Carb Diaphragm cracked: Fixable?

I needed to change the needles on my BS-38 Mikunis, I went back to the stock ones because it was running a shade rich with the Keyster needles. When I was putting the left piston back in, I held it up to the light and could see a small crack in the rubber out near the edge maybe 1/4" long. The rubber has "ruffles" at the edge and the crack runs in one of those.

I put the bike back together and it still runs pretty good (better with stock needles). Idles smooth, accelerates well, no hesitation. I can't detect any uneven running and it pulls real hard when I rip the throttle open at either low or high speed. The tear may have been there for some time, I can't see anything new except for a slight change from the leaner needles. Spark plugs look OK.

Do I have to fix that stupid diaphram? Can you put some RTV rubber on it or is it toast?

I wondered the same thing, I thought about the RTV on it but I was afraid it would get sucked into the carbs. I just went to a local salvage and bought one. It was 50 bucks for just one. Kinda expensive but I couldn't find any other any cheaper. Then I didn't have to worry about anything.

kzkx wrote:

I wondered the same thing, I thought about the RTV on it but I was afraid it would get sucked into the carbs. I just went to a local salvage and bought one. It was 50 bucks for just one. Kinda expensive but I couldn't find any other any cheaper. Then I didn't have to worry about anything.

problem with a 29 year old bike is I will be getting another 29 year old rubber piece at the salvage.

I found the OEM part at Babbittsonline for $75 each, don't know if it is actually available or not. I'll know soon.....

George of www.wgcarbs.com has mastered some repairs of torn diaphragms...contact him directly for the secret technique...also see the following link for new diaphragms:)

www.nrp-carbs.co.uk/index.htm

i've different procedures over the years and i've never found any that really were acceptable so i won't even try them on customer carb's anymore it's not worth the frustration,i might if the diapraghm cannot be found but otherwise i just buy new.

del

So... I took the thing back out and gave it a really good eyeball and found out it doesn't have a hole..... it has three holes.

And the one on the other side has TWO holes......

Those little suckers are hard to see.

I am going to try the method of sealing it with probond urethane glue as suggested in the PM. I also ordered new ones but have no idea if Kawi still sells them.

Mcdroid wrote:

George of www.wgcarbs.com has mastered some repairs of torn diaphragms...contact him directly for the secret technique...also see the following link for new diaphragms:)

www.nrp-carbs.co.uk/index.htm

Thanks for the link.

Is it correct that I have to send them the slides in the UK and they put the diaphragms on and ship them back?

It looks like the diaphram is only used on the KZ750 twin, so things are not looking promising for getting new ones though Kawasaki

RonKZ650 wrote:

It looks like the diaphram is only used on the KZ750 twin, so things are not looking promising for getting new ones though Kawasaki

The crackhead at the counter of the local Kawi dealer said they showed up as available, but he could be full of crap as usual......

BTW, the one I need is the:

16028-1001

I've used Marine GOOP on carb diaphragms to repair holes.
Cracks are another story. At this stage you've got nothing to lose except for the cost of the tube of GOOP. I would recommend cleaning the diaphragm around the crack thoroughly with some isopropyl alcohol before applying the GOOP. Use as little GOOP as possible to do the job, smearing it along the crack and working it through to the other side and smearing it on the other side as well. Let it cure in a warm place for AT LEAST 24 HOURS before reassembling everything.
Let everyone know which method you're using and how it all turns out.

H2RICK wrote:

I've used Marine GOOP on carb diaphragms to repair holes.
Cracks are another story. At this stage you've got nothing to lose except for the cost of the tube of GOOP. I would recommend cleaning the diaphragm around the crack thoroughly with some isopropyl alcohol before applying the GOOP. Use as little GOOP as possible to do the job, smearing it along the crack and working it through to the other side and smearing it on the other side as well. Let it cure in a warm place for AT LEAST 24 HOURS before reassembling everything.
Let everyone know which method you're using and how it all turns out.

Substitute "probond" for "GOOP" in the paragraph above and that's what I did Friday. I reassembled it today and it seems to be working fine. I have no idea how long, but I suppose I can do it as required. The probond stuff seems well suited for the task. It expands as it cures, so use the minimum to get coverage. You definitely need to clean first, because the first time I didn't and it did not stick well. I pulled off the first glue remnants and then cleaned the edges of the slit with a Q-tip wet with acetone and did the gluing over. The second time seemed to stick well.

I have not been able to buy new slides or find anybody with used ones I could send out for new rubbers.