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What's the secret to bleeding front disc brakes after opening the system?

I've bled many car systems and have never run into these issues. Yesterday trying to bleed the brakes on a CRF230 after changing pads we had to remove the caliber, manually manipulate the plungers before I could finally get the system to pump fluid so I could bleed the lines.

Today, after replacing the front brake line on my daughter's KX-100, same issue. I can't get any pressure to build up in the system in order to bleed the line? What am I doing wrong? Is there something unique to motorcycle systems?

I've bled many car systems before myself. I've always found though, that for whatever reason front brakes on motorcycles of any kind just take a LONG time to bleed and always seem to be a PIA. A couple months back i finally got my front brakes operational after the previous owner had the entire system off the bike for over a year. So you could imagine i had alot of pumping to do. Heres what i learned:

Make sure you have the entire system tight and no leaks present, no seized calipers or any of that. Pump the lever ALOT. Try to go about 5-8mins at a time before you open the bleeder. Keep cracking the bleeder after each pump session until you see some fluid. At that point you know you're getting closer. Don't stop until you see a nice steady stream of fluid out of the bleeder right when its cracked open and the lever feels firm and grabs quickly. Always make sure the master is full as your pumping, top off as you go. It usually does take a while especially if you took the caliper completely off for any reason. Also make sure your brake line/hose is routed the same way it was before, no kinks or in proper bends. Make sure the line doesn't travel above the master cylinder at any point.

Theres a neat trick my friend taught me to get a real nice, firm lever. Zip-tie the lever to your bars as tight as you can over night after you've bled the system and gotten a nice steady stream of fluid out of the bleeder. Cut the zip-tie off in morning or early afternoon and you'll have real nice and firm brakes with no sponginess. Hope this helps somewhat.

What would the zip tieing achieve? do u have to re bleed the system after the zip tie comes off?

I just did this. One trick that worked and sped up the process and really helped was using a syringe and pushing the fluid up from the caliper. After that I was able to get them firm pretty quickly.

I just went through this myself and have to agree it is one of the worst pains in the rear I have been through to bleed brakes. This is my first dirt bike, but I have had street bikes for years and have never had to put in the amount of effort to get a street bike system bled as I did for my KDX.

That said, here's what I can offer from my experience. Most of it is the same as or just adds a little bit to what 92kdxRider and others said.

I agree that keeping the "hump" in the brake line down below the master cylinder while bleeding is important so air does not get trapped in the high spot in the line. I zip tied my line down and removed the zip tie when I got done.

It seems to me that initially filling the system can be done with the syringe/push method or the Mity Vac (vacuum bleeder)/pull method. Either should work and gets you started. The syringe method is sure easy. You could use 92kdxRider's 5-8 minute pump method too, but forcing the fluid one way or the other gets you going sooner IMO.

After the intial fill, I used a combination of MityVac and the bleed method in the manual (pump lever, crack/retighten bleed valve, release lever) to get the worst of the remaining air out. Then I removed the MityVac and went strictly with the method in the manual to get the last of the air out. It seems to have worked OK. Lever is firm, but not outstanding, and braking is good.

I also did the trick of tying back the lever and leaving it overnight. This has worked for me on other bikes and seems to have made a small improvement on this one. I have no idea why this works because the path to the reservoir is cut off when the lever is applied, but it seems to work. No rebleeding is necessary after trying this trick.

I may bleed mine one more time for good measure.

Hope this helps someone out.

I just use a mity-vac, easy peasy

Mr. Wibbens wrote:I just use a mity-vac, easy peasy

That was certainly my expectation, but not my experience in reality. See my desparate cry for help here

http://www.kdxrider.net/forums/viewtopi ... highlight=

I have since rebuilt my caliper and master cylinder, then charged and bled the system and am back in business. But it was not as easy as hooking up the MityVac and sucking fluid though till bubbles don't show up. I thought it would be that easy. That has been my experience on other bikes, even with the brake system starting dry, but not this time. Others seem to be having the same problem, mainly with dry systems.

First time I tried it I got nothing but bubbles...

Then on a hunch I removed the bleeder and wrapped the threads with teflon tape

Been working fine ever since

Bouillion wrote:What's the secret to bleeding front disc brakes after opening the system?

I've bled many car systems and have never run into these issues. Yesterday trying to bleed the brakes on a CRF230 after changing pads we had to remove the caliber, manually manipulate the plungers before I could finally get the system to pump fluid so I could bleed the lines.

Today, after replacing the front brake line on my daughter's KX-100, same issue. I can't get any pressure to build up in the system in order to bleed the line? What am I doing wrong? Is there something unique to motorcycle systems?

I'm glad I'm not the only one that has trouble getting the air out. Doesn't matter which brand - all of them give me problems!

I still think that the 12 pack gravity bleed method worked great.

rbates9 wrote:I still think that the 12 pack gravity bleed method worked great.

I tried the 12 pack and I have a little buzz but, still have no brakes!!!!!!!!!! May have to run to the drive through liquor store for more?

Handy device if you don't have a vac, but they come in handy at other times:

http://www.rockymountainatvmc.com/produ ... ilyId=9518

2nd the teflon on the bleeder.

I've only tried it once on the wife's TTR, and i followed the instructions in the online KDX manual and it worked like a charm with no special tools.

I'm going throught the same thinhg. Changed to a braided line up front and can't get the lever firm. Been using the reverse bleed syringe method. probably moved 12 of fluid throught system. tryin teflon tape next. i hope hope hope it helps.

I finally got it done. First I removed all the fittings and applied teflon, then I used a small oil can pump to pump fluid up from the bleed fitting. Worked like a charm.

Thanks for all the advice.