Need a little help here....

[SPDguns]

I have an '07 Yamaha Grizzly 350 4WD I bought new. The front brakes are locking up and when I squeeze the brake lever, it absolutely will not budge, no play, no spongeyness or whatever. I completely rebuilt the master cylinder and brake calipers with new seals. There are three flexible hoses and I replaced them too. All parts were Yamaha OEM. I flushed the fluid and bled the air out twice. It's still doing it. In order for me to ride the thing, I have to bleed the pressure off of it. After a while, the pressure will build back up.

HELP MEEEEEEEE......

 

[dlbleak]

Disc brakes I assume? Caliper slider bolts dry, rusted, corroded?

 

[SPDguns]

Disc. Caliper bolts slide good.

 

[Okie4570]

If both calipers are doing it, it only leaves the master cylinder imo. Not familiar with how that one is put together, is possible to install the cylinder kit pieces incorrectly?

 

[SPDguns]

Something is causing the system to pressure up on it's own

 

[SPDguns]

If both calipers are doing it, it only leaves the master cylinder imo. Not familiar with how that one is put together, is possible to install the cylinder kit pieces incorrectly?

No way. I stayed at a holiday inn last night

 

[swampratt]

When an automotive system allows the brakes to get tighter and tighter the more you use them and do not back off the rotor the issue is that
the master cylinder pushrod is not completely disengaging.

Make sure the brake lever is not keeping pressure on the rod/piston in the master cylinder.

Sometimes you will need to grind some aluminum off the brake lever where it contacts the piston.
This can be true if you have replaced it at one time.

Remove the brake lever and see if your issue goes away.
That is an easy test.

That is after you checked what @dlbleak stated.


Fluid needs to flow back into the master cylinder when you let off.
You know that though.

 

[O4L]

I had a collapsed line once that wouldn't let the pressure bleed off and locked up the brake. Maybe there is a pinch in one of the lines.

 

[SPDguns]

All lines are new factory Yamaha. The brake lever hasn't been modified, it did this with the old master cylinder piston and now the new one.

 

[SPDguns]

When an automotive system allows the brakes to get tighter and tighter the more you use them and do not back off the rotor the issue is that
the master cylinder pushrod is not completely disengaging.

Make sure the brake lever is not keeping pressure on the rod/piston in the master cylinder.

Sometimes you will need to grind some aluminum off the brake lever where it contacts the piston.
This can be true if you have replaced it at one time.

Remove the brake lever and see if your issue goes away.
That is an easy test.

That is after you checked what @dlbleak stated.


Fluid needs to flow back into the master cylinder when you let off.
You know that though.

I'm going to pull the lever and see if it still pressures up before I grind on it