SR500 - Carburettor

Our extensive range of spare parts, repair kits, services and accessories leaves nothing to be desired.

The SR500 had three different OEM carburettors during its years of construction.

In the 2J4, the SR500 of the 1978-1983 model years, the MIKUNI VM34SS-2J4 installed.
From 1984 - ca.1990, the 48T of the MIKUNI VM34SS-48T installed. A characteristic feature of these carburettors is the choke lever, which is pressed down to operate it.
The 48T built between 1991 and 1999 was equipped with the MIKUNI BST-34 delivered. This has a round choke button that is pulled to activate it.

The KEDO carburettor program includes almost everything to keep the increasingly rare OEM carburettors alive.

For all those who want to get a little more power out of their SR500, we also have something in our program:

SR500 "Tuning carburettor"

  • MIKUNI TM36/TM40 (flat slide carburettor)
  • MIKUNI VM36 (round slide carburettor)

OEM-CARBURETTOR

MIKUNI VM34SS
MIKUNI BST34

TUNING CARBURETTOR

MIKUNI TM36 / TM40
MIKUNI VM36

MIKUNI VM34SS

The "early" SR500 models, the 2J4 of the 1978-1983 model years, were equipped with the
MIKUNI VM34SS-2J4 .
The SR500 48T was produced from 1984-1989 with the only slightly modified carburettor VM34SS-48T provided.

The VM34SS is a fully equipped round slide carburettor with a 34 mm passage. A little more complex to maintain but with many advantages. 

The VM34SS was slightly modified several times during its construction period.
On the 2J4, the pin of the accelerator pump diaphragm was changed from 1979 to 1980. In 1984, during the transition to the 48T, the shape of the idle mixture control screw was changed from a conical to a stepped tip shape.

Differentiation between the VM34SS variants

From the outside, the VM34SS carburettors of the 2J4 and the 48T can be distinguished by a small "stamp" on the left-hand side of the carburettor in the direction of travel (see illustration).

With the 2J4 carburettors, there is either 2J4 or 2J2 to see.

The 48T carburettors have there 48T or 48U imprinted.

These variations must be taken into account when selecting spare parts.

In addition to seals and nozzles, there are three different diaphragms that are considered wear parts.
Today's gasoline can cause them to dry out and crack after just 6-8 months of use.

The membranes of the VM34SS

  • The accelerator pump is located at the bottom of the carburettor, offset to the side, and injects a small amount of additional fuel into the intake tract when the throttle is pulled up quickly in order to enrich the mixture for the moment. This prevents choking during acceleration. It is activated via the side push rod and the lever at the bottom.
  • The safety valve at the bottom center prevents the accelerator pump from injecting fuel when the engine is not running. A diaphragm is also installed here.
  • The air-cut valve is located on the side of the carburettor.
    A third diaphragm closes an air duct when the throttle is released and enriches the mixture. This reduces and prevents the exhaust popping in overrun mode ..

Common symptoms of leaking diaphragms are

  • The safety valve is leaking and enriches the mixture: Engine starts even without choke, or stalls after kicking about 3-4 times when the choke is activated.
  • The air cut valve is defective: The mixture is over-rich and the engine stutters from approx. 80-100 km/h, as fuel is sucked in through the defective diaphragm.
  • The accelerator pump flange is leaking: The engine stutters when the throttle is drawn up. In addition, petrol droplets may form on the underside of the carburettor.

Modifications to the VM34SS

The accelerator pump diaphragm was modified from 1980 onwards.

Please check the pin length here!

Item no.: 27986
Accelerator pump diaphragm of the 2J4 until 1979
Pin length 13.4 mm

Item no.: 28696
Accelerator pump diaphragm of the 2J4 from 1980
Pin length 12.0 mm

Although the OEM accelerator pump diaphragms used have different pin lengths, the "newer" diaphragm - the one with the shorter pin (Item no.: 28696) - can be used in all VM34SS carburettors without any problems.

In carburettors for the US market, the diaphragms of the safety valve were attached at four points.

Item no.: 28195
Diaphragm safety valve (4-point attachment)
US models ONLY: SR500'80-'81 US, XT500G'80 US, XT500H'81 US

During the transition to the 48T in 1984, the shape of the Idle mixture adjusting screw was changed.

