In another thread on fuel taps, I noticed that Brit Gasket has an upgrade kit that uses Viton o-rings and a new spindle to replace the original cork seal. I understand that Steve, the creator of the kit is a member here and I want to state up front that I'm simply asking for input here, not trying to disparage the product in any way. The change to o-rings seems like a good modern approach with one exception. The o-ring on on end is required to pass thru the perdendicular bore that supplies fuel from the tank. As a rule, o-rings are intended to be fully captured and are not meant to have portions of them unsupported as would be the case when you open the petcock on this design. A portion of the o-ring passes by that open area of the fuel supply bore and I'm sure partially extrudes into the bore. This means it is possible to shear of a bit of the ring in that area each time you open and close the tap. The only way to possibly reduce the risk would be to twist it as you pull it, but that is not possible with the locking screw.
So my question is, has anyone found this mod to leak fuel into the float bowls in the closed position after some time in service? My guess is you don't know it is happening because the other o-ring never sees this condition and functions properly keeping fuel from leaking out the tap knob area when in the closed position. As long as your float valve works, all is well.
Again, not trying to dump on this design. But my understanding of o-ring applications tells me the design is flawed and before I modify my taps with this design, I'd like to see if anyone has experienced leakage past the o-ring in the closed position into the float bowls. You might have to pull the hose off the carb to check.
I am using a similar product, but not the Britgasket product. So far, no problems. But, I know some say they have had problems.
Long before the corks got retired, I had started lightly honing the inside of the petcock bore to help cork life. I used a small rod with like 320 grit paper attached and "flapped" the bore of the petcock. Kind of crude, but it gets rid of sharp edges and accumulated crud Cork life improved. And so far, the o-ring have been inside that bike for about 1½ years now with no issues.
Down side, they are a bit stiffer to pull on/off, especially on the reserve side that gets much less use. Upside, when they do leak, simple matter to get new o-rings.
Hi Rob. I have converted my petcocks to use the viton o-rings last year. What I found is that the new spindles with the viton o-rings were very tight and difficult to move and after a couple of uses, fuel would not be completly cut off from the carbs. Once the fuel level in the tank was low, I removed the spindles and examined the 0-rings. What I found was as you said, nicks in the o-ring. So it is definately caused by the o-ring passing the perpendicular bore that supplies the fuel. I have gone through 2 dozen o-rings to date, and have another dozen as spares. This month I have sanded the bore using 400 grit sandpaper and would like to figure out a way to smooth out the opening of the perpendicular bore so as to minimize the tearing of the o-ring. In the meantime, I will rock the spindle as I am opening or closing the petcock and hope that there are no more tear outs.
1969 BSA Lightning
Re: Ewart's fuel tap upgrade kits
#368129 04/14/1112:42 am04/14/1112:42 am
I used a bobby pin in a dremel thru the perpendicular bore to pick up a bit of sandpaper to chamfer the area where the bores meet to make it a bit easier on corks. But I eventually gave up and went to different petcocks.
I have had constant torn o-rings with the o-ring style shut offs. Sometimes the o-ring is so torn that I have a very difficult time getting the spindle out to replace the torn o-ring. For my machine they have not been a panacea.
1967 BSA Wasp 1967 BSA Hornet (West Coast Model) 1967 BSA Hornet (East Coast Model) 1968 BSA Firebird Scrambler 1968 BSA Spitfire Mark IV
Re: Ewart's fuel tap upgrade kits
[Re: Gary E]
#368186 04/14/113:01 pm04/14/113:01 pm
"O" rings sliding over an opening is problematic. I was surprised how well my cork Ewarts worked after a dunk into boiling water. They do not leak at all. Whoever came up with that idea deserves an ice cold Yengling.
Your experiences with this mod confirms my suspicions. It's an improper application of o-rings.
Chamfering the perpendicular port opening might help, but won't cure the problem. The o-ring is always going to drag behind its groove to some extent meaning it will always get pinched when you close the tap.
For this type of valve design, I don't see a better way to seal the flow side of the valve other than perhaps a polymer replacement for the cork seal. I'm not aware of anything out there regardless of the application.
Glad I asked. I'll be sticking with the cork design.
I shagged about with these incessently a few years back....wasted absolute hours untill it became a matter of principle to fix the sods!....i became obsessive...it wasnt going to beat me!.
