radial master cylinder issues

[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?

 

[pugeyed]

tried pushing fluid up from the bottom in case its got an air lock

 

[yodagruv]

I don't think I have a way to "push" fluid. I assume that takes a specific tool.

 

[rockcitycafe]

the mc on that bike is probably a very small diameter, designed for moving a really small volume of fluid at high pressure, the calipers on modern discs are much tighter tolerance and move so much less than older calipers, that you're unlikely to be able to use it with the old calipers with any reliability.

 

[surffly]

You need to keep the ratio of the caliper size to the master size in a range in order to have the brakes work.
A "modern" master doesn't always mean better brakes...there is more to it then that.

Check out vintage brake for a ratio chart and info that might help

 

[yodagruv]

I'd been using an MC from a 2000 ST1100 and it worked fine, just didn't fit my new bar setup. where can I find that chart?

i've been assuming this MC is good but 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

 

[surffly]

http://www.vintagebrake.com/mastercylinder.htm

 

[joea]

there are several different m/cyl piston sizes and usually the larger piston is for duals (5/8) or larger metric sizes...to reverse bleed you use a large syringe and push fluid from caliper bleeder up to the m/c,google it and you should find an in depth explanation.
your off the mark on your assumption about 8 pistons vs what you have, you need to understand hydraulics ............should be a ton of info on that too..
good luck,joe@ vcycle