Dragging Brake, once per rotation

[qnp9999]

Hi I'm new to the forum and new-ish Kymco owner.  I have a 2009 super 8. I bought it used with 3500 miles on it about 3 months ago. I Love it so far, but I have one nagging issue that is driving me nuts.

The front brake was dragging and had a slight pulsing in the lever as soon as I got it.  Initially I thought it had to be a warped rotor... an easy fix. I inspected the disc more closely and saw the darkened portion where the pads were wearing it down and decided to replace the rotor and pads. 

That did not resolve the issue.  New pads and rotors installed, I was now able to hear the brake dragging simply by spinning the wheel manually (thicker newer pads is my guess).

So I took it to a local shop and they said they didn't work on Kymco's but thought it must be the wheel.  Since it's not spoked and apparently didn't have a way to mount it to check the trueness I decided my best bet was to buy a new wheel.

The wheel, tire and rotor came in today, and after installing I can still hear the disk dragging once per rotation.  It's driving me mad!  I've spent far to much money chasing this issue, and still am no closer to resolving it than I was when I started. 

My only other thought is that it must be the axel, as it's the only component I haven't replaced.  But I don't understand how that could be it.  Because it doesn't spin and therefore if it were bent, the brake would be constantly dragging rather than dragging once ever rotation.

Hopefully someone with more knowledge than I has a few ideas. Thank you in advance for any help!

[streido]

Take the caliper off and strip it down and give it all a good clean and regrease it all up. You can try this 1st leaving in the pistons and it should work. If not then the pistons themselves may have corrosion on them and may be sticking. See how they look. I had the smae issue on my Agility but after stripping down,cleaning and greasing up all moving parts and pins with copper grease its been fine nkw for months. Grease the back of the pads too where the piston hits it.

[skippy]

+1
i had the same problem. quick clean and grease. one of the pistons had coroded. so kept pumping the piston back and forth. still not fantastic but no sticking problems. also consider changing the brake fluid as if there is water in the fluid this is the problem.

[qnp9999]

Thanks for the quick replies!  I re-read my original post, and realized I may have not explained the actual issue very well.  I think cleaning the calipers could definitely do some good, however I've toyed around with them enough off the scooter to know they aren't sticking, the piston slides smoothly as do the pads/caliper on the slider pins.

The brake is not dragging constantly but instead catches for a small fraction of the complete revolution in the same spot every time.  That in addition to the pulsing of the lever, suggests to me that somehow the rotor is not spinning correctly through the caliper.  Meaning it's position between the caliper is fluctuating throughout the revolution of the rotor. 

If it were simply an issue of the brakes sticking or dragging constantly all the time it seems like there wouldn't be a small specific part of the rotor that catches on every revolution.  I will definitely take the advice of taking the caliper completely off and giving it a thorough cleaning, but mechanically I can't wrap my head around how that could be the entirety of the problem.

[CROSSBOLT]

Have you checked the bearings? Is the rotor the same thickness all the way around? Pulsing lever is usually an indication of warped rotor or a "lump" in the rotor. You went the full mile on parts and the problem did not go away. Maddening. Also the local "experts" did not seem to be of much help.....

Karl