Tree bark (cork) IMO is the way to go....spend ages trying diffrent diameters ect and finaly discovered the exact method of sizing them...the trick is make the corks about 12mm diameter (smooth ground finish). They also need plenty of compression lenghways and on the spindle, fit them to the spindle and then boil them up and shove them into a drilled peice of alloy or steel drilled and reamed, for smooth finish, at 9.5 (3/8") , with a huge chamfer to get them started and let them settle in there a few days then they wont be so hard to fit to the taps. rub soap on the "set to size " corks and wobble them into the tap.
the biggest prob I found was the cork tearing as it passed the spindel lock screw burrs...the diameter of the body is some idiotic 64th inch size (23/64", 9.15mm) and i was lucky to borrow a reamer the right size (what were the chances).
anyhow reamed the burrs out , replaced the corks (Mk 15 attempt) and the ones there now have been fine for 3 years.
there are something like 9 diffrent grades of cork (true) and the result you get depends on the grade of cork you use ...I got hold of some "extra" grade which is apparently 2nd best you can get....the corks i tried from the home brew shop were just useless.
I never knew tree bark was such a science
BESIDES TREE BARK IS ORIGINAL!
"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Let's all gather hands...someone strike up a chord:
WEEEEE BELIEEEEEVE IN BAAAAARK!
As long as they're in regular use, I've not had a lick or trouble with the bark petcocks. Haven't boiled the ones in the Royal Star in nearly two years. Yes, if they sit for more than a couple of months, they'll shrink...but geez, how hard is to put the plunger in an old tin can and pour some boiling water on it? Smear some soap on and, go, go, GO!
WEEEEE BELIEEEEEVE IN BAAAAARK!
A smattering: '53 Gold Flash '67 Royal Star '71 Rickman Metisse '40 Silver Star '37 Rudge Special sixtyseventy Lightboltrocket road racer...and many more.
Re: Ewart's fuel tap upgrade kits
#368260 04/15/1112:27 am04/15/1112:27 am
I just changed out a cork this evening. I counted, and I have 11 of these petcocks in service. Eleven of em holding back gasoline as we speak. I always wanted to try Steve's kit in some of them, but the parts budget never seemed to allow it.
Not wanting to sidetrack this thread too much, but here's what I've been doing: First of all, I have a little bag of the ready made replacement corks. I reject probably half of them, but have been able to get them from various dealers for not much money.
Second, I haven't drove one of those little spindles out of the knob since norbsa from Michigan mentioned how he'd been just slitting one side of the cork and carefully installing it that way. This has been working just fine for me........soak the cork in hot water before trying to work it onto the spindle.
Guys, here's what I like about this site. We have a bunch of grown men enthusiastically debating the merits as well as the problems of a 50 year old gas line tap design. Normal people, the opposite gender in particular, would label us eccentric and weird but it sure is fun to spend afternoons in the solitude of my shop, tinkering with these BSA issues.
I agree, Mike. It's being able to talk about silly stuff like this with other of similar ilk that makes everyone smarter and happier at the same time. I think a lot of bikers from the pre-internet days were grumpy because they had nobody else to talk to about bikes. Discussions like this make the world a happier place.
As for the grown men comment, not sure that applies across the board. I know of at least one gray haired kid involved here.
I thihk the property that cork has that other man made elastomers don't is the inability for portions of it to extrude away from the main form. I think a Viton or similar barrel shaped seal would just extrude up into the bore when the tap is closed and start to wear every time it is opened until it starts to leak.
I've tried to machine cork to replace cork stoppers on fancy wine bottle stoppers. I've used old wine corks for the process. Drilling is difficult at best. The bit tends to chew the cork more than cut it. I would think that a small stone on an arbor, like Dremel tools, would work. Although the stench of burning cork might not make others in the house happy.
Funny you should mention wine corks, because I too now look at them with a more curious eye. I opened a bottle the other day that has a modern, man-made cork. The cork is a high density foam with a skin on the outside. I would suspect it comes in long rods and it just snipped to length by the corking machine. The skin would probably preclude the material from extruding into the bore in the closed position. Unfortuately, the cork is not the correct diameter. And the question of compatability with fuels has to be answered as well.
Not sure what the market is for replacement corks on BSA fuel taps. Probably not worth the cost of making a die to produce a run of corks made in a similar fashion to the wine cork. Plus, I'm not sure how the end of the "skin" would handle passing by the edge of the bore. It might catch and eventually tear. But then again, the real cork has a similar risk and apparently it is not a problem.
