Topic: need help with a radial master cylinder

[yodagruv]

help, please. I've installed a radial master from a 2006 suzuki GSXR on my 75 CB550 with a dual front disc conversion (basically double-stock discs.) I know there's no air in the lines, I vacuumed fresh fluid through the entire system from the master bleeder out the calipers. I have no lever pressure and it seems that nothing is being pulled from the reservoir. I've pulled the MC apart and cleaned it all out (pretty clean to begin with) and there's no crud blocking anything.

theoretically this MC should push two cylinders easily since I think the oem calipers it pushes have 8. any suggestions?

[grcamna2]

Could it possibly be air bound, or maybe the ratio of the size piston in that master cylinder is not compatible w/ the caliper applications ?!  What size or type master cylinder usually pushes Vintage Honda CB550/750 dual disc set ups & what size diameter is the standard piston used for that dual disc system from Honda ??
 
yodagruv, I think someone will come along w/ the specs for that on the forum here & you may have to change master cylinders. I have a good used CB750K4 master cylinder that needs a rebuild I can sell you,if that will help.

[MCRider]

See my post on your other thread. You may not like the performance of your choice MC, that's a separate issue. It should still bleed out all right.

Bottom line: If you know the MC is OK, then you have air in the line. You may have to bleed each joint. You may have to remove a component and hold it up so the air can become untrapped.

I just did mine and it was hard till i discovered the trapped bubble. Then bam.

[yodagruv]

ok, I'll try bleeding again or force it up the other way...

let's say just for a moment that my only problem is that no fluid is being pulled from the reservoir. is it more likely that the piston needs a new o-ring? I can't get it to bleed from the MC bleeder using just the handle and no fluid is exiting the reservoir. there is no blockage in the MC/reservoir.

[yodagruv]

btw, this is a 19mm MC

[scottly]

A 19mm MC, with two 38mm calipers will result in a VERY stiff brake lever, once you get the air out. Look for a smaller MC; 14, 16mm max.

[verslagen1]

1st issue, don't know specifically about about the gsxr master, but the savage master won't pump up from dry.  Either you have to have patience or a vacuum pump.

Fill the master with fluid, set back and have a beer.  before you know it, all the fluid drained out on the floor.   

[grcamna2]

Did you try removing your MC from the cycle & bench bleeding it yet...the MC is the highest point where the air always rises to;I would try bench bleeding it first to get it pumping & then re-install it; bleed the union joint at the MC after that.