I thought I'd post this more for the information of others than any other reason. A while back I mentioned that my front brake lever wouldn't reset the light all the time. I put a set screw in the switch and it solved the problem for a little while. However, whenever it was cold I started having issues with a soft brake lever and slow return.

I ended up buying a new front brake line as the old one was bent kinda funky from clearly a few years of handlebar swaps (I bought my 1998 FXSTC in 2012) and I bought a front master cylinder rebuild kit.

Last summer I had tried flushing the brake fluid, but it didn't solve the problem.

After pulling the front master cylinder apart it was apparent what the problem was. The thing looked like a sewer, and was full of sticky gunk and grease-like gunk that was preventing the piston from moving smoothly. I pulled the piston and o-rings out and used a generous amount of carb cleaner and some pistol cleaning brushes (the soft ones) to clean the bore of the master cylinder to the best of my ability. I then did a final cleaning using DOT5 brake fluid to get rid of any contaminants from the carb cleaner.

I re-assembled the master cylinder with the 15 dollar rebuild kit from Drag Specialties. The only difficult part was getting that outer wiper ring on. I ended up needing to use a screw driver to carefully push it in, and quite frankly I'm not stoked with how clean it went back in, but it seems to be working just fine.

After putting it all back together with the new stainless line I went to bleed it.

A note on bleeding the front brakes... I have found I need to take the front master cylinder off and rotate it around on all axis while pulling the lever and watching for bubbles to come out to get all the air out, no matter how much I pump them air seems to stay trapped in the master. This seems to work pretty well.

Now that it is all back together, the brakes feel brand new and the lever instantly fully returns.

So hopefully anyone having issues with their brake levers returning stumbles across this thread and is able to fix it.

Mike

 

About half way through your post I was going to suggest rebuilding the master cylinder, and that someone probably put DoT 3 or 4 or 5.1 fluid in it at some point. Glad you got it sorted out.

 

Although I've never had an issue with the fronts I appreciate the info. The rears are another story though. I don't care much for the factory cover on some of the master cylinders, 98 down. They are cheap pot metal and tend to warp allowing moisture in and we all know what happens then. I have straightened the cover a couple of times now but would like to know it anyone has a replacement for it...

 

Mike, I agree with Dr H, that your poor bike has suffered the indignity of someone mixing fluid types over the years. I know, having done it myself (I bought my bike new in 1990). Left too long the bores of the master cylinders can erode and become useless. Having done your front brake I heartily recommend you now do the rear! Whoever serviced the front will also have done the same to the rear brake.

 

Reverse bleed them with a syringe, works every time.

 

I reverse bled them last time with an oil can, same issue, although it may have been because there was so much gunk around the plunger. It literally looked like someone dipped it in grease and rolled it around in the mud.

It did seem like there was some minor pitting in the bore but they are working fine now. If not, I'll throw some polshing compound on a soft bore brush and throw it in a drill.

I do now want to do the rear, god knows how bad it is.

Mike

 

I don't even try to bleed the front brakes with the vacuum. I always go straight to the reverse bleed. I once worked for two days trying to bleed the front brakes on a softail. Went to the reverse bleed and it was done in 30 seconds.