Observed Trials Assoc. (COTA).

[tpo]

Thanks guys. I have a mityvac that I used to help bleed them. I had to get midieval and use the syringe tho. I tried putting a new o ring between the caliper halves but I wasn't satisfied with the fit of the ones I found, so I reinstalled the original.  I did do the water hose trick, that worked pretty well, thanks! Rotors are looking decent now. But still are missing power. I'm gonna keep riding it and bleeding it and see how good it gets. Once I'm satisfied that I have shook all of the bubbles out then I can make a decision about what's next. I do agree this caliper design asks for trouble.

Thanks!