front end vibration under braking

when i pull the front brake lever i get vibration in the front end.
this is not with light braking but happens with moderate to heavy front lever usage. can use the rear peddle hard, moderate or light and no vibration.

any thoughts i have 12k on the bike

 

Most likely a warped rotor.......a dial gauge will be able to detect and measure the extent of the runout.

If the rotors are within runout specs then you need to start checking front end component bolt torque, brake pad wear patterns, tire wear pattern, wheel bearing condition, caliper operation, steering head bearings, fork tube alignment. Give the front suspension and front brake components a thorough check.

 

Thank you,
I have just replaced the brake fluid and noticed it.
under hard braking only.

 

Check front tire for cupping. A likely cause. Experienced the same with mine.

 

I had that problem before and replaced the front brake rotors. No more vibrating now.