Beware: eBay Master Cylinders

[fR3ZNO]

Just wanted to make this thread to give others a heads up regarding master cylinders.

Few weeks ago, I was shopping around for a MC or rebuild kit. Naturally, shopped around on eBay a bit and thought, hey a new MC would be great!

So, I bought this: Don't mind the Suzuki fitment, the eBay seller who sells this lists fitment for pretty much every bike imaginable.

Went ahead and installed this after rebuilding my caliper, I tried and tried to bleed the damn thing of air. No matter what I tried, I could not remove the air. Starting thinking the problem was with the caliper, since the MC was new. Even tried the included rebuild kit that came with the new MC in my original Yamaha MC. Still didn't work. So I assumed the problem was with the caliper. After doing some troubleshooting, got stuck and scratched my head.

Stopped by the local pick and pull that usually has a few motorcycles and grabbed a MC from a Kawasaki (GS?) that still had fluid in it and good handle pressure.

Put it on my bike as a last ditch effort, before taking the caliper apart, and guess what? The damn thing bleed like it was supposed to! It took me a good five minutes to completely bleed it with a good MC; compared to the 15-30 minutes of fruitless bleeding even with the "new MC".

Long story, short. Don't be tempted by the new eBay MC... just pick up a good used one or rebuild your current one. I wish I had... the rebuild kit would have been worth the $25-30.

 

[Wolfe_11B]

It may be fine. It's hard to get a dry MC to bleed properly.

 

[fR3ZNO]

Maybe. All I know is I bled the heck out of that thing. I went through like 2 quarts of brake fluid. I tried a vacuum bleeder as well. I stuck the end of the brake line into the reservoir and pumped the air out (like a bench bleed for a car MC) then hooked the line up to the caliper, it still had some air and next to no handle pressure.

 

[Edward]

I bought an ebay MC as well, I had a hell of a time bleeding it the first time. I think I spent over an hour doing it. I was positive I had a defective unit at first.

First I filled the reservoir and bled the caliper, but there was zero lever feel. Every time I pulled the lever, I could see a small bubble come out of the master cylinder into the reservoir. I assumed that there was air in the line up top or in the cylinder, so I did that over and over, pulling the lever, gently tapping the master cylinder and wiggling the lines. Eventually the lever got firm and it felt great.

This was my first time ever swapping out a master cylinder, so I don't know if better/more expensive units bleed better/faster.

 

[levdir]

My experience with a third-party eBay MC was about the same as yours. Took a bit of extra work compared to the stock MC with a faulty piston seal I replaced, but it's given me no trouble since then. I brake so long that I've barely used my front brake as it is, but a little bit of extra work bleeding wasn't much of an issue.

The real problem I had with my eBay unit was that the hose running between the reservoir and the piston assembly tended to sweat brake fluid so I ended up rebleeding my brakes after getting them feeling good because I had to replace it with heavier, less permeable line.

 

[fR3ZNO]

Interesting responses. Maybe I got a dud. Like I said, I tried bleeding the heck out of it. I even used a vacuum bleeder and it just kept pulling air air air and more air from the bleeder. I've bled a mc on a car before so I figured it was a similar process.

 

[levdir]

I kind of assume that the odds of getting a dud unit from Chinese Manufacturer X are higher than buying NOS factory parts or whatever fancy Italian aftermarket maker you care to name, but the difference in price is worth it for me. Sucks that it gave you so much trouble though.