Is this a crazy idea? Dangerous? Or frugal?

pnedac

pnedac

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So I have some leaking out of the front master cylinder resevoir and I see that it is coming from the cap. I have nice SS lines and I bled the brakes and all (This is on a 77 by the way) and I do not see that I can order JUST the rubber gasket for the cap. I can order it for the 78-94s, but not for before that. What is the harm in getting a piece of rubber and making my own rubber gasket so that the cap does not leak? Has anyone ever done that?

I do not see initially that it would make any difference as it is simply a gasket for the cap. I do not want to spend $75 plus on a whole new setup when I could get by with a custom made rubber gasket that would cost less than a buck.

Any thoughts?

Pnedac
 
I would not think it dangerous unless it does not stop the leak. If that comes to be the case, then you likely have a bigger issue with sealing at the cap, in which case you might be well advised (after trying your gasket idea) to just spend the money on a proper remedy for your front brake.

TC
 
I love it! Thanks. I just wanted to make sure that I am not going out on a limb at the cost of something too crazy here. Simple logic would say that if everything else is working great, then making something on your own will do the trick (as long as it does the trick). I agree though that if it does not stop it I will pony up the dough. In the meantime a quick trip to the hardware store and a little ingenuity will be just fine.

Cheers!

Hell, half the stuff on this bike is after market and it works great!

Thanks again guys.

Pnedac
 
Well, I think (in my very limited experience) that any "compromise" in hydraulic brake integrity would have to occur somewhere below the fluid level. A leak there would reduce pressure, and there goes your lever feel, and your caliper functionality.

But a seep at the cap would mainly only be messy, unless it allowed your fluid to get so low as to admit air to the system and compromise hydraulic pressure. That's how I understand it, anyway. I would not tell you to try anything I would not try myself.

TC
 
Don't know, but I can suggest this: Take a small sample of your gasket material and put it in a bottle with a little brake fluid and watch it for a few days to see if the brake fluid attacks and dissolves the material. If it does, you know it isn't safe. If not, you can be a little more confident.
 
^ good idea there!

Another option would be asking in the classifieds in anyone has a good rubber seal they'd sell you.
 
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Does it have a rubber piece already, but it's just leaking? If so this might fixya. Lift the rubber out of the cap, then lift the piece of sheet metal out. Flatten the corners of the sheet metal where the screws go so that they no longer droop down. With the springiness put back into it, it'll hold the rubber down more evenly.

But if you need the rubber part, it's available from dealers. Any Yamaha dealer will order it for you. Here, parts come in in about a week
1J3-25854-01-00 DIAPHRAGM RESERVOR $12.50
 
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You will need a good and proper fit and seal material to seal hydraulic fluid. It is notoriously difficult to prevent from leaking and remember it's very tough on paint etc. assuming we're talking DOT 3 or 4. I'd go for the new Diaphragm myself of chemical composition
engineered for the specific application. Just being "rubber" (a plethora of highly varied elastomers) is very non specific to use. Blue
 
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Just remember, the diaphram has to seal the fluid in the reservoir, but also breath on the side to atmosphere to allow air to enter between the cap and your diaphram to allow for fluid loss due to pad wear and piston movement (the reason for the bellows) Try your theory but listen to crashcourse first as he's offering good advice, otherwise go the genuine parts and save yourself the disappointment of fluid wrecking your paint
 
Find a truck tire inner tube beside the road. Drag it home to use for rubber gaskets and vibration isolation, all sorts of stuff. This rubber is thick and tough enough for all sorts of jobs and is a fantastic resourse to foster a creative mind. I have gone through several truck inner tubes in the last 40 years. Actually, 50 years! I used inner tube rubber on a sling shot I made as a little kid.

Tom Graham
 
You can get various inner tubes at Harbor Freight and they're real inexpensive. Cheaper than the gas used to find one on the road (unless you see it on your way to work) :) Of course if you can find the rest of the tire you can make Ho Chi Minh sandals.
 
Here where I live there is a great industrial rubber supply company that really knows their stuff. They even ask what kids of fluids you'll be working with and temperature ranges. I get O rings, seals, flat sheet, hoses-- anything made of rubber-- there. Because almost everyone in the place rides and wrenches they always know what I need. And they're lots cheaper than motorcycle shops.

Might be a place like that near you.

PS. While inner-tube might be okay, avoid bicycle inner-tube as most of bicycle inner-tubes are pressed together from scrap. Hence, the reason modern bicycle tires go flat so quickly.
 
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Guys not being rude but what pcoumbe is saying is right , your seal is a diaphram as well so must work to allow air in the top and seal the bottom , the rubber consertiners as fluid level drops otherwise your fluid resovior would vacume causing problems !! if you just use a rubber o-ring or gasket you will prob find it will still leak from the breather ! (NB check breather is not blocked as this causes problems) , if you object spending out on a new diaphram (i do understand , bits aint cheap) have you thought of just using another cylinder the same rating / size off another bike ?? might be a cheaper option and if you get something newer it would be less worn out , just a thought !
 
blim840, xjwmx & pcoumbe observations hit the mark seems to me....

Here's a blow up that shows the parts involved #5 & #6 at least as best I can tell:

http://www.powersportsplus.com/part...-+BRAKE+HOSE+XS650D+-+E+-+E006501-/parts.html

Two parts #5 & #6 may be needed and are available about $ 26 The bellows diaphragm letting air in feature to allow it to follow the fluid level down would pretty much dim the lights on a homemade piece to my mind. Blue
 
650Skull said:
your post does not make sence, What does your reservoir look like............... the info i have on the 77 it has the same reservoir as the 78 and later models. Mikes sells the cap for $37.50 or you could check out [URL="http://www.bikebandit.com/houseofmotorcycles/1979-yamaha-xs650-2f/o/m8268#sch215926"]Bike Banditt[/URL] and they have the DIAPHRAGM RESERVOR for $17.00
Click to expand...

Whats cheap compared to your life. by the time/fuel it takes to mess around trying to find an alternative that may not do the job, in fact it could cause no end of trouble, the links posted, Blue and others, the cost of $17 is nothing in the grand scale of things
 
pnedac hasn't been on in a few days, but he mentioned he thought it was going to be a $75 fix. Now that it's known that the proper fix is less than $20, and the $1 fix just won't work at all, the decision on what to do is obvious.
 

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