Item no.: 28190
Idle mixture adjusting screw incl. spring + O-ring for 2J4 up to 1983
conical tip shape

Item no.: 28584
Idle mixture adjusting screw incl. spring + O-ring for 48T, 1984-1989
stepped tip shape

Carburettor rebuild by KEDO

  • Thorough cleaning and inspection of all components. Seals, O-rings, sealing washers and screws are replaced; we only use high-quality, new replacement and original parts
  • Replaced will be main and idle jet, jet needle, needle jet, float needle valve, all diaphragms and idle mixture control screw
  • A KEDO rebuild carburettor is almost as good as new.

KEDO carburettor rebuild service

SR500 2J4 1978-1983

KEDO carburettor rebuild service

SR500 48T 1984-1989

Homemade carburettor rebuild

Of course, we also offer everything you need to overhaul the carburettor yourself.
The following is a small selection of the most commonly required products for carburettor rebuilds:

KEDO carburettor rebuild kit

SR500 2J4 1978-1983

incl. choke piston, springs & ball, sealing ring for the actuating shaft
(Nozzle sizes: HD #300/LL #25)

Keyster carburettor rebuild kit

SR500 2J4 1978-1983

Nozzle HD #300/LD #25, incl. choke piston

KEDO carburettor rebuild kit

SR500 48T 1984-1989

incl. choke piston, springs & ball, sealing ring for the actuating shaft
(Nozzle sizes: HD #300/LL #25)

Keyster carburettor rebuild kit

SR500 48T 1984-1989

Nozzle HD #300/LD #25, incl. choke piston

To the complete VM34SS program:

MIKUNI BST34

The "later" SR500 "48T" models, model years 1990-1999, were supplied with the MIKUNI BST-34 carburettor.

Carburettor with throttle valve. Less complex than its predecessor with correspondingly fewer spare parts required.

In the SR500 the successor to the VM34SS and the last carburettor before the design of the injection in the SR400FI

The carburettor is controlled via a throttle valve. A diaphragm controls the flat slide movement. The MIKUNI BST34 came from the Yamaha component shelf and was used in other models of the brand in the early 1990s. An appropriate successor to the VM34 - also with regard to the further development of the SR500.

In addition to the rebuild kit 94043 and the gas slide/diaphragm combination 10249 we offer the Air-Cut valve cover 29122-1 on. As the original plastic part ages relatively quickly and becomes brittle, a good replacement is important here.

Mikuni BST34 - Carburettor rebuild

Here is a small selection of the most frequently required products for the carburettor rebuild:

KEDO carburettor rebuild service

SR500 48T 1990-1999

For all those who want to have their carburettor professionally overhauled, we offer this as a service by our master mechanic.

  • Thorough cleaning and inspection of all components. Seals, O-rings, sealing washers and screws are replaced; we only use high-quality, new replacement and original parts
  • Replaced will be main and idle jet, jet needle, needle jet, float needle valve, diaphragm and idle control screw if necessary (also repaired in some cases)
  • A KEDO rebuild carburettor is almost as good as new.

KEDO carburettor rebuild kit

SR500 48T 1990-1999

Mikuni BST-34 carburettor (jet sizes: #165/#45)

Gas slide incl. diaphragm

SR500 48T 1990-1999

For original BST34 carburettor
OEM-Vergleichs-Nr. 2LN-14940-00

Air-Cut valve cover

SR500 48T 1990-1999

For Mikuni BST34 carburettor incl. small O-ring at the top and large O-ring at the bottom

Carburettor screw set

SR500 48T 1990-1999

For original BST34 carburettor

To the complete BST34 program:

MIKUNI TM36 / TM40

Tuning flat slide carburettor

We also offer the current flat slide carburettor from MIKUNI as an alternative carburettor for SR/XT/TT models in two sizes with 36 and 40mm passage.

This carburettor is definitely a tuning carburettor and shines with its spontaneous throttle response.

While the TM36 can be ridden with unmodified original components (intake, engine, exhaust) of the SR500, the TM40 carburettor is only suitable for top performance with heavily modified engines.

