• JBM Industries has produced a innovative replacement diaphragm for vintage motorcycles using the Hitachi HSC32 constant
    velocity CV carburetors.  We also make diaphragms for Hitachi HSC40 carburetor on Yamaha Virago. (78 mm diameter groove).
  • These diaphragms fit certain Yamaha Maxim and Seca models such as the XJ650G & XJ550. Order 3 for Yamaha XS850G
  • Order 68 mm or 78 mm diaphragms measured on groove OD. (Do NOT try to measure old rubber). HOW TO MEASURE PAGE
  • JBM replacement diaphragms are easy to install by the owner with limited tools required.
  • These are long lasting diaphragms made of TSR compound able to run in fuel containing ethanol. Heat resistant, too!
  • These diaphragms can restore smooth running and original fuel economy to the motorcycle. They give a smooth rolling action to
    drive the throttle slide.   Takes about 15 minutes to install and that includes taking the photos.
  • Less expensive and easier to install than other types of replacement diaphragms for vintage bikes.
  • Designed to prevent twisting of slide to keep hole and cut-aways aligned. H-68 is being used on some Keihin carburetors as well.
This diaphragm does not come with the slide, as no new slide is needed. All you need to do is to position the slide correctly in your
carburetor. A dot of paint on the rubber can make removal / replacement easy,  ( but a man needs to know his limitations. )
  • H-32 Air Valve Diaphragm is available for $19.50 as shown below if you need one. Fits HSC40 carburetor.
Last Updated 09/16/18
These photos should help you identify your Hitachi Carburetor as
there is no name or model numbers on it. This one is a Hitachi
HSC32/4H7.00 from a 1980
Yamaha Maxim XJ650G.
Hitachi carburetors were used on many other vintage motorcycles.
68 mm diameter groove shown here.
Click here to see
Click here to see
Only $19.50 each
To order just email:
Please note the different
lengths on the cover screws.
These diaphragms are
manufactured by JBM
Industries in Uniontown, Ohio,
Click her to see
JBM Industries
Yamaha Virago 78 mm groove
Hitachi 68mm should fit XJ550, XJ650.Yamaha Maxim, Midnight, and Seca from
1981-1984, XJ1100

carburetors were used on different bikes, different years, and different
countries. We offer free exchange, but
you pay postage !!
Order Hitachi 78 mm for Hitachi HSC40
Carburetors used on Yamaha VIRAGO
Diaphragms fits fine to Yamaha XV100 TR1
Check fit of diaphragm in carburetor
BEFORE you remove rings!!!
  • I ride a 1984 Honda VF700 Magna. The H-68 diaphragms (with the addition of an o-ring on the air tab) fit as well as I could have ever imagined. I have no doubt when this
    bike is re-assembled that the carbs are going to work like a dream. Thank you for making such a great product. ..-  Matt Davis,  Shade, Ohio
  • Just send me an invoice as soon as you have more ready because I'll take them, I used them on one bike already and I'm a believer, they worked awsome! ..Thanks, Greg
  • James –product and service was excellent. Diaphragm works perfect and fit was spot on. Please add size to your database for model in subject line. Thanks again for your
    business.  ( Honda VT600 & VLX600 )   Ryan Custer    Note: User found that this Hitachi 68mm will fit Keihin carburetor. ) Info click here
  • Don,   WOW!!!  That's so much better than my old, tired, stiff diaphragms.  Thank you so much. Hitachi  H-68mm   ....Dan Timmons
  • Hello, the replacement Carburetor Diaphragm came it today.The quality of these parts is perfect and better than the original in my opinion.
I am working on Motorcycles since 1979 and was happy to get these high quality spareparts.
Thank you very much for your kindful help and assistance and the fast delivery.    Berlin/Germany WOLF......
  • Thanks for quick delivery. I have mounted the H-78 diaphragm`s on my bike and they work perfect. Thanks very much! Sincerely, Kjell Zanders
  • These H-68 diaphrams fit a 1988 Honda Shadow vt600c - vlx600 perfect with slight modification.  They fit perfect by making a small razor blade cut in the outer ring edge in
    two spots to make room for the screw hole indents but its such a small slice that it would never create a leak.  I'm so thankful for your fast shipping and high quality
    parts.         Chris Habina     NOTE: see photo below.  ( Info about this "HACK" click HERE.)
Click here for
Click for HOW TO ORDER
To prevent rotation or removal:
Some folks want to use Super Glue adhesive on the slide, and
this will not harm anything, but be
sure not to get adhesive on the
sides of the slide. Use sparingly, as solvents are not good for the
To prevent rotation or removal:
Some folks want to use Super Glue adhesive
on the slide, and this will not harm anything, but
sure not to get adhesive on the sides of the
Use sparingly, as solvents are not good for
the rubber.
Click here for HOW TO ORDER
Click here for how to remove and restore a damaged carburetor slide.
Hitachi 68mm diaphragm fitted to a Keihin
carburetor used on Honda VT600.
  • Got the diaphragms in already! And have to say that I appreciate the nice quality for the money. I'll be doing
    another set of carbs and will come back for another batch in the near future.   Thanks again,  Tony Massimino
Don, An update on the (K-72-S) diaphragms:  I installed these diaphragms on 3 Hitachi HSC34 Carburetors. These were
standard issue carburetors on Yamaha XS850 motorcycles from 1980 and 1981. The groove diameter on the Carb itself
is actually 73mm, but the dish and slide groove measurements are the same. Also, the key is slightly smaller on the
Hitachi than it is on the Keihin. With a little trimming of the key, I was able to install them with little issue, and they work
In case anyone asks in the future, These are a great fit for the XS850 with Hitachi Carbs.
From: "Brian Webster" brian.daniel.webster@gmail.com
I have a '82 xj750 Maxim. I have purchased 2 of these H-68 in August the same bike and they work great.  Kevin
Questions about JBM Diaphragm? Click HERE
Questions about TSR material? Click HERE
CLICK HERE to see "ABOUT US" page
I have received the diaphragms today in good order.  6 days!! Must be a record for items sent to Australia. Your package
actually arrived before a similar sized item I ordered from my home State of Queensland!  Thank you again, I will be ordering

diaphragms for my CB360 soon. Kind regards, Adam James
Hi just wanted to leave some feedback on the H-68 slide diaphragms I purchased from you:  they work great on my 1981 Seca
750 rh .. This has to be one of the best products I have ever bought. Saved me a lot of money and I look forward to doing
business with you in the future.   Thank you,  Cory Silver
Thank you so much. The  H-68 diaphragms worked great and fixed my Honda Shadow. The 20 dollars I spent on the diaphragms
sure beat the 140 dollars quoted everywere else. Keep up the good work
Oh, and by the way they worked/went on a 1983 Honda Shadow 500 with a dual keihin carb with metal slides thanks again,   Chris
I purchased two H-78 for my 1982
Yamaha Virago 750 and they work
perfect. Saved me lots of money. You are
awesome. Thanks again . Dennis.
I have previously purchased from you a
set of diaphragms for the Hitachi carbs on
my 1981 Yamaha XJ750 and am delighted
with them.
Kind regards, David Merry