Scarab bleeder screw

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gerard collier
Mariana
Posts: 38
Joined: Mon Aug 22, 2005 9:16 am
Location: simi valley ,ca

Scarab bleeder screw

Post by gerard collier » Fri Jul 27, 2007 9:07 am

Has anyone drilled and taped a scarab caliper for bleeder ??
there is a perfect spot on the lower section.
I am reanodising,rebuilding and replacing the pistons so I figured
what the heck add a bleeder ?????????

wdietz186
Cagiva Alazzura
Posts: 701
Joined: Sun Sep 10, 2006 5:40 pm

Post by wdietz186 » Fri Jul 27, 2007 8:19 pm

Gerard, Adding a bleeder might be a good idea But! it should be located at the top of the caliper to allow the air to be pushed out of the caliper.You might also have a problem machining the seating surface for the bottom of the bleedscrew. I would leave it as it is. Bill

Den
Mach 3
Posts: 89
Joined: Fri Apr 09, 2004 6:02 pm
Location: Florida, USA

Post by Den » Fri Aug 03, 2007 4:11 pm

m
You don't need bleeder screws on the calipers to bleed your brakes.

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 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 discs. 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 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. 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.

m

dukabmw
Cucciolo - the Lil Pup
Posts: 5
Joined: Tue May 31, 2011 5:07 am

Re:

Post by dukabmw » Wed Dec 09, 2015 6:42 pm

Den wrote:m
You don't need bleeder screws on the calipers to bleed your brakes.

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 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:....... etc


m

I'm going to try this method, but the rear brake is the hard one as the brake line goes up and down, leaving air trapped. I'm going to remove the rear caliper and try to tie it up higher and use the caliper bleed screw so hopefully this works easily......

Den.
Cucciolo - the Lil Pup
Posts: 2
Joined: Fri Jul 06, 2007 9:24 pm

Re: Scarab bleeder screw

Post by Den. » Wed Dec 09, 2015 7:10 pm

Let us know how it turns out.

Macdesmo
750 GT
Posts: 165
Joined: Tue Oct 07, 2008 2:35 pm
Location: Wide Bay Australia

Re: Scarab bleeder screw

Post by Macdesmo » Thu Dec 31, 2015 8:46 pm

The photo shows what the original 1974 Ducati 750 SS Scarab brakes look like. I hope this may help.
Ian
Image

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