Topic: Diaphragm Renewal

[Frankenkit]

Found this on an XS11 site...  Given with NO warranty b/c I've not tried it myself, but I will soon, because it might help me save around $100 on a long, ongoing restoration.  I also want to say there's no substitute for "doing it right" and replacing worn or broken parts, but if you just want to jerry rig 'er together until you can do a better repair, this might do it.

Carb Diaphragm Repair
by Tim Trottman

As for my solution for this problem of holes in diaphragms I think I may have a cure for this common problem. First, disassemble the diaphragm from the slide as far down as possible. Second, go to your local NAPA parts store and purchase a can of spray rubber coating. Third, paint your diaphram with the rubber coating with a thin coat on both sides, allowing to dry over night.

Ta da, you have a brand new diaphragm that cost you about 6 bucks.

I have used this stuff many times for lots of applications. It is flexible, as I have sprayed it or should I say painted a peace of paper and after it dried I had a thin durable rubber coating that would not even scape off the paper. I have used it to dampen the front brakes, works great. I have used it for several applications related to exposure to gas and oil and it is resistant to both.

To test its durability I have sprayed the inside of my wheelbarrow to prevent it from rusting and to date I have exposed it to gravel, cement, rocks all the way down to fire wood and it remains untouched. Yet remember, that when applied in a thin coat on the paper, it is just as pliable as a thin piece of rubber.

Given the characteristics of the substance it should work to repair a small hole in a diaphragm.

Vince and all others interested, the stuff you are looking for is at your local NAPA store. The part number is 765-2527 "Plasti Dip Spray-on Heavy Duty Flexible Rubber Coating." Note, this is the part number for black, so if you want a different color, chances are it will be different number. Fantastic stuff!!

Also another good use is to spray your battery terminals, while connected, so as to stop any and all corrosion. And if you are worried about the looks of your carb boots and there cracks give them that factory look again at your next cleaning.

Lots of uses and great stuff.

[nickjtc]

Has anyone tried this stuff? I would imagine that its efficacy is dependant on the size of the hole in the diaphragm...

[Gordon]

I wonder if adding an extra layer of rubber to both sides of the diaphragm, no matter how thin, would just slightly hinder the ability of the carb vacuum to raise the needle.  Possibly enough to cause the bike to run a little lean.  This sounds like a good quick fix when you need it to run now, but I'd still buy new diaphragms and replace them soon.   

[mystic_1]

Well, you're not changing the surface area of the diaphragm or the spring rate of the spring, so I'd guess the effects would be minimal, unless applied thickly enough to affect flexibility of the diaphragm significantly.

That said, I'd go for new ones too.  This definitely goes into my "emergency road fix" file though   Would probably work for those pesky vacuum-driven fuel shut offs on later bikes, too.

mystic_1

[Jay B]

Yamaha wanted $100 for a new diaphram on my 4 wheeler. I found a tiny tear in it up by the slide. I cut a little peice off the red edge of a tire patch and glued it on there using regular vulcanizing cement. Been there 4 years now, works fine.

[snorkelfork]

i tried this a long while back with the suggested material and had poor results though no doubt someone will come along to contradict me. for one, the rubber does seriously affect the suppleness of the diaphragm no matter how thin you apply the material making them stiff and unresponsive. second, eventually you will get a rip in precisely the same place. i must say though that the nappa product suggested is amazing stuff with a lot of potential for other uses, perhaps cracked manifolds or other rubber bits.

i have made numerous attempts to patch the diaphragms on my 350 twins with various materials with no success.

[ohiocaferacer]

Ditto....I tried this technique also.....didnt work.

The rubber spray just is too thick to keep the diaphram usable......good idea....just didnt work for me.

[Frankenkit]

Didn't work for me, either, really.  Think I'll just leave this on here, though, so if someone has the idea, they can search for commendations and read that it's really not as brilliant as they thought.

[tbpmusic]

Well, when the splits or cracks were small, back in The Day we just used a tiny dab of silicon, which generally worked ok. Smear it thin and smooth with your finger, give it a try.
If the diaphragm is in really bad shape, there's not much to be done except replacement.

bill