Cracked worn or torn diaphragms can allow imbalance to carburetors causing one cylinder to work harder than the other. This diaphragm set does NOT include new throttle slides. This is a easily installed rubber part that goes on your old slide. The rubber is attached to the slide by pushing the thick section over the swagged lip that held the plastic washers. The thick section of rubber grips the slide and replaces the plastic washers. The pictures should explain how this works. Please print these instructions. We guarantee that those that buy them will like them, or your money back. Q.Your diaphragms work great. Do you have the carb holders ready? 1979 Yamaha XS650. Regards, Waldo A. Yes we do have the carburetor holders, including those straight ones for early '70 thru '73. See our other page or watch on Ebay. I just received the new BS38 diaphragms, and am extremely happy. Very nice work, and I can't thank you enough for saving the carbs on my 79 XS. Thanks a million! Norm McRae Great alternative to $300 NOS slides. Works as advertised. Buyer: wch69sooner2010 ( 3 ) Apr-09-10 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#230435468325) As Usual...PERFECT!!!! Buyer: spydercycleworks ( 3184) Mar-31-10 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#330413174303) Super quick, great product and seller! Thanks Don Buyer: bluebikerblan ( 57) Mar-24-10 Yamaha XS 650 Carburetor Holder Socket Boots USA made (#330411790711) Item worked great and quick delivery very pleased Buyer: gerald.423 ( 4 ) Sep-14-09 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#330355707704) Thank you. Very cheap shipping A+ Good part at a super price wish I had got more Buyer: jeremyb977 ( 26) Jul-09-09 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#230348064346) Worked like a charm. I wasn't sure if I'd ever be able to find this part again. Buyer: shadowstep07 ( 20) Jun-22-09 Great product Buyer: sherrieakin ( 36) Jun-20-09 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#230348064346) Nice parts-good service Buyer: senpga ( 69) Jun-08-09 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#330333032461) Quick and accurate Buyer: joara172 ( 29) Jun-08-09 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#330333032461) Awesome great part Buyer: 970_anchondo ( 18) Sep-03-09 YAMAHA XS, TX 650 Mikuni BS38 CV Carburetor Diaphragms (#230359062132) * Constant velocity carburetors actuate the throttle slide and needle at anything over a fast idle. The atmospheric depression or vacuum caused by the venturi of the cut-away is used to raise the slide by means of the vacuum on the top of the diaphragm. ( There is a communication hole to the venturi in the throttle slide.) Made in USA on limited basis with high quality rubber. Reasonable shipping worldwide! Email us and let us send you a Pay Pal Invoice: jbmindustries@att.net |
Yamaha SX, TX 650 & Kawasaki KZ-750 Carburetor Diaphragms for
Mikuni BS38, BS36, and BS34 CV constant velocity carburetors. This easy
to install part can cure engine stuttering, unwanted acceleration, uneven
and unbalanced carburetors caused by leaking or worn diaphragms. Until
now replacement meant you had to buy an expensive new throttle slide.
Please state which carburetors you have when ordering.
Mikuni BS38, BS36, and BS34 CV constant velocity carburetors. This easy
to install part can cure engine stuttering, unwanted acceleration, uneven
and unbalanced carburetors caused by leaking or worn diaphragms. Until
now replacement meant you had to buy an expensive new throttle slide.
Please state which carburetors you have when ordering.
This pair of Yamaha TX or SX 650 carburetor
diaphragms fits Mikuni BS38 CV constant velocity
carbs. Easy and inexpensive fix & made from aircraft
quality rubber so they will last. JBM "TSR" Compound
diaphragms fits Mikuni BS38 CV constant velocity
carbs. Easy and inexpensive fix & made from aircraft
quality rubber so they will last. JBM "TSR" Compound
The first step to install the new diaphragms is to cut the
plastic retaining washers from the original slides as shown.
( Remove stuck slides by placing carburetor body under a
100 watt lamp to warm it and soften varnish. )
plastic retaining washers from the original slides as shown.
( Remove stuck slides by placing carburetor body under a
100 watt lamp to warm it and soften varnish. )
Install the new diaphragm by pushing it over the lip on
the old throttle slide as shown. Hard rubber tire fits tightly
to slide. We are asked about adhesive on this part, and
while "Super Glue" will work, you really don't need it.
the old throttle slide as shown. Hard rubber tire fits tightly
to slide. We are asked about adhesive on this part, and
while "Super Glue" will work, you really don't need it.