A precisely guided flat slide is controlled via a cleanly mounted mimic. Equipped with a choke and accelerator pump, both models are controlled in the same way as the original carburettor with an opener and closer cable. As with the VM36, the advantages come into their own in combination with sporty exhaust systems and racing air filters.

MIKUNI TM flat slide carburettor

  • Easy way to more power without changes to the engine; power increase depends on intake and exhaust, an increase of 3 hp and more over the entire speed range is possible
  • Equipment: Carburettor with accelerator pump, throttle slide with forced actuation (opening and closing), cold start device (choke) and vacuum connection (if necessary to control a vacuum fuel tap).
  • Fits the SR500 without modifications to the air filter box.
  • Not street legal.
  • We offer various tuning kits for easier carburettor tuning.

TM36 flat slide carburettor

SR500, TT500, XT500

WITHOUT kit, Not street legal
Fuel/vacuum hose connections 8/6mm

TM40 flat slide carburettor

SR500, TT500, XT500

WITHOUT kit, Not street legal
Fuel/vacuum hose connections 8/6mm

TM36 flat slide carburettor

Here is a small selection of the most frequently required products for the TM36:

For Adjustment:

KEDO TM36 fine tuning & mounting kit

SR500-'89

KEDO TM36 fine tuning & mounting kit

SR500'90-

incl. connecting rubber to the air filter box

Universal nozzle set

Mikuni TM36

4x idle jet #12.5-#22.5, 5x main jet #127.5-#140, choke jet #25

To overhaul:

TM36 carburettor rebuild kit

Mikuni TM36/TM40

Contains all gaskets, jet needle, needle jet, mixture control screw, float needle valve, bellows, but without jets

Intake manifold for TM36

Mikuni TM36 & SR500, TT500, XT500

For TM36 flat slide carburettor and cylinder head without intake port machining, incl. clamp

Intake manifold for TM36/TM40

Mikuni TM36/TM40

For TM36/40 flat slide carburettor and cylinder head with intake port machining, incl. clamp

To the complete TM36 program:

TM40 flat slide carburettor

Here is a small selection of frequently required products for the TM40:

KEDO TM40 fine tuning & mounting kit

SR500-'89

KEDO TM40 fine tuning & mounting kit

SR500'90-

Intake funnel set

for Mikuni TM36/TM40

To the complete TM40 program:

MIKUNI VM36-4

Tuning round slide carburettor

This carburettor also comes from MIKUNI Japan.
Our technically uncomplicated and inexpensive alternative to the original carburettor of the the 500cc models

With a 36 mm passage, it certainly has a performance-enhancing effect.

The VM36 carburettor is only operated with an opener throttle cable centrally above the round slide. The diameter on the air filter side is an impressive 63 mm.

We have therefore developed an adapter ring for the 48T air filter box that enables problem-free installation.

Type B main nozzles are used for tuning.
For an SR500 with air filter box and performance manifold, you are in the range of a 220-240 main jet and a 25-32.5 idle jet.

MIKUNI VM36-4 round slide carburettor

  • For SR500 with original fuel petcock, an intake manifold with vacuum connection Item no. 29440 or a fuel petcock without vacuum control is required.
  • Actuation via ONE throttle cable.
  • Not street legal.
  • For 2J4 models, we recommend converting to a 48T air filter box

Throttle cable see Item no.: 32202 / 32203 / 41184

Here is a small selection of the most frequently required products for the VM36-4:

KEDO VM36 carburettor rebuild kit

Contains gaskets, nozzle needle, mixture control screw, float needle valve, clip, but without jets

Intake manifold with vacuum connection

SR500 (with Mikuni VM36 carburettor and vacuum-operated fuel tap)

Adapter set VM36 carburettor to original 48T air filter box

SR500'84-'89, SR500'90-

The connecting rubber between the carburettor and the air filter box must be shortened; please order this rubber (item no.:. 28180) at the same time if necessary.

To the complete VM36-4 program:

Carburettor tools

Whether special wrench, jet change tool, MIKUNI PocketTuner, tool tank or starting aid spray - here we have compiled special tools for working on the carburettor.

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