Well, as it turns out, I'm in cork Hell today. I drained my tank to do some other stuff and after a couple of weeks the corks dried out. I never thought it would happen that quickly. So yesterday I boiled them and one puffed up nicely while the other did not. So I tried acetone which seemed to help. My assumption was perhapes a varnish had formed that was preventing the corks from sucking up the boiling water. It got better, but was still loose.
So last night I soaked it in a cup of gas. This morning I put it in and it was quite tight. So I installed them both and of course the one that was snug from boiling leaked like a sieve. Fortunately, I did not fill the tank. Drained the tank again and am now soaking that one in gas. Will let it soak for 4 hours and so and see what happens.
I boiled the one that I soaked last night several times and even put it in an ultrasonic cleaner with hot water and it would not swell. Only the gas brought it back to life.
It's a good thing I'm going thru this annoyance because I found that the banjo fitting on the carb was loose as was the fitting it bolts to that screws into the carb. I had a fuel gusher from the carb before I initially drained the tank and thought the float had stuck or had dirt in the needle valve. Now I suspect that it was the banjo fitting and I must've tightened it when I put pressure on it with the screw driver to remove the fuel lines.
I'll let you know if the gas soak does the trick. If not, I'll probably go with a modern replacment due to the safety factor and the PIA factor. I can always put Ewarts back on if I decide to show the bike.
I may try to make my own corks. I'm thinking Dremel mounted on my lathe will do the trick. Glad the proper working dimensions were posted here. Thanks for that.
When rebuilding SU carbs I use to soak the choke corks in oil overnight. I even warmed the oil but never to a boil. I am going to try this on a set of cork petcocks to see what happens. JRC and Rabers sell new corks
While soaking my leaking cork tap, I decided to try and make a replacement cork seal from a wine cork. I had several in the drawer and picked one of a quality that matched the cork on my taps. I actually have an even better cork that is perfectly smooth with no voids or holes that I saved in case I was successful. Well, I was.
I put the wine cork in a collet in my lathe and put a sanding drum in my Dremel. For first try I decided to just rest my hand on the compound to keep the sides of the cork parallel. Took about 1 minute to get the cork to diameter and it is smooth as can be. I measured the brass stem on one tap where it comes out thru the knob. Not sure that is correct, but it was all I had. Measures just under 1/8". I did not have a small mounted stone for my Dremel that small, so I used a small burr. Ran the lathe at full speed with the burr in a a chuck in the tailpiece of the lathe. Made a lovely 1/16 hole. Here is a pic of the finished product along with the burr I used. The first try turned out to be too small. I eyeballed it and when I measured it, I was exactly the same size as my leaky cork after it swelled up. Need to make another, but I'm thinking this one might swell up once it gets wet. Been sitting in the drawer all winter.
Total time about 10 minutes. I parted off the cork to length with a disposible scalpel. Nice to have a wife in the medical field.
If my leaking cork does not stop leaking, I will try the split method mentioned here to install my new cork. I was also thinking about turning a new spindle and knob from brass and threaded it so it would be easy to disassemble to replace the cork and also allow some experimentation for size and maybe other materials down the road.
Actually it was a gorgeous day today, Boomer. Which is why this was so annoying. I just put plated on the bike yesterday and wanted to take her for the maiden ride. Leaking fuel taps killed those plans.
But all's well that ends well. I made two new cork seals from an old wine cork. Probably about 20 minutes effort to make. I used the dimension here of 12mm for the OD of the cork. I made the rest of the cork to match my fuel tap plunger dimensions. It appears to be an aftermarket tap because it is all metric. The tap body has a nice chamfered lead to start the cork so with some careful nudging and a little liquid soap, they were in place. The best part is NO STINKIN' LEAKS!!!!
Here's two pics, one of the finished seals and the burr I used to make the center hole and the other is the disassembled knob/plunger with a new seal ready to be installed. Thought those who have never seen one apart would like to see it for reference. Very easy to disassemble. 1/8" punch, soft jaws to rest the knob in the vise, tap, tap and apart.
We'll see how they hold up. Dremel with sanding disc was used to make the OD while the cork turned at max speed in my lathe. I then used a fine cut flat file to smooth and bring the seal to final size. I put a very slight chamfer on one end to make it easier to start the cork into the tap body.
Did get to take the bike out for my first ride on her. Ran like a raped ape. Starts on the first kick. Idles smooth. No leaks... and a hoot to ride.