Suzuki DR650 Carburetor Page
The stock Mikuni BST40SS carburetor in DR650s leave much to be desired. This is especially true with the pre1996 DR650s that like to stall at low RPMs.
Stock Pre 96 Carb
As the DR650's carburetor is barely adequate and a carburetor upgrade can make a huge difference in perceived performance, responsiveness, fuel effeciency and reliability.
At least for the newer DR650 the jet configuration on the Mikuni BST 40SS carb is as follows:
main 140, pilot 42.5, needle 6F19 clip on 3rd slot (Australian, Canadian and UK needle)
US models use a 6F23 fixed clip position jet needle and a Y-5M needle jet
The Mikuni TM40 Pumper Carburetor used for Harley Davidson bikes is more or less a bolt on upgrade. You can tweak the stock throttle cables to work and the carburetor mates up with both pre and post 1996 DR650s - although it is pretty tight on the pre 1996 DR650s. This drastically improves responsiveness and makes kick starts much much easier. It will take a sluggish bike and allow it to lift the front wheel without feathering the clutch.
Thumpertalk - Mikuni TM40 Pumper Carburetor kit from procycle.com - anygood?
The Keihin FCR-MX has also been used on newer DR650s with what sounds like pretty impressive results.
Thumpertalk - Keihin 39mm FCR-MX Install
mxrob.com mxrob_007 - DR650 mod
ADV Rider pre'96 thead - FCR on 95 DR650SE - note intrusive starter
These have been used in DR650s and other Dual Sports.
The choke cable is prone to moisture accumulation which can cause cable corrosion and accumulation of water in the choke. This can lead to unexpected engine cutoff when the handlebars are turned.
To avoid choke cable problems, the entire cable can be removed and a aftermarket Hand Choke can be installed directly in the carburetor. You will need to notch the throttle wheel stop with a file to allow for full throttle without hitting the new Hand Choke Conversion.
After installation of the choke knob, choke adjustments will need to be made directly on the carburetor when starting and warming up your bike. This isn't too difficult to do while sitting on the bike.
If you modify your air intake box (see the Air Filter page), the you will need to adjust the carburetor and most likely need to rejet the carb to avoid running too lean. Figuring out the best setup can be quite the challenge, but luckily there are a few kits and pointