Wrinkled carb diaphragm?
 

These look almost melted. In one spot, two folds really have melted together. What happened here? It seems to still work okay... (that is, I believe all the carb problems have other causes) is it worth replacing?

http://www.skippii.com/pics/tech/diaphragm.jpghttp://www.skippii.com/pics/tech/diaphragm2.jpg

Why a cause? Not uncommon with age, we just throw them in the garbage and install new ones.:wink:

Ethanol in gasoline.

Maybe the Ethanol but I have seen that on many older carbs in Canada and we don't have corn juice in the gas most times. I can almost bet that's what I'd find in the little chain saw that's getting hard to start, not CVs but diaphragms and looking like that all too common.:eek1

Interesting anyway, I have a set of CVs from an american bike here I don't think have ever been opened. If I can just unseize the screws after 25 years of corrosion, I'll look.:rofl

Just to say that things like that happened well before the corn juice in the gasoline.....and the Internet. Maybe they happen faster now, that I wouldn't know. What I do know is that my 90 R100GS, Canadian specs never liked American gas in general even 20 years ago before the corn juice.Pinged like crazy and yes had to replace the diaphragms at one point, that's just a wear part to some of us.

I'll add a diaphragm to the carb parts/fuel lines in my straight Ethanol test jar. Haven't looked at that for a couple months.:D

:huh That'd be $400 if I had to do that.

They are implausibly expensive. Another option is to get them from a salvage place, but those would be just as old and who knows how long they would last. If they aren't torn I'd run them.

:eek1 Better check some prices before we yank the carbs out of that Honda Sabre. Labour alone on that would closer to a thousand at a shop.:rofl

They are only like $30.00 each on an old airhead.:wink:

Is Skippii finding corrosion on the mating surfaces? There seem to be some attacking the rubber on the sealing edge. Air leaks may be part of the problem here.:ear

It looks to me like the slides were left in the last time the carbs were dunked in the Bucket of Doom. Carb cleaner+rubber bits=$$$.

Now fess up! Have you ever squirted a shot of ether in there?

Yep, just what I was thinking.

This sort of thing happens over on the vintage forums all the time -- instead of a proper complete disassembly/rebuild, people try to spritz carb cleaner all over the place and call that a rebuild.

One drop of spray carb cleaner can easily ruin a rubber diaphragm.


And, of course, nothing but metal should go into the highly caustic can of carb dip. If that's what happened to this diaphragm, I don't think there would be any rubber left.


Someone else mentioned ether spray, too -- I'm not sure that stuff will melt this type of rubber, but it's certainly not good for anything.

if that diaphragm is from a CVK40 Kehin, go to the Harley shop.... really. it's half the price that the Kawi shop wants for the same part. I can't find the Hardly part number, but I'll look deeper.

Most of the old ones look like that. Use em.

I have no knowledge of what the previous owners did, but I've never cleaned the carbs before.
Well, I do know that someone at one point changed the main jet from a 125 to a 140, and that I now get 27mpg instead of the 50+ that everyone else seems to get.
This is from the 2-carb, single diaphragm, single cylinder 1986 Yamaha XT350.
I figured it was probably just age, but wasn't sure.
I've seen people blame ethanol in gas for so many things on this site that I don't know what parts to take seriously anymore, but thought this might be a reasonable circumstance.

No, I've read too many stories to want to mess with that stuff.

Nope, it's from a Teikei dual carb thing (one carb for low and midrange, a separate one for high end). Parts/jets are really fun to locate for these.

actually, I agree with concours, if they aren't torn & no pin holes, etc they will still work.

My other computer crashed inwhich I have the address etc for a company in the eastern part of the US that puts new ones on the old piston-about $20 last I looked.Go to the yamaha XT site maybe someone there that previously used them will ring you.