Bleeding twin bleeder F08 brake calipers

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Aussiess
750 GT
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Bleeding twin bleeder F08 brake calipers

Post by Aussiess »

OK,
I am no expert on this bleeding process, but I am having difficulty bleeding and obtaining lever pressure on my 78 900SS F08 calipers (shaved calipers).
Can someone please point me in the right direction , there must be a simple technique. I have just fitted new braided hoses. I did not need to open the calipers at all.
Thanks.
Regards,
Grant
79 900SS , 82 MHR and 78 NCR Replica
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BevHevSteve
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bleeding

Post by BevHevSteve »

you saying you ONLY switched out the hoses? You didn;t touch the calipers or master cylinder? If yes, then you must have a large pocket of air in the splitter thing under the triple clamp, and/or you have one of the lines touching something to cause it to not sit flat at the banjo. Check everything carefully.

I did a dual line setup once, with both caliper lines going directly to the master cylinder using a dual banjo. It messed around with that thing for several hours until my buddy came over, took one look at it and asked me why I have the 2 banjos at the master cylinder lined up [stacked up the same] and wondered if they were touching eachother causing a bind.....

I removed the banjo bolt, installed new crush wahers and this time staggered the banjos just a bit, tightened everything up and bled the system in 3 mins.
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DesmoDog
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Post by DesmoDog »

You also need to be careful that the banjo bolt on the M/C isn't the highest point on the system. Numerous times I've had difficulty bleeding a system and as soon as I remember how I fixed it "last time", I lean the bike to get a better angle on the master cylinder, and without even opening a bleed screw it bleeds in about three pulls of the lever... you can see the air bleed out of the ports in the master if it's not a remote reservoir.

Don't squeeze too hard or once the air bleeds out the fluid will spray up and out of the master cylinder, all over the front fender and tank. Ask me how I know.
Aussiess
750 GT
Posts: 163
Joined: Sun Oct 31, 2004 6:51 pm
Location: Blue mtns, NSW, OZ

Post by Aussiess »

Thanks for the feedback, I did replace all the hoses, banjoes and washers from the MCyl to calipers.

I will attempt to rebleed taking into account the banjo at the MCyl being the high point, I have checked the banjoes and seals, all tight. I may try a "power pump bleed" system, I have been told they work well and I can access a pump.
Regards,
Grant
79 900SS , 82 MHR and 78 NCR Replica
Den
Mach 3
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Post by Den »

Here is how I bleed my brakes and it has never failed me. I am assuming that the M/C and caliper were correctly rebuilt and assembled.

First of all, I never bleed my brakes just to replace the fluid. It is so easy, that I always do a complete caliper rebuild/cleanup and start from scratch with a dry system. Because I keep the system clean, I almost never have to replace any seals in the calipers or M/C.

For a completely dry system:
With the M/C empty, remove the calipers and push the pistons in as far as possible. Re-install the calipers. With the bike on the sidestand, turn the handlebars to full right lock so the banjo bolt is higher than the brake lever. You may have to rotate the M/C on the bar to keep it level enough to add brake fluid. Pour in some brake fluid. Not too much. Leave the M/C cap off. Slowly squeeze the lever only about ½ inch. You should see little bubbles being forced from the rear part of the M/C piston coming up through the brake fluid from the rear hole in the reservoir. Keep making small squeezes. You are bleeding out the air that is trapped between the two rubber piston seals. After bubbles stop coming up, you will now be able to pump fluid down the brake line. Put the M/C cover back on and turn the handlebars full left lock so the brake lever is higher than the banjo bolt. Take the cover back off. Reorient the M/C so it is level again. You are now going to perform the same procedure to bleed the air from the lines. Without opening the caliper bleed screw, go ahead and slowly take a few full pulls on the lever, releasing the lever slowly. When you take a slow pull, you are pumping fluid down the line and displacing the air which wants to rise. When you release the lever you are helping to suck the air up the line to the M/C and you will notice the fluid level in the reservoir go down. Don't let the reservoir fluid level get low enough to suck air. Take the time to rap on the brake lines and banjo bolt with the handle of a screwdriver every now and then to break loose any stuck bubbles. Be patient. Soon, you should start seeing the little bubbles coming out of the front hole. This time they are coming up from the caliper as the fluid is flowing down. Now you aren't pumping the fluid down, it is already there. You are only pumping the air out as it is being displaced by the fluid. Now change your pumping to the little ½ inch strokes again because the air is all at the top near the banjo bolt and you are now pumping it out little by little. When the bubbles start to get real fine, you know that you are almost done. Keep rapping on the lines and tapping on the banjo bolt to make sure no air is stuck in any nooks or crannies. When the bubbles stop you are done. If you like, you can check your work by cracking open the caliper bleed screw and pumping a few handfuls. I don't bother. Sometimes the lever might still feel a little spongy when you're done. If you keep the lever squeezed and held back to the bar with a thick rubber band overnight, that will usually force free the very last of the hidden air bubbles, and they will make their way to the highest point of the system which is the M/C. So leave the bars turned full left lock and redo the little ½ inch squeezes the next day for that last bit of hidden air. This procedure works for me without having to ever loosen the caliper bleed bolts.

For a M/C replacement/overhaul with a wet system:
Assuming the system was working properly before M/C removal. Motorcycle on the sidestand, bars full left lock. With the cap on the empty M/C, remove the calipers and slowly push the pistons back in as far as possible. This procedure will push fluid into the M/C and displace all of the air at the top at the banjo bolt. Remove the M/C cap and with full strokes slowly pump the fluid back down to push the pistons back into contact with the disks. Don't let the reservoir run dry. When the lever starts to firm up, change your pumping to the little ½ inch strokes again because if there is still any air in the line it is all at the top near the banjo bolt and you are now pumping it out little by little. When the bubbles start to get real fine, you know that you are almost done. Keep rapping on the lines and tapping on the banjo bolt to make sure no air is stuck in any nooks or crannies. When the bubbles stop you are done. Sometimes the lever might still feel a little spongy when you're done. If you keep the lever squeezed and held back to the bar with a thick rubber band overnight, that will usually force free the very last of the hidden air bubbles, and they will make their way to the highest point of the system which is the M/C. So leave the bars turned full left lock and redo the little ½ inch squeezes the next day for that last bit of hidden air.
Bumbler
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Thanks Den!!

Post by Bumbler »

I've bled brakes on many machines and thought I understood things quite well...but after spending 4hours+ on my Pantahs brakes I was ready to burn the thing. :evil:

Followed your advice and had the whole thing done in 30min. The rubber band trick works a treat also.

Thaks Den...you saved a Pantah from a firey death. ;)
Bumbler.... '82 Pantah 600
Den
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Post by Den »

No charge ; )
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nottonight68
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Post by nottonight68 »

i agree with with den
i've been doing similar for years
i always go through that process 1st before opening anything up
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