08 MTX brake issues

[Tookes]

Ok guys any suggestions to my problem with my brakes on my 08 Nytro MTX with Impulse Turbo? My dealer, my friend (very knowledgeable sled guy) and myself (twice) have bleed the brakes, looked at the diaphragm, calipers and checked the disc for warping and everything looks fine. I still have to pump the brake lever twice to get the brakes to work properly. Help!! I attached the Yamaha manual diagram to help make things easier. Thanks

 

[Hillclimber]

Interesting question, I too have noticed some odd brake behavior and didn't know what to make of it.
I have a loss of brake pressure only after long steep climbs. Doesn't happen on trails, just after I've been climbing wide open @ 8-12lbs of boost. I turn out (at the top of course) and grab some brake and it'll squeeze to the bar almost. Pump it a time or two and then it's right back where it belongs.
I'm on an 08 with MCX boost, I don't think it is specific to either brand turbo Tookes.
I've got a theory, boosted Yammies climb hills so high and steep that when you turn out at the top the little air bubble in the reservior lines up with the hydralic brake line.

 

[Tookes]

Yes that is what mine was doing in the beginning when I would climb, but now it is happening more on trails as well?????

 

[bholmlate]

Is there a extreme heat source anywhere near or vented directly on the brake line or caliper that could be transfering enough heat to them to boil the brake fliud? The rotor is vented so it should be able to disipate heat pretty well but there is not a lot of fliud in the system to dissipate any additional heat. Have you tried using higher temp brake fliud Dot 5?

I know turbos generate a lot of heat maybe try sheilding the brake line by wrapping it with another rubber hose to see if that makes a differece. If the brakes hold presure after you pump them it doesnt sound like there is any type of air leak. If the brakes are acting normal in your garage before you ride that pretty much eliominates any issue with a bad seals letting air into the system.

 

[Crewchief47]

Check the rotor for run-out or the caliper not sitting square with the rotor. Watch the caliper closely in the shop while playing with the brakes. Any movement besides parallel with the jack-shaft is bad. Movement in this area or a warped rotor will effectively push the piston back into the caliper and you will have to pump the brake to get the pad back out to the rotor. I would have started with the fluid but you said you've bled the system and i assume have added fresh fluid while doing that.

 

[pablo]

This was happening to my sled.It was the banjo bolt that goes into the caliper that was a little loose.

 

[Tookes]

Pablo, what number on the diagram is the banjo bolt? Thanks

 

[towerrigger]

#15

 

[Tookes]

Thanks for the input, it turned out that the rotor chewed up one of the shims and the rotor was not centered in the caliper and was making the inside brake pad do all the work and the rotor was rubbing the side of the caplier. New shim, new pads, fixed! before after