Where to find vacuum diaphram

I have a 1983 kz 550 f1 shaft. The throttle vacuum valve diaphrams are stiff and need replacements. Any ideas on where to get just the rubber part?

I'm new to this forum btw. TIA.

Evidently, they are still available from Kawasaki.

www.partzilla.com/product/kawasaki/16126...2cee54355cc549e7ebae

WOWSERS! Those are expensive little devils aren't they...…$191.00 retail.

Rick H.

Yes, they are. For most of these old bikes, the diaphragms are either shockingly expensive or not available at all.

No eBay APP ID and/or Cert ID defined in Kunena configuration

Rick H. wrote: WOWSERS! Those are expensive little devils aren't they...…$191.00 retail.

Rick H.

Same part number on Ebay:

I have saved money by taking the part number and an afternoon and calling Kawi dealerships and asking them to check their stock.. you get them much cheaper even with shipping.. a little time and a few phone calls voil'a

No eBay APP ID and/or Cert ID defined in Kunena configuration

daveo wrote:

Rick H. wrote: WOWSERS! Those are expensive little devils aren't they...…$191.00 retail.

Rick H.

Same part number on Ebay:

Still $90.00 USC plus shipping but much better than $191.00. Unfortunately, when you NEED something you are at the sellers mercy. I know from things I have purchased.
Rick H.

The problem is that they integrated a flimsy, cheap rubber part with an expensive, machined metal part with no easy way to remove the rubber part. You have to break the plastic attachment rings to get the diaphragm off.

I went down a rabbit hole of research for a similar problem on Kz400's. Some companies are making a replacement rubber part, but making it different so it can be retrofitted to an old slide where the attachment rings were broken off. This involves molding in a heavy band where the diaphragm holds the slide. These guys might save these bikes. But so far, I don't know if they've come up with a replacement for the KZ550's TK26 carbs or ZX550's TK27 carbs.

Have you tried JBM industries? They make just the CV diaphragms to put on your slides. Carb holders too.

I tried a few different diaphrams for old Harleys and several other mikunis. None of them are a good fit. What about a retrofit with an older set of kz550 carbs? Its easy enough yo change the manifold boots and jets. I did some shopping around and found used sets as low as $100. That plus rebuild kits and boots would be around a $200 fix. Keep in mind, this is a total revamp bike I picked up, so I have plenty of time to work on it.

The newer engines had the carb-holder mounting bolts farther apart so the older carb-holders don't just bolt-up. they have to be modified. The holes have to be made into slots. Also the sealing surface is reduced so you have to really watch for vacuum leaks.

I was aware of the modifications to the carb holders. Of course I'll have to do some jetting on the older ones because the shaft driven had lager jets to accomadate the extra load. But it seems that a small modification and around $200 is the way to go. Anywhere from 650 to 800 bucks to get a flimsy rubber diaphram is just not a smart option in my opinion. This bike is already undergoing a lot of modernization. (All led lighting, digital Speedo, new handlebars, exhaust reconfiguration, ECT.). If I were looking to restore it, I'd spend the money, but I just want to ride this bike with a few comfort and asthetic upgrades. Thanks for all of the info guys! I look forward to sharing the journey on this bike with all of you.