Front brake

I had a bit of a get off when I first got my bike, ended up damage'n the front wheel and rotor etc, but since then the front brake has had a super soft feel too it, it's got a heaps spongy feeling and has to be pulled preety hard to even think about locking up, and I even upgraded the front rotor to a oversize kit, would it be the actual brake line may have been damaged and I just can't see it ?.

Check the alignment of the caliper to the rotor. If, looking at the "top" of the caliper with the axle lined up behind it in your view, the caliper twists at all as it's applied, that will cause a spongy feel and a loss of performance.

My dad was working on my 450's front break because it was spongy and he couldnt find out what was wrong with it he tried a few things and took it out and the front breaks locked up at around 45mph he ended up breaking his hand.

What year model? Does it have a replacement or original equipment brake lever?

it was a 08 and yeah i had a aftermarket sunline V-1 lever on it.

it was a 08 and yeah i had a aftermarket sunline V-1 lever on it.
The '08 has a different master cylinder, and requires a different lever than the '07 and earlier models. It's the same lever as used for '07 and later YZ250F's.

The problem is that just mounting an earlier lever pushes the M/C piston in far enough that it closes off the the M/C fill port, which is supposed to be open when the lever is released. When this happens, the fluid expanding from brake heat has no place to go, and the trapped pressure applies the brake instead.

http://www.thumpertalk.com/forum/showthread.php?p=5844853#post5844853

Thanks for the link Grey i showed my dad it and he had a look at my lever it turns out it is a 07 lever. looks like im going to be selling that lever.

Check the alignment of the caliper to the rotor. If, looking at the "top" of the caliper with the axle lined up behind it in your view, the caliper twists at all as it's applied, that will cause a spongy feel and a loss of performance.

I installed new 270mm kit and a new braided brake line and now have got a spongy lever and poor braking performance. I now noticed that the rotor is slightly bending when the brake is applied - that must be the problem. What can cause this and how to get it aligned right?

See if there's a way to shim the caliper so that it lays flatter with the rotor. It could well be that the pads simply need to wear in to match the angle they're sitting at, but that may take a while. You can check the contact pattern of the pads to see which way they are tilted.

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