Hey all!
Thought I got the scooter fixed once and for all, but in typical Harley fashion, the gremlin showed itself again and this time it hurt a little... The first test ride, the front brakes were dragging a little, but not to the point of locking up, so I flushed everything, and cleaned it all, and rode it 30 more miles with no issues. Just took it on another spin after changing oil lines, and the front brake decided to randomly lock down hard as I was taking off through an intersection with some loose gravel, needless to say, I ended up on my side with some road rash, and a broken turn signal. Anyway, what would cause the brake to randomly lock down? I plan on taking the whole front system apart and cleaning it with a fine tooth comb.

 

Sounds like some air in the system heated up and expanded , only other thing would be the master cylinder had no free play and pumped them up.

 

I was thinking it could be air too. After I got it back up, and was able to get it home, the brakes were normal again. Like I said, this thing will probably have a completely new front brake system before I ride it again. That hurt!

 

Corrosion inside the caliper will cause the piston to stick and prevent brake release.

 

Yeppers, pop the pistons out clean, lube ..
sticky caliper , heats up brake pads=they expand ,lock the front wheel.


know of a couple of fatalities caused by that .

 

Did you use a Harley Davidson service manual?

 

A few years ago this question was asked in a letter to Cycle World Magazine. Kevin Cameron, the magazine's tech editor's, response was that a brake pad dragging on the rotor caused heat to build up.

That caused the fluid to expand, causing the brake pad to be pushed harder against the rotor, causing more heat, more expansion, more heat, etc.. Eventually the brake locks up.

He went on to suggest that this was caused because the little hole, in the master cylinder which allows to fluid to return to the master cylinder after using the brake, is plugged up and doesn't allow the fluid to return to the master cylinder.

 

Several years ago I was headed to work at 70 mph when the bike started to slow down. I gave it more throttle but it kept slowing down. I realized it was the rear brake locking up. By the time I got it to the shoulder the brake rotor was glowing bright red and the caliper was locked solid. Called for a tow. By the time the truck got there the whole assembly had cooled and now the brake had released. I didn't want to take a chance so I put it on the truck. I figured that as hot as it had gotten I just replaced the rotor, caliper, brake fluid and brake line just to be sure everything was back to normal.
Haven't had a bit of trouble with it since.
The burned one is on the left. It didn't have that gold color before the caliper locked up.

 

Sometimes a tight grip on the brake lever will cause front brake to lock,not saying lol.JMO

 

Old rubber brake hoses can deteriorate and collapse on the inside. This will trap fluid and hold the brake on. If yours are still OE, its definitely time for new ones.