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DIAPHRAGM Problems. Suggestions?

  • Thread starter Thread starter spadefoot
  • Start date Start date
S

spadefoot

Guest
I'm in the process of re-working the carbs on my 82 GS650gl. When we took the diaphragms off yesterday, the had some holes worn into them. I've experimented with patching them with some fuel-safe flexible cement, we'll see how that worked today when we take them back apart. I'm considering replacing them, but the only option appears to be buying the OEM part which runs about $110.00 per carb, so $440.00 for replacing these. Is there a way to do the diaphgrams without having to replace the whole valve assembly? It seems like there has to be SOME way to get around spending 400+ just because some little rubber pieces are worn...

I'll try to post an update later today when we get them back apart.
 
Ebay

Ebay

The most practical solution, by far, is to buy a set of carbs from ebay. You're sort of buying a 'pig in a poke' but chances are good you'll get what you need...at a very reasonable price. Also, you'll end up with some other parts that will come in handy at a later date.:-D

There's a pretty decent set on there right now (first item for GS650 parts) with a bid of $25.
 
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I would recommend taking the diaphram as a sample to an industrial
gasket or rubber company who can recommend a thin sheet of rubber
with the same flexible characteristics and dimensions and that is also
impervious to gasoline. I like to improvise and re-engineer something
that can be salvageable and can save you money in the process.

The material must hold under the stress of a vacuum and pressure
environment, and it must last and not tear like in your case. I can
not see you spending $400 for rubber that you will only need as to
repair only one diaphram.

See if you can buy a used Mikini carb similar your style and model,
and then swap only the one diaphram from it. This is the best case
scenario for you.

Goodluck my friend :-D
 
A dyno shop tore the diaphragms on the carbs of a Ninja 250 engine that someone I know had built. They patched them, and then the patches managed to come apart. It ran lean and burned valves on the track (it was a seriously prepped engine, for a racebike).

I wouldn't recommend patching them.
 
Trying to repair them is a lost cause. You might get them sorted for a short time but it won't last. The only solution is to replace them. I doubt that you will be able to buy a suitable material to fab new ones so going the route of used might be the cheapest option.

As mentioned spare carbs won't go amiss as you will have additional parts should you ever need them.

Let us know what you end up doing.

Good luck on the preoject.

Cheers,
Spyug
 
I would not patch them either. Too much flexible stress upon those
rubber diaphrams. Too much trouble to begin with.

If it is just a small minor slit or needle poke, then bicycle innertube
rubber cement comes into view as an idea. But again, the gas would
probably attack it and break it down, creating contaminated sticky gas that may clog your jets.

See if you can melt, fuse, and seal the rubber hole/tear with a soldering iron with just the heat of the iron. I'm not sure if it could be done, but
you have nothing to lose. If it can melt, make the surface an even
flow so that it is strong in the patch area.

:-D\\:D/
 
None of the holes were big, just some worn spots. We used a product called Seal-All, which seems to be similar to innertube repair adhesive, but is advertised as gas and oil safe. It seems to be flexible when dried, and (so far, anyway) they seem to be holding pressure.

On the subject of finding a spare set of carbs: Does anyone know of any other bikes that use these same carbs? I figure I'll have more luck on EBay if I know what other bikes are compatable.

Thanks for the ideas!
 
Miukuni makes many carbs for many Japanese brand of bikes. You
should have no trouble cross-referencing your carbs to other makes
and models.

The bodies are the same, and maybe the linkage for the throttle
and and choke may be different dependant on the application.
They all work in teh same principle - mixing the air with the gas
in a myst for atomation.

I feel this diaphram is very popular and could be universal for 30-32
-34-36-38-40mm carbs. I would imagine just the throats are different
other other than the various jets and the bowl size.

:-D\\:D/







uki and Honda.
 
Well darn, out of the running for a bit.

Well darn, out of the running for a bit.

Well, one of the main jets broke when were putting it back in. It actually just snapped in half along the threads. Also one of the throttle bodies has some messed up threads.

It would apprear that a previous owner really mangled these things.

I'm looking for a set of carbs if anyone knows of a set. I found one on ebay, but I haven't gotten an answer back from the seller yet.

AAAARRRRRGH!
 
Here's something I have tried and was successful with for short term.
I found some holes in my diaphrams, and patched them with the spray can version of Plasti-seal. (It's the stuff you coat tool handels with).
I patched my diaphrams, and put the carbs back in service. I ordered new diaphrams
and received them about a month later ( It was a money thing.)
When I removed the "repaired" diaphrams, they still looked great and had no problems at the repair area.
Comments?
 
That is always the best way - and the cheapest way to go. Buy another carb set, and extract parts from it. or rebuild and use it. It will be just
like new !! Used is very reasonable @ $50-$100 on Ebay.

New from the dealer is at least $1000 if you can find them.

:-D\\:D/
 
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