Front master cylinder leak...still

[PA Chopper]

Hey guys,
I posted a while ago about my front master cylinder leaking. At the time I took off the cover and gasket, wiped everything dry, sucked out a bit of fluid and reassembled. It was okay for awhile and now it is leaking again. I just removed the cover and gasket again and was about to wipe and dry again but I noticed that there is a tiny pin hole in the bottom of the resevoir. Obviously there is the large hole where the fluid goes thru to the line but I see a smaller hole about the size of pencil lead right by one of the stocks where the screw goes in for the cover. I wanted to grab a picture to post but my camera batteries need charged. Does anyone know if this is normal? I'm guessing there shouldn't be another tiny hole in the bottom of the master cylinder. I know there is a vent hole in the lid but this is at the bottom of the resevoir.

 

[KaptinAmerika]

Where does the fluid look like it is leaking from? Is it coming from maround the screws, seeping through around the edge of the gasket?

 

[PA Chopper]

Its kind of hard to tell for sure when riding since it blows all over the place but it seems it is coming out the vent hole, around the screws and between the cover and gasket. It is not overfilled. It's funny, I went for a ride yesterday, came home and wiped off the fluid. This morning I went to look and there was fluid all over the front of the master cylinder. Must have came out of the vent hole and ran down. This is driving me nuts. When I'm riding the fluid actually blows back on my arm at times. This damn DOT 5 blows everywhere.

 

[Trainguy]

Mine leaked from the getgo. The small vent hole is normal. Drop your fluid level to about 2/3 full, as a added measure i put small fiber washers on the hold down screws.:up: Clean all the surfaces and put back together. That worked for me.:2thumbs:

 

[KaptinAmerika]

Mine leaked from the getgo. The small vent hole is normal. Drop your fluid level to about 2/3 full, as a added measure i put small fiber washers on the hold down screws.:up: Clean all the surfaces and put back together. That worked for me.:2thumbs:

Man that ain't right. Have you taken a really close look at your gasket? If its been overtorqued already then the edge of the gasket will be trashed. I would definitely try Trainguy's fiber washer idea if the gasket really is OK. The vent hole in the cap simply allows the gasket to flex inside the housing. If you have fluid coming out of the vent hole then there is definitely something wrong with the gasket. Maybe just try a new gasket there not that expensive.

 

[Top1371]

I'm in the same boat right now PA, Gonna hit up the stealer and see If they have a gasket or a rebuild kit on Monday. Really worried about this shit getting on my paint., and I want to get it fixed before next Saturday. Don't wanna have to ride the shadow next weekend.

 

[PA Chopper]

Hey guys..I see there is another member on here with a leaking front master cylinder so I just wanted to update my post. I got another chrome master cylinder from my dealer, installed it and it has been working fine so far. I think the lid on the original one my have been warped. I laid it on a flat piece of metal and is was not truely flat. Don't know if that was the problem. I did throughly flush out the line and caliper and switched brake fluid to Motul RBF 600. No leaks so far and it seems the pads grab a bit better. Since I got the bike though I have noticed that the pull on the lever isn't that good. The lever has to travel a further distance than on my Harley before the pads start grabbing. Is this a Big Dog thing or do I have a problem? The brakes work but I got to pull pretty far to haul her down. My Harley is a two finger pull and the lever barely moves.

 

[KaptinAmerika]

Hey guys..I see there is another member on here with a leaking front master cylinder so I just wanted to update my post. I got another chrome master cylinder from my dealer, installed it and it has been working fine so far. I think the lid on the original one my have been warped. I laid it on a flat piece of metal and is was not truely flat. Don't know if that was the problem. I did throughly flush out the line and caliper and switched brake fluid to Motul RBF 600. No leaks so far and it seems the pads grab a bit better. Since I got the bike though I have noticed that the pull on the lever isn't that good. The lever has to travel a further distance than on my Harley before the pads start grabbing. Is this a Big Dog thing or do I have a problem? The brakes work but I got to pull pretty far to haul her down. My Harley is a two finger pull and the lever barely moves.

Better try bleeding again. If you have to pull that far then you have air in the line. Try pumping the lever a bunch of times and see if if it tightens up at all. If it does then you have air in your line. You might want to try injecting fluid with a large syringe from the caliper side. The PM calipers tend to want to hold air and they will bleed better from the caliper side.

 

[PA Chopper]

Kaptin,
I actually filled the master cylinder by running the fluid through the caliper. I took a large syringe without the plunger and tubing and rigged up an IV pole style setup. I poured the fluid into the syringe and let it flow down the tubing to get the air out. Then I hooked it up to the bleeder and let it run thru the caliper, up the brake line and into the master cylinder until it filled it up. Alot of air came out that way but it may not have been enough.
How is the lever on your bike? Does it have pressure right away or does it move some before getting pressure? Mine doesn't pull the whole way to the grip but it does go about a 1/4 inch before getting pressure.

 

[KaptinAmerika]

I would bleed it again. Its not always a simple matter of doing it one way. Try bleeding it the old fashion way as well. I have "Custom Cycle Controls" "Climax" Controls but hydraulic brakes are hydrauic brakes. My caliper activation is almost instantaneous when I start pulling. When I first got it back from the shop that put them on I had to pull the lever a good inich before activation. I bled them again and pulled a bunch of air out of the system and they have been fine ever since.

 

[angel07]

I faced same kind of problem.
But after a repair(I wiped it till it got dried and made some rearrangement), it's been great!

 

[chrisestel]

Im dealing with the same problem for a while now. Just ordered a new hand control because the rebuild kit didnt work for me, I guess the bore is just worn out and the fluid is getting past the cup seal, o-ring, and boot.. We'll see how it goes when the new master cylinder body comes in! Good luck with your fix!

 

[Ray]

Same kind of issue here when I went through my brakes front and back. The front was the pain, and no matter how much I bled it I knew there was still air in it. Red at R&B told me to bring it over and he would show me what I was not doing.

He took the cover off and pumped it several times, then he just thumped the reservior a few times with his finger. He did this a few times and I saw a few tiny bubbles of air come up, two or three at the most. He kinda smiled, wiped it off, put the cover back on. That fixed it. He said not to over tighten too!!!
There was a tiny bit of air trapped that made all the difference.

Ray

 

[jimizee028]

If you are using the CORRECT type of brake fluids for our brake systems,I believe its DOT5,it will not affect paint........unlike brake fluid that we use in our trucks and cars....

 

[Top1371]

If you are using the CORRECT type of brake fluids for our brake systems,I believe its DOT5,it will not affect paint........unlike brake fluid that we use in our trucks and cars....

Tell that to Can-Dog1.

 

[WideOpenRider]

Fiber Washers

Mine leaked from the getgo. The small vent hole is normal. Drop your fluid level to about 2/3 full, as a added measure i put small fiber washers on the hold down screws.:up: Clean all the surfaces and put back together. That worked for me.:2thumbs:

Trainguy, where exactly did you insert the fiber washers into the assembly and was it effective? These gaskets no longer exist and I have leakage out the cover's screw holes. Thank you in advance for your help!