Carburetor diaphragm repair that works

[lovethosetwins]

Ok, so I've signed up for this forum to spread the results of my experimentation. Please, Mr. Moderator, put this into the appropriate place, this is the closest match to the right forum I can find...

Ok so your old bike's carb diaphragm has a little pinhole in it, or you've got a little tear like mine does from being old and maybe a backfire or something. So you go to the stealership or check online and you can't find a replacement anywhere. You may stumble upon services that will re-diaphragm any old carb slide, but the wait time is a month and you can't afford the 170 bucks a piece. Never fear, I have found a solution.

Carb diaphragms are made of nitrile rubber and so are nitrile gloves (big surprise right) so I experimented on several gloves with various adhesives that I thought might work and eventually I found one.

First up was liquid electrical tape. The liquid electrical tape bonded the glove together really quick and held pretty damn strong. Much stronger than needed for a diaphragm. I then tested its resistance to Gum-out (which you should NEVER use on CV diaphragm carbs btw!) and the gumout dissolved it quick. Gumout also slackened and ate through the gloves after several minutes. Well scratch that one, I wanted something that would stand up to gasoline and the occaisional capful of cleaner.

Next up, weatherstripping adhesive. This was a good candidate because it seems to hold soft rubber very well for nearly forever. Same problem as the liquid electrical tape. They both smell similar as well which might indicate the solvent being usedm which is easily cut with gumout. I would imagine that xylene and laquer thinners would have the same effect. I know after painting with nitrile gloves (urethanes, laquers, clear coats) that the gloves are resistant but will eventually break down anyway. This reinforces the NEVER USE CARB CLEANER SPRAY IN A CV CARB advice.

On the third try, and after reading some industrial adhesives literature, I came accross a family of adhesives that include regular super glue, and 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). And speaking of HNBR (the green rubber), I wish people would push keihin and mikuni and the like to use that stuff in carbs. When you look at what they resist and the temps and pressures they resist, they are CLEARLY the choice for using in a casty gasoline / solvent environment especially where there is heat involved.... But I digress. So gorilla glue is your best bet. Superglue cures too stiff, and will degrade over time with humidity (crazy huh?). 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.

Alternately, some people say that the spray tool dip available from napa auto parts works like a charm. The only problem here is you are increasing the thickness of the diaphragm and that will decrease the response rate of the slide. It's not that big of a deal to get by but still... The main concern is keeping the hole closed #1, and keeping it airtight #2. You could always use a small bead of gorilla glue to hold a tear closed and spray rubber over it for added protection. You could even gorilla glue some nitrile rubber glove over a larger tear. But as I said, response rate will be affected. If you think about it though, there are big springs which hold the slide down, and the suction is really what makes them rise, so as long as they still slide up and down relatively well, and are sealed you should be fine.

The bottom line is, this fix will cost you under 10 bucks and get you going in 24 hours. While you ride on it, look for a new diaphragm, or better yet, save up some money for a set of VMs or something that doesn't use those damn diaphragms!

Now if I can only find a place to get an o-ring for my needle jet...

Rob
80 KZ750 G1 LTD 2
99 Honda Shadow VLX
69 Honda CB175
87 nq50 spree
89 elite 50e

[acergremlin]

Or you could try here, you should get a full set for the price of an original

NRP motorcycke carburettor repair specialist

[lovethosetwins]

Originally Posted by acergremlin

Or you could try here, you should get a full set for the price of an original

NRP motorcycke carburettor repair specialist

They do have them, but at around 70 bucks a piece, and my current low cash situation, I've gone the route of the gorilla for now That is a good resource though. Another great site (through pretty spendy) is Honda Motorcycle Parts, Kawasaki, Suzuki and Yamaha Motorcycle Parts - ATV, Classic Bike, Dirt Bike Parts they have lots of out of production new parts..

[herk]

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[wirkus24]

I tried out your recommendation and found it to be a true solution. Looking at $103 to replace the part, I figured I would give it a shot. The tear in the diaphragm was about 1", so I didn't figure the gorilla glue and glove method would work, but sure enough: after I let it set up, I put it all back together and found it working, and working well. I thought the gorilla glue was a little stiff, but the slide would move up with just as much air coming in as the other carb.
Thanks for you testing and for sharing your knowledge.

[kawpaul]

This is one time dragging up an old thread put some knowledge in my head.

[kennylewis]

Thanks for your post. My son has a 2005 Ninja 250 with a tear in the diaphragm. He only paid $1,500 for the used bike. Paying $122 for a new diaphragm seem more than unreasonable.

Since Gorilla glue expands three to four times the amount used, how did you correct the foam expansion?

I have the nitrile glove, the gorilla glue, and am ready to go!

Kenny

[apbling]

I did this to my 1980 750... I hate to jinx it, but it's been holding for the better part of 8 months. Maybe only 65 actual miles, but lots of running in the garage and such. Beats $75 for a 30 yo junk yard one.

[Polar_Bus]

Originally Posted by kennylewis

My son has a 2005 Ninja 250 with a tear in the diaphragm. He only paid $1,500 for the used bike. Paying $122 for a new diaphragm seem more than unreasonable.

Welcome to the world of expensive OEM Kawasaki parts. No different markup than OEM Ford, GM..... The only difference is you generally can't zip over to your local NAPA or Autozone mexican/Malaysian parts replication company for a spare part.

Lastly you think Kawasaki parts are expensive ? Be glad you don't own a Yamaha...