[Lph008]

I'm having a problem with a used uforce i bought. The brake pedal is stiff but it doesn't return at all after you push it down. It was like this when I bought it, the rotors were gouged so I put all new rotors and pads on all 4 wheels. Replaced the master cylinder also. Pedal still sticks down, i have to manually pull it back up

[NMKawierider]

There is a spring in the master for return but...if it can't get the fluid back, it won't return. I would look for a bad proportion valve or something in line that is preventing fluid return.

[Lph008]

Any idea where the valve is? I dont see it in the parts diagram. Brakes worked fine before I replaced everything, just the pedal would stick down. From what I've read about the valve and the common signs, it doesn't seem like that would be the issue. It doesn't do any of the usual symptoms of a failing valve but who knows.

[NMKawierider]

I don't see one either...So the new master without installing it worked fine..right? Maybe there is a pinched line or some over-tighted banjo ends somewhere

[Lph008]

Yes the brakes worked before I replaced everything, they also work now but the pedal doesn't spring back at all. I traced the lines and dont see any kinks or damage. I have fluid at all 4 bleeders, used mighty vac to bleed the system

[NMKawierider]

So wierd. Anything with the res tubes?

[Lph008]

No. I dont get it either. I'm curious though, is the spring on the brake pedal responsible for the pedal returning or is it the master cylinder arm?

[NMKawierider]

No. I dont get it either. I'm curious though, is the spring on the brake pedal responsible for the pedal returning or is it the master cylinder arm?

It should just counter the weight of the peddle and ensure the peddle comes all the way back to the stop or the end of the master's plunger. Should be a little play at the top to ensure the master is completely topped-out against the end...and t should be able to do that on it's own. Like I say the only time I've seen when it couldn't is when the plunger is binding because of a flipped/damaged cup or trash being in it or it couldn't get the fluid back because of a bad prop valve or crushed line...or it couldn't get the fluid back to the res because of back pressure or plugged line. Your rotor scaring says it has had this issue for a while. The spring in the master is very light and if the peddles spring is too weak, it might be able to hold it down. Does the master's plunger come out on it's own when you raise the peddle? If so... 

[Lph008]

Yes the plunger returns on its own. When i remove the plunger arm from the pedal, the pedal still doesn't return at all.

[NMKawierider]

Missing or broke spring?..or maybe it was meant to rely solely on the master's spring but it was never strong enough. I might be temped to put a baby-bungee cord on the peddle to help it return. Something.

[Lph008]

I stopped at the dealer on my way home today and picked the mechanics brain. He said he's never heard of this, he said if I replaced the master then he would look at the spring on the brake pedal next. He said maybe it came off at one point and the previous owner just put it back on without the proper tension.
Well I tried messing with the spring but theres no way to wind it around again to add tension. He thinks it's definitely something in the pedal but idk. They're a newer dealership for cfmoto so im not sure. They didn't have a spring in stock so I guess I can order one and try that....out of ideas here

[NMKawierider]

I stopped at the dealer on my way home today and picked the mechanics brain. He said he's never heard of this, he said if I replaced the master then he would look at the spring on the brake pedal next. He said maybe it came off at one point and the previous owner just put it back on without the proper tension.
Well I tried messing with the spring but theres no way to wind it around again to add tension. He thinks it's definitely something in the pedal but idk. They're a newer dealership for cfmoto so im not sure. They didn't have a spring in stock so I guess I can order one and try that....out of ideas here

Rig a bungee for now.

[Lph008]

Ya im gonna have to use a bungee for now. Also the mechanic said there is a proportion valve for the rear but he said he's never had one go bad or malfunction but Doesn't think the symptoms point to the valve at all.

[NMKawierider]

Ya im gonna have to use a bungee for now. Also the mechanic said there is a proportion valve for the rear but he said he's never had one go bad or malfunction but Doesn't think the symptoms point to the valve at all.

I don't see one in the breakdown anywhere. Has to be built into the master...IMO

[Lph008]

I know me either. He said because there is only one brake line coming off the master going to the rear, there had to be one where they split off to both rear calipers. They're a newer dealership right by my house, less than a mile away. I drove it there about 30 min after I was already there but the mechanic was busy and couldn't look at it quick