Ven05 Brake issue

[Steve Libretto]

Hoping someone can help me here…. I have an issue with the outboard piston on the rear caliper retracting back into the caliper when the brakes are released thereby giving me a deep pedal, and not as much rear braking force due to the fact that most of my pedal travel is being used to bring the piston to the pad…. When I pump fast a few times it will hold for a bit, but then slowly get “sucked” back into the piston. I’ve rebuilt the master, and now the caliper but it still does this. I ran the end of last year and all of this season so far with no issue.
Any ideas???

[Chris Rock]

Steve,

I’m guessing but it sounds like either there isn’t enough fluid in the system and/or the rotor isn’t centered between the pads correctly.

[Steve Libretto]

Thanks for the suggestion Chris, there was/is enough fluid, and the rotor seems to be centered. The problem is that with those brakes, there are no return springs on the pads, and the pistons should just release the pressure from the pads, and remain “out” by the pad, but what’s happening to here is that the outboard piston is retracting back into the caliper by 1/4 to 3/8″. The other side (inboard) regales properly but doesn’t retract back into the caliper. It’s really strange and I can’t figure it out. I may try to vacuum bleed them tonight, maybe I boiled the fluid and there’s trapped air in there, but I did bleed them out regularly last night with no success. I’ll keep the thread posted if I figure it out… If there are other thoughts or ideas, I’d be glad to try them!

[Chris Rock]

Steve, when you bleed them, put a piece of fuel line over the bleeder valve. This let’s you over fill the master a little and when you pull/pump the pedal to force fluid through this gives the fluid somewhere to go and you can see when the air bubbles stop. Also,  I never could get the ven05’s quite right if I tried to center the rotor in the caliper. It always seemed to want to be a little closer to one side than the other to get the pads to contact the rotor at the same time.  I usually leave the brake hub loose so it can move on the axle, pump the brakes a few times and then tighten the hub while someone holds the brake on.

[Brian Degulis]

It’s probably the way your bleeding them. The system is not full or has traped air. If you have the flat tops with no fill plug on the masters then it’s best to bleed backwards. You should take the caps off and open the bleeder. Then force fluid into the bleeder untill clean air free fluid flows out of the master. I use a pressurized canister but something like a turkey baster works also. Anything that can force clean air free fluid thru the system will work.

 

Brian

[Walt Gifford]

Maybe a dumb question but do you have the right rotor on it? The Ven05 rotor is a little wider than the standard euro rotor.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Steve Libretto]

Brian,
I do have the flat tops on the masters. If I bleed them reverse…. Does the pedal need to be held in the fwd position, or just leave the masters alone? I’m guessing that ill have to empty remove some fluid from the master as I go also?

Walt,
I don’t believe there are dumb questions…. It is to the best of my knowledge a Ven05 rotor. It is the wider if the 2 different widths that I’ve seen.

As I said….this is a new issue, these brakes were flawless till now. After rebuilding the caliper it doesn’t seem as bad but the one piston does still suck back in a bit. It’s most noticeable while bleeding… When I pump, then hold, and open the bleed screw, then close bleed screw and relapse the pedal the one piston sucks back in about 3/8″

[Brian Degulis]

Steve don’t mess with the master’s lever at all. Just pull the top cap off and force fluid thru the bleeder untill clean air free fluid is overflowing the master then close the bleeder while it’s still flowing. Set the level in the master and your good to go.

 

Brian

[Walt Gifford]

You don’t have to reverse bleed the brakes. Ven05 is the easiest brake system to bleed I’ve ever seen. Just make the bleed screw the highest point in the system and don’t let the MC reservoir empty out and suck air when you lift off the pedal. Fill it as you lift if you have to, lift off the pedal slowly, your MC seals are working in reverse you don’t want them leaking air, give the fluid time to get past the little holes. When you open the bleed screw and press the pedal, close the bleed screw before you run out of pedal travel. Use dot4 fluid. If you use the wrong fluid it will work at first then the seals will soften and cause problems. Did you remember the Oring between the caliper halves? That would explain why one side is moving more than the other.

Hope that helps,

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Steve Libretto]

Walt, almost forgot the o-ring between halves but noticed as I was putting them back together…. I never closed the bleeder prior to going full pedal, but I’ll re-bleed them and do that. I had been using castrol GTLMA, because it was recommended to me by a popular online retailer, but was recently told to on use Dot4 so after the rebuild, I drained all, and used dot4

[Steve Libretto]

I think I may have found a contributing problem…. The caps on the master cylinders have a minuscule hairline crack on the back side lip of the cap where the vent is. I’m it sure if this would cause the issue I’m having, but maybe the caps aren’t sealing properly all the way around since they are obviously no longer perfectly flat?

[Walt Gifford]

The cap on the MC just keeps dirt out and fluid from sloshing out. They don’t seal the pressurized side of the system.

I checked mine, pedal moves 1-1/2″ and the (new) pads move 1/16th total for both sides. Brake rod is on the top hole on both pedal and lever.

Are you pads almost gone?

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Steve Libretto]

Walt, my best guess is that the pads are about 1/2 life. They are still the set that I bought the kart with. Is the groove that is in the pad a good indicator of when they’re done? I could measure what’s left with a caliper, but I don’t know what the thickness of a new pad is to compare. Thanks for all the input And help Walt

[Author]

Posts