250 Bleeding Dry Line Tips

Alright, I bench tested the master today using the following video:


It appears to pass that test. Something is amiss. Will probably have to wait until Monday for my fluid to arrive :(
 
Bad news :( I bled and bled today and took a very close look at the pistons... I think one of them is cracked. When I squeeze the lever, I can see a small bit of fluid leak out between the piston head and body (the silver part and the black part on the OEM pistons).

It's a small bit of fluid, but I suspect that it's also drawing air back in.

May have to wait a couple more days while I order some new ones :( Most unfortunate.
 
Bad news :( I bled and bled today and took a very close look at the pistons... I think one of them is cracked. When I squeeze the lever, I can see a small bit of fluid leak out between the piston head and body (the silver part and the black part on the OEM pistons).

It's a small bit of fluid, but I suspect that it's also drawing air back in.

May have to wait a couple more days while I order some new ones :( Most unfortunate.

Unfortunate. I would go on eBay and see if I could find a whole caliper assembly
 
I just did the CR conversion on a YZ I built. Here is what I did:
1. Complete rebuild kits for master and caliper, new brake line, banjos, copper washers.
2. Cleaned both components, soaked in waste gas for a few hours. Sprayed off with brake clean.
3. Put new seals in caliper.
4. Filled lower piston cavity with dot 4, slid piston in and out to push air bubbles to upper piston cavity.
5. Filled upper piston, repeat until bubbles are out of banjo and bleeder holes.
6. Make sure the pistons are not stuffed in. 1/4-3/8 out
7. Pour more fluid into holes.
8. Install hose and banjo.
9. Install bleeder valve.
10. Push pistons in forcing fluid into brake line. Keep it elevated above caliper.
11. Same with master, fill plunger cavity with fluid, and stuff new seals and plunger in.
12. Install hose and banjo.
13. Fill reservoir with fluid.
14. Elevate caliper over master and install brake pads.
15. Install caliper on a rotor or equal thickness above the master.
16. Pump, hold, release bleeder, tighten bleeder, release lever.
Did this to my sons CRF (without the rebuild) soft brake, and bam, lit new gripped.
 
Thanks! I may have to try that approach. I bought a used caliper assembly off of eBay that should be here today. I'll try all the post rebuild stuff.

Thinking about replacing the seals on it, but the guy said the seals aren't that old. Not sure whether or not I trust it, but I must admit I'm a bit eager to get the brakes working on this thing. Is it safe to take the new seals out of my old caliper you think and put them in? Waiting another week for new seals again doesn't seem fun :(

If I could get reasonable braking with these seals maybe I could ride on these for a little bit and then order a new seal kit again (but at least I could ride while I wait :) )
 
I just did the CR conversion on a YZ I built. Here is what I did:
1. Complete rebuild kits for master and caliper, new brake line, banjos, copper washers.
2. Cleaned both components, soaked in waste gas for a few hours. Sprayed off with brake clean.
3. Put new seals in caliper.
4. Filled lower piston cavity with dot 4, slid piston in and out to push air bubbles to upper piston cavity.
5. Filled upper piston, repeat until bubbles are out of banjo and bleeder holes.
6. Make sure the pistons are not stuffed in. 1/4-3/8 out
7. Pour more fluid into holes.
8. Install hose and banjo.
9. Install bleeder valve.
10. Push pistons in forcing fluid into brake line. Keep it elevated above caliper.
11. Same with master, fill plunger cavity with fluid, and stuff new seals and plunger in.
12. Install hose and banjo.
13. Fill reservoir with fluid.
14. Elevate caliper over master and install brake pads.
15. Install caliper on a rotor or equal thickness above the master.
16. Pump, hold, release bleeder, tighten bleeder, release lever.
Did this to my sons CRF (without the rebuild) soft brake, and bam, lit new gripped.
I have just started out by sticking some flat stock between the pads and hanging the caliper on the ceiling beam in my garage and bleeding. Doing the cr to the yz 125 was the last time I did that in fact.
 
I have just started out by sticking some flat stock between the pads and hanging the caliper on the ceiling beam in my garage and bleeding. Doing the cr to the yz 125 was the last time I did that in fact.
Yep that works, it's nice to have extra rotors laying around, and a vice.
 
As far as I can tell, that definitely helped. I had someone hold the caliper higher than the master and then I pulled the bleeder under vacuum a couple of times.

It's way firmer than I've been able to get it so far but now I feel like I have forgotten how stiff it should be :) I've zip tied the lever to the bars for the night, but what's the best way to test the lever? A normal grip no longer takes me to the bars but I nice hard one with 3 fingers and I can still pull it back.

Thoughts on best way to test this?
 
As far as I can tell, that definitely helped. I had someone hold the caliper higher than the master and then I pulled the bleeder under vacuum a couple of times.

It's way firmer than I've been able to get it so far but now I feel like I have forgotten how stiff it should be :) I've zip tied the lever to the bars for the night, but what's the best way to test the lever? A normal grip no longer takes me to the bars but I nice hard one with 3 fingers and I can still pull it back.

Thoughts on best way to test this?

Sounds pretty close to me.
 
Then I think this caliper is good to go :) Pads have some life left in them fortunately, but I'm in for a headache when I go to replace them :( Looks like the guy stripped and overtorqued the cover bolt for the pad pin... Going to be a pain to get off. I just hope the pad pin itself isn't stripped like it was on my last caliper. That pad pin is thick and takes forever to get a drill into.

Thanks for your help guys!
 
In two occasions, I have rebuilt the master cylinder and bled for hours... I mean hours... to no avail.
Stumped, and not one to throw money at a problem, I tried a different master cylinder. Instant fix. There was no air in the system.

The immediate remedy was replacement of the master cylinder. Not a typical result.
Something was physically wrong with the original master cylinders and they could not be rebuilt.

Not saying this applies to your case, but in the 100s of brakes I've bled, on two bikes I wasted a lot of time.
-BIG DAN:thumb:
This. So after struggling with this for the whole last month (reverse bleeding, vacuum bleeding, raising caliper above master, etc.), I decided to get a used MC off of eBay. Instant fix :( I should've certainly tried this sooner! I rebuilt the master, but maybe one of the seals had a nick in it or something? They were aftermarket seals, so they could've just been no good, I suppose too. Thanks for your help guys!
 
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