TOPIC:

The top of the diaphragms have vertical cracks where they are secured by the top chamber covers. 
They are for a 1982 GPZ 550.  I have done some pretty hard searching but looks like they are not available.

Anyone have any long-term fixes?  Plasti-dip or a specific RTV that might work?

These older bikes sure can be fun!   

eBay item number:234542320217

Would these work?

wrote:

eBay item number:234542320217

Would these work?



 

Does not look correct unfortunately.  Most of the replacement rubber seemed to be all round with a small point, mine are unique with larger pointed area.
Partzilla part number for the whole valve is 16126-1047.  I see some companies offering replacement rubber but not for these unique carbs. 

 
 

From an old topic on another forum someone used Gorilla glue or its equivalent. Here's the pertinent paragraph:

After reading some industrial adhesives literature, I came across a family of adhesives that include regular super glue & polyurethane adhesives. You may know the polyurethane adhesives under Gorilla Glue or Elmer's Probond. These guys have di-isocyanates in them and can be particularly nasty, but cyanoacrylates and di-isocyanates are one of the only suitable bonding materials for nitrile rubber, or even hydrogenated n butyl rubbers (the green o rings used in r134 ac systems). .... So gorilla glue is your best bet. Superglue cures too stiff, and will degrade over time with humidity. The gorilla glue, being a polyurethane and using the chemicals it does to react with the bonded surfaces, won't let go even when covered with gasoline or carb cleaner. It remains somewhat flexible, but of course is much stiffer than your diaphragm which is just a nitrile rubber coated cloth. You can apply it thinly over tears and cracks and holes and it's not going to let go. END.

TK26 info.  In case you aren't aware:  Here's a link to the loudhvx motorcycle stuff page which has lots of KZ550 info.
scroll down for the TK26 link. I did not see anything about the diaphragms.
s3.amazonaws.com/gpzweb/index.html#home

I recently fixed a small tear in a diaphragm using PPG PS890.  This is a polysulfide material, designed as a fuel tank sealer for aircraft.  It's a two-part catalyzed material that sticks well to the existing material.  If the cracks you mention are up near the edge of the top, and don't extend down very far into the working area of the diaphragm, that stuff may work.  

It's quite expensive, and has a short shelf life (6 months, or something like that).  We throw a lot of it away due to expired shelf life.  After expiring, it's still good for a month or two, before it gets hard inside the tubes.  There is a chance that I can get my hands on a tube of recently expired material for you to try.  That will save money.  Message me if you want to look around for some...

I did find this site but not sure how they mount/install nor if they are well known and would actually send them to me, never tried to get anything outside of the USA.
nrp-carbs.co.uk/shop/index.php?route=com...search&brand=GPZ550H
It would be nice to know I had a backup in case trying to repair them did not work out.

wrote:

I recently fixed a small tear in a diaphragm using PPG PS890.  This is a polysulfide material, designed as a fuel tank sealer for aircraft.  It's a two-part catalyzed material that sticks well to the existing material.  If the cracks you mention are up near the edge of the top, and don't extend down very far into the working area of the diaphragm, that stuff may work.  

It's quite expensive, and has a short shelf life (6 months, or something like that).  We throw a lot of it away due to expired shelf life.  After expiring, it's still good for a month or two, before it gets hard inside the tubes.  There is a chance that I can get my hands on a tube of recently expired material for you to try.  That will save money.  Message me if you want to look around for some...

When I try to PM I just get an error message.  Also signed up for email notices for subject posts but I have never seen one.

Some searching on this site and others seemed to suggest Plastidip or Honda/Yamabond being good options.  I suppose there is no consensus? 
Thank you for the help!!

By GpzGreen:  I did find this site but not sure how they mount/install ...

JBM Industries has a how-to for installing CV diaphragms.  There's a video and various pages w pics & description for the process. It's not the greatest website but should be helpful.  JBM doesn't carry the TK26 stuff.  I've also seen a how-to for some KZ440 diaphragm rubbers on EB. I don't know how similar the TK diaphragms are regarding installation.  JBM >>> jbmindustries.com/

wrote:

wrote:

I recently fixed a small tear in a diaphragm using PPG PS890.  This is a polysulfide material, designed as a fuel tank sealer for aircraft.  It's a two-part catalyzed material that sticks well to the existing material.  If the cracks you mention are up near the edge of the top, and don't extend down very far into the working area of the diaphragm, that stuff may work.  

It's quite expensive, and has a short shelf life (6 months, or something like that).  We throw a lot of it away due to expired shelf life.  After expiring, it's still good for a month or two, before it gets hard inside the tubes.  There is a chance that I can get my hands on a tube of recently expired material for you to try.  That will save money.  Message me if you want to look around for some...

When I try to PM I just get an error message.  Also signed up for email notices for subject posts but I have never seen one.

Some searching on this site and others seemed to suggest Plastidip or Honda/Yamabond being good options.  I suppose there is no consensus? 
Thank you for the help!!

You need a material that isn't affected by gasoline.  Threebond makes all the Kawabond, Yamabond, Hondabond, and Suzukibond materials, and they vary in chemistry depending on application.  For example, the stuff most commonly used to seal crankcase halves is an acrylic sealant, but there are also "bond" materials which are RTV.  I think you will need the RTV stuff, as long as it holds up to gasoline.  Many if not most RTV's won't.  Anyway, the PS890 (polysulfide)  is a vastly superior material to that stuff.  I'll look around where I work on Tuesday to see if we have any recently expired stuff waiting for the scrap bin.  Alternate to that, you can buy a tube.  Warning, though, it's not cheap.

Edit: this may be your best bet.  $25/small tube.  It's not PPG PS890, but similar.  You have to mix it all at once, so you will have to prep all the diaphragms by careful cleaning and drying before starting.  This stuff is goopy, and don't come off fingers easily.  It also dries SLOW.  It's the best stuff available, that I know of, for fixing small tears in diaphragms, though.

www.aircraftspruce.com/catalog/appages/prosealant.php

wrote:

I did find this site but not sure how they mount/install nor if they are well known and would actually send them to me, never tried to get anything outside of the USA.
nrp-carbs.co.uk/shop/index.php?route=com...search&brand=GPZ550H
It would be nice to know I had a backup in case trying to repair them did not work out.

If they won't ship to the USA you could have them sent to me and I will forward for the shipping (let me know when PM is working again)

Applied 4 light coats of PlastiiDip that seemed to work well, have dried for at least a week.  Testing them installed and the diaphragm pistons seem to move properly by hand.
Carbs totally gone through again as everything was poked through, sprayed with brake cleaner then blown out with compressed air.  I have owned this Gpz550 since 1997 and was running perfectly when parked as it sat in my garage for about 25 years.  Tank cleaned, new fuel/vacuum lines and a fuel filter installed. (Runs the same without the fuel filter)

At this point it will start fine on choke, idle but will take no throttle over 4-5k rpms.  Just bogs until I back off the gas and it will idle again.
Does anyone know what this bike wants?