Hello,

I'm assisting with repair on the above bike and the front wheel has just been replaced and now front brake has gone soft, the lever is all the way to the bar b4 getting reaction, could this be air in system (even tho we didn't open up the brake cylinder or pipe) or somethin a bit more serious?

 

what year??
Usually if an old brake system hasn't been maintained, the fluid starts to harden.
It's kinda like plaque on teeth. When you pushed the pads back, the force loosened some solids in the system and is now either blocking a passage in the master cylinder, or stuck along the plunger seal in the handle, and seeping pressure.

Remember: change fluid yearly!!!

 

Thanks for post have bled system and brakes can firm up but tend to soften after several braking instances assume this would mean master cylinder probs? Bike is a '99 and there are no signs of leakage anywhere along pipes or cylinder

 

Did you guys change the pads out? Is the new rotor (if different) thicker than the old one? You might have to get the new pads to seat.

 

like deej said it may just needs to be seated,, or you got them way to hot

 

All I know is if I change pads and push the piston all the way in on any other braking system, it takes a few pumps to get the thing to settle down.

 

+1 to the changing of fluids yearly, and of the pads needing seated on a new install.

Since the klr does not have an M/C bleeder,

1) Remove the reservoir cap, check that there is plenty of fluid in the reservoir.
2) With the reservoir cap off, slowly pump the brake lever several times until no air bubbles can be seen rising up from the bottom of the reservoir. This bleeds the air from the master cylinder end of the line.
3) Install the reservoir cap.
4) Remove the rubber cap on the bleed valve.
5) Attach a clear plastic hose to the bleed valve on the caliper, running the other end of the hose into a container.
6) Pump the brake lever a few times until it becomes hard and then, holding the lever squeezed, quickly open (turn ccw) and close the bleed valve. Then release the lever. Repeat this operation until no more air can be seen coming out into the plastic hose.

Got this out of my klr600 manual

 

Look in the bottom of the resivior (???) there should be 2 holes, one big (push) and one small (relief). the small hole will clog first, which prevents the master cylinder plunger from equalizing. utlimately just rebuild it. Brake fluid is corrosive and causes damage as it ages.