Disc Brake problem

i converted my rear disc brake suzuki s40 to a dual disc brake, two piston calipers on each wheel on my trike conversion. installed a proportioning valve, bled the system 3 times, spilled some fluid on the wheels and cleaned it off with brake cleaner. the problem is the rear brakes are only strong enough to hold bike in place at a red light or stop sign. will stop from an idling speed w/some effort. any ideas would be appreciated.
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[QUOTE=nhbiker1;248278]i converted my rear disc brake suzuki s40 to a dual disc brake, two piston calipers on each wheel on my trike conversion. installed a proportioning valve, bled the system 3 times, spilled some fluid on the wheels and cleaned it off with brake cleaner. the problem is the rear brakes are only strong enough to hold bike in place at a red light or stop sign. will stop from an idling speed w/some effort. any ideas would be appreciated.
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You aught to know what type calipers it has. Brake pad material can make all the difference if the brakes are not spongy. If spongy, put speed bleeders on them and use a MityVac and suck out as much as possible then bleed the little remaining with just the speed bleeders. The two brakes off one m/c means there is a good possibility of air still int he system. Sometimes it seems almost impossible to get all the air bubbles out. If the pedal is firm, you have good pads, time to look at a m/c with larger diameter plunger. If you are using the original and it was intended to provide hydraulic pressure to one pot and you now have four, then it may not be large enough diameter.

[QUOTE=wiredgeorge;249213]You aught to know what type calipers it has. Brake pad material can make all the difference if the brakes are not spongy. If spongy, put speed bleeders on them and use a MityVac and suck out as much as possible then bleed the little remaining with just the speed bleeders. The two brakes off one m/c means there is a good possibility of air still int he system. Sometimes it seems almost impossible to get all the air bubbles out. If the pedal is firm, you have good pads, time to look at a m/c with larger diameter plunger. If you are using the original and it was intended to provide hydraulic pressure to one pot and you now have four, then it may not be large enough diameter.[/QUOTE]
thanks,
all parts are new to the bike. came w/the trike kit. master cylinder,calipers,pads,rotor,braided lines. we had to add a proportioning valve and a linkage from original pedal(which was a drum brake setup)

I've heard if the push rod is not adjusted correctly the brakes will do what you are describing. If the rod is not allowing the piston to return far enough fluid will not be sucked back into the chamber. At least that is something I have heard.

[QUOTE=vw driver;249525]I've heard if the push rod is not adjusted correctly the brakes will do what you are describing. If the rod is not allowing the piston to return far enough fluid will not be sucked back into the chamber. At least that is something I have heard.[/QUOTE]
now that sounds possible. i'll have to check that out. thanks