Use fine sandpaper or Scotch-bright pad to clean
the groove and remove any sharp corners that
might cut the diaphragm.
the groove and remove any sharp corners that
might cut the diaphragm.
Install your needle and clip as shown here.
Position the throttle slide and diaphragm as shown with
the cut-away facing the open mouth of the carburetor.
Roll the diaphragm a bit to push it into the groove.
the cut-away facing the open mouth of the carburetor.
Roll the diaphragm a bit to push it into the groove.
Place a dot of paint at the "key" tab location for easy
future removal and positioning.
future removal and positioning.
Place the slide return spring and check that the
diaphragm rolls properly.
diaphragm rolls properly.
- Install the top cover and check for smooth
operation. - A smoothly moving slide is needed as only a
very light return spring returns the slide. - A small hole in the throttle slide is what allows
the venturi vacuum to operate the slide. This
constant velocity carburetor prevents stalling
and gives smoother running than other direct
acting carburetors. - Some folks want to use an adhesive on the
slide, and this will not harm anything, but be
sure not to get adhesive on the sides of the
slide.
with carburetor cleaner, remove the diaphragm and all
rubber parts first. ( Diaphragms are sometimes called
membranes. )
- BS38 carbs use 77mm diaphragms
- BS34 carbs use 73mm diaphragms
Only $39 a pair
To order:
Call 330-678-9537
email: jbmindustries@att.net
Visa/ MasterCard..
To order:
Call 330-678-9537
email: jbmindustries@att.net
Visa/ MasterCard..
| CALL: JBM Industries 330-678-9537 |
 | |  | |  |
| To order: Send check or MO to: JBM Industries 3761 Morley Drive Kent, Ohio 44240 USA Request a Pay Pal Invoice: jbmindustries@att.net Or phone: 330-678-9537 |
| Domestic & Foreign Shipping only $5.80 per order for any number of pairs by Priority Mail |
| Be sure to visit our page for Carburetor holder socket boots. |
ORDER: MIKUNI BS38-CV Diaphragms if
you have a Yamaha 650 twin made from
1970 thru end of 1979. ( Sold in pairs )
ORDER MIKUNI BS34-CV Diaphragms if
you have a Yamaha 650 twin made in 1980
until end of production.
you have a Yamaha 650 twin made from
1970 thru end of 1979. ( Sold in pairs )
ORDER MIKUNI BS34-CV Diaphragms if
you have a Yamaha 650 twin made in 1980
until end of production.
Step#1
Step #2
Step #3
Step #4
Step #5
| A finished Mikuni BS38 CV carburetor |
Step #6
Step #7
Last updated 06/22/10
| This is a photo of the pair of diaphragms or bellows that you will get to restore your carburetor. |
BS38CV fits these models:
Yamaha XS-650 1970-thru 79
XS 650 A,B,C,D,E,F,SE,SF
TX-650
XS-1, XS-2
KAWASAKI KZ-750 Twins
Yamaha XS-650 1970-thru 79
XS 650 A,B,C,D,E,F,SE,SF
TX-650
XS-1, XS-2
KAWASAKI KZ-750 Twins
| Special note when installing BS34CV Diaphragms and slides: While your BS34 slide may not have a cut-away as shown on the BS38 above, it is important that the vacuum hole is positioned towards the engine. |
| The "Hard Rubber Tire" is what holds the diaphragm to the slide. |
| If you plan to install these diaphragms on something other than a Yamaha, please check the outer groove diameter before you order as not all BS34CV carburetors use the same diaphragm !! DOES NOT FIT BS34SSCV |
| BS38CV 77 mm OD of Diaphragm BS36CV 73 mm OD of Diaphragm BS34CV 73 mm OD of Diaphragm |
| SIZES we have at this time: |
Note: BS36 carbs were used on certain
FJ1200, 86-93
XJR 1200-1300
XJ900 F
Please measure OD of Diaphragm to
be sure.
FJ1200, 86-93
XJR 1200-1300
XJ900 F
Please measure OD of Diaphragm to
be sure.
| To see if you need new diaphragms, just hold your old diaphragms up to a strong light. If you see any light passing through, you need replacements. |