JBM Industries

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Keihin Plastic Slide Replacement Diaphragm Page

Installation of JBM Industries replacement diaphragms on Keihin CV carburetors used on vintage motorcycles such as the Honda V4 engined bikes like VFR400R, VFR400RR, V-65 Magna, and also NC-30 , VTR250, PC800. These vintage Honda motorcycles have a problem with old diaphragms that shrink from ethanol fuel and age. Some are destroyed by carburetor cleaners sprayed down the wrong hole while the diaphragm or membrane is still on the carburetor.
Installation of these replacement diaphragms is not difficult, but should only be done by someone with mechanical skills. This diaphragm was replaced in 15 minutes including the time it took to make these photos. This diaphragm is used on other makes of vintage motorcycle, including the Honda 1100 V4 engine, CB1300, X4, etc. Please see our "HOW TO MEASURE" page. The Keihin VG series page may also be helpful to you, so please check it out.
This page shows installation of JBM part K-72-S , a 72 mm diameter diaphragm or librane with key. This shows mounting the central tire on a plastic CV carb slide or piston. JBM Industries uses TSR compound.

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Use small, sharp, side cutters, or jewlers saw.  Slides are brittle.

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Roll the diaphragm when you install it so it looks like the photo above.

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Note:  All JBM diaphragms are made from our special TSR compound for the longest lasting parts available.

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Honda 360 & 350: Air holes in the slide go on the intake side!

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Order K-78mm Keihin Diaphragm for Honda 360

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Order K-73mm Keihin for Honda CB or CL 350

Diaphragms shown here fit the Keihin CVK 36 used on the Kawasaki Vulcan 1500cc & Ninja 900 "FLAT SLIDE CARB"
See note Below about Vulcan VN750 VN700

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NOTE ON K-67 Diaphragms: These definitely fit and work on my bike, so they'll work on any Kawasaki Vulcan 750 (VN750) and 95% certain that they'llwork on the VN700 because that was just the 750 in a 700cc version due to the Harley tax in the 80s. These bikes have two Keihin CVK34 carbs in a v-twin setup.

What our Customers are Saying...
"1983 Honda Shadow VT750
I used a set of these diaphragms and they are Great. When installed they are slightly thicker which made it just a touch stiff. After I got the bike cranked, it ran great. Thanks for producing something that Honda quit producing.
Thanks again,
Mike"
"I received your products earlier today for Honda V-65 Magna, and I can't believe how fast they got here! The diaphragms are amazing. I have decided to replace the other two so please ship two (2) more K-72-S diaphragms to me. I will look for your invoice in Pay Pal. I plan to pass your info along to some of the other retro bike dealers and garages in the area. Hope you can benefit. Thanks for everything. ....Brian Tucker"
"Hey Don.
I just wanted to say thank you. Those K-72-S diaphragms you sold me fit my 2001 Honda shadow spirit like a glove. Appreciate you getting them mailed out as quickly as you did. I will definitely tell all my friends about your products.
Karol Pettay"
"VFR400R
Hi (JBM)

I just wanted to give you a brief update. I was finally able to install and test your slide diaphragms. The installation went well. I used a 5-minute epoxy rather than Super Glue. That seems to hold very well (maybe too well if I ever needed to replace these). The only bothersome part was some of the slide tops broke off more than I would like when removing the top ring. It looks ugly, but works fine.

We have only run the diaphragms for a few dyno pulls compared to our other carbs, but your slides seem to react better, snappier, and during a slide-speed test, yours respond BETTER than ours :-) The bike makes the same, or better horsepower and doesn't seem to have any hesitation or slowing in pull. These were all my concerns, that are now gone.

I was also able to ride the bike for one session at the track. It felt fantastic! But, it's a much faster bike than I am used to, so I also didn't ride it hard. However, that was an even better test for the diaphragms since I was always at partial throttle in the turns. Throttle modulation was never off or odd.

I will probably be ordering a bunch more here in the next few weeks. Are you limited in supply? I see the need for 12 diaphragms right off the top of my head.   There maybe another 12 to 16 diaphragms needed after a quick e-mail to the group. If you need to make them, what is your turn-around time?

Thank you again for your help with this. We are very excited to have found a solution to a problem that has plagued us for a very long time.

Regards,
Mike Norman
G-Force Engine Development
www.mngforce.com        There is no such thing as "Too Fast""
"Hi mate my name is Lawrence borg I recently brought some diaphragms of u and they are brilliant. Better then the original by far. I would also like an invoice for another 6 Keihin K'72,S diaphragms for My Honda VF 1000 F2 Its a 1985 model please. Laurie. Australia thanks mate."