Subject: Re: And now for something completely different....
Author: Ian Adkins
Date: Sep 12, 2001, 9:46 PM
Post ID: 1708218942
Tom,
Thanks!
With all the gasket problems that I have had I look forward to hearing what
you learn from using vinyl as a gasket. I personally am ready to ditch the
standard petcocks that thread into the tank and get some modern ones that
attach onto the fuel line directly.
I was thinking....in plumbing there are "ball" type shut offs where the seal
is made with brass (maybe there is a gasket type material in there?). I am
not advocating using a plumbing shut off for the fule line but was wondering
whether there were petcocks out there that would be suitable for gas?
By the way....are we all still planning to go to the Md Rally? I looked at a
long long range forecast. Thurs-Sat looks good. I'll cross the fingies that
this holds and that it stays nice through the weekend.
Andy...how's it going on the bike?
I keep walking by my bike in the garage. Funny but I have to look at it each
time I walk by. I can hardly wait to get on her and head south...I just hope
you guys let me across the border. In some ways though I doubt the border
crossings will as simple as they were in the past. Too bad.
Thanks again Tom....Ian
-----Original Message-----
From: Tom Bowes <kk-@home.com>
To: Loopfram-@topica.com <Loopfram-@topica.com>
Date: September 12, 2001 10:15 PM
Subject: And now for something completely different....
First of all, congrats to Ian for making the cover of the September MGNOC newsletter. A few thoughts on brake cables and petcock gaskets. The last time we discussed the petcock gasket problem I thought I had it beat by using Viton for the gaskets. I am sorry to say that, alas, once again my efforts have failed. After about a month with the new Viton gaskets I started having fuel starvation problems at speeds over 65 MPH or when going up hills. Subsequent inspection of the gaskets reveals that they have torn in between the holes for the fuel passages and partially blocked the channel in the petcock rotor. This leads me to think that the problem is one of the mechanical strength of the gasket material, rather than the chemical makeup of it. Viton is supposed to nearly impervious to fuels and petroleum based solvents, and therefore should not have been adversely affected. So, "what's the problem?", I ask rhetorically. My guess is that the large amount of spring pressure on the rotor, and the lack of lubricating properties in gasoline simply put too much mechanical strain on the material and cause it to fail. I had an original petcock gasket that I had removed, which I took to the local rubber supplier. The owner looked at it and said that he guessed that it was made out of vinyl, and not one of the fancier sort of elastomers. I asked him if they had any, and he graciously provided me with a sample. At present I am experimenting with a viton gasket, lubricated with silicone grease, in the left petcock, and a vinyl gasket, also lubricated with silicone grease, in the right petcock. So far the vinyl gasket seems to be doing the trick, but I have as yet to get the bike up to freeway speeds to really try it out. Stay tuned, more info to follow. Brake cables.......I had installed a front brake cable (aftermarket) on the bike when I had originally rebuilt it. Gary Cheek took it for a ride and commented on how much firmer the feel was on the brakes for his Eldo. After some comparison he figured out that the original brake cables have a larger core wire, larger jacket, and a different rate of twist to the core wire than do the aftermarket replacements. The net result is that the aftermarket cable appears to be made from the same stuff as the original clutch cable. The core wire is thinner and has a higher rate of twist, thus making it far more stretchy than the original cable. I found an original cable and swapped it for aftermarket one. What a difference! Previously, I could pull the brake lever all the way to the grip with no sensation of the pressure increasing once I reached a certain point. This means that the cable was stretching. With the new cable, the pressure increases linearily with increased pulling force and will not allow the lever to reach the grip. For some of you who are struggling with anemic front brakes this may be a contributing factor. Tom |