Blown another diaphragm

[Lucky_Lou]

Re my previous post "Can you believe this" i showed images of the expanded diaphragm which with less than 200 miles on it had expanded to the point of not being able to refit it....motorwork replaced it foc.The other one has poped at 250 miles again motorworks are replacing foc but claim no one else has had problems. If this happens again its Motobins for me i see they do origonal bing ones ....twice the price but i can do without the greif this problem has given me has anyone else refitted them lately...any problems??or am i just.
Unlucky Lou

[Justin B.]

That is very strange.  The only complaint I've ever heard about the generic "Stromberg" diaphragms has been of their thickness and a change in response due to it.  If they are swelling up then perhaps you have a problem that's allowing gas up in the vacuum chamber?  Are you using any kind of fuel treatment/booster?  I know that if you put rubber parts like this in lacquer thinner they will swell up something fierce.  I remember tearing down a head, tossing valves, keepers, etc., into a can full of thinner, and the next day the valve stem seals were the size of vending machine donuts!

[Bob_Roller]

Just for the sake of conversation, are you wiping down the diaphragms with some sort of chemical before installing them, or using some fuel additive ?

As for rubber expanding, it usually happens after the rubber comes in contact with something it was not intended for .

About the only time I have heard of diaphragms expanding before this, was after a long installation time in the carbs .

[Justin B.]

Bob, the diaphragms that I took out of my '81 R100 (that had sat for years) were torn and very soft but even then didn't look swollen.

[Lucky_Lou]

I use a lead replacement addative its at my workshop i dont know whats in it..its the STP one i will post a list of ingredients tomorrow when i get back from work.
Lou

[Bob_Roller]

Bob, the diaphragms that I took out of my '81 R100 (that had sat for years) were torn and very soft but even then didn't look swollen.

When I replaced my original diaphragms in 1998, it was during the time when MTBE (methyl tertiary butyl ether) was being used for an oxygenating agent in the fuel supply, and within 15 minutes of removal, they swelled up noticeably .

I had taken the carbs apart before that time for cleaning, and never had an issue with them .

[MrRiden]

the valve stem seals were the size of vending machine donuts!

MMM vending machine doughnuts.
Seeing as how they both failed in the same manner I'd expect the replacements to be suspect as well.

[nhmaf]

I have heard of folks on other forums describing that diaphragms expanded after they had been using Sea Foam (fuel additive/cleaner) in a few tanks of fuel, so it is possible that indeed, some volatile chemicals can react with whatever type of rubber these things are made of to cause physical distortion.  Hmmm.  Never thought too seriously about this before now..

[Lucky_Lou]

Ok so i stuck my hand in my deep pocket and was shocked by the differance between a bing diaphragm(motobins origonal) and a generic one from motorworks the image shows a bing one will not support a US quater where as the generic one is unmoved its at least twice as thick as the origonal so must have significant impact on tuneing zoom in for a closer look.
Lou

[nhmaf]

That difference in flexibility would certainly make an impact on the carb's operation !

[MrRiden]

I've heard that the Bing bits are of greater flexibility and thus preferred over the other options [Stromberg?]. You offer the first proof of the difference that I've seen. Thank you for your time and expense. I'll be buying the Bing Part next time it's required.
rich

[R65_Mark]

I’ve been playing with Strombergs since I bought my first Triumph car in the 1970’s (I still have a ’73 GT6Mk3), but only started tinkering with Bings  for the first time when I did a quick strip/clean a few weeks back on the pair fitted to my ’84 R65.  The difference that Lou notes between the diaphragms is very clear when you’ve seen/touched both.  I’d say the Bing ones are much thinner, almost to the extent of being fragile, compared to the Stromberg’s.  Not sure why anyone would think that one would be a direct replacement for the other.  Mark

[Lucky_Lou]

I’ve been playing with Strombergs since I bought my first Triumph car in the 1970’s (I still have a ’73 GT6Mk3), but only started tinkering with Bings  for the first time when I did a quick strip/clean a few weeks back on the pair fitted to my ’84 R65.  The difference that Lou notes between the diaphragms is very clear when you’ve seen/touched both.  I’d say the Bing ones are much thinner, almost to the extent of being fragile, compared to the Stromberg’s.  Not sure why anyone would think that one would be a direct replacement for the other.  Mark

Mark,,,,motorworks do not sell the origonal bing ones??(i always change em as pairs!!) i bought the bings from motobins because of the greif ive been haveing with the generic ones they are twice as much but i will let you know if they were worth the investment i expect to be out on the road next week if i dont have too much work on i feel a test run round pately bridge  comeing up
Lou
ps bear in mind mine is the 1980 model with no springs to assist the diaphragm

[donbmw]

I have only bought the Bing diaphragms and have not had any problems with them. I have changes some that could have been left installed longer. All of the carb problems I have had has been from gas left in the carbs and not riding the bike after alog time of setting.


Don

[R65_Mark]

Mark,,,,motorworks do not sell the origonal bing ones??(i always change em as pairs!!) i bought the bings from motobins because of the greif ive been haveing with the generic ones they are twice as much but i will let you know if they were worth the investment i expect to be out on the road next week if i dont have too much work on i feel a test run round pately bridgecomeing up
Lou
ps bear in mind mine is the 1980 model with no springs to assist the diaphragm  

Lou, We can certainly all learn from your experience here - look at it as taking one for the team.

I am envious of your opportunity to run around Pately Bridge.  Atlanta weather is very 'bike friendly, but the best riding "local" roads are in the North Georgia mountains - at least 90 minutes away for me.  I lived and worked in West Yorkshire for over ten years, and I made several Dales weekend runs on the '71 BSA A65FS I had at the time.  Great memories.  I'll be visiting Fountains Abbey on the way from the Midlands to the Borders in September.  This will be a cultural matrimonial maintenance tour, so it'll be in a rental car and the twisties will be nowhere near as rewarding.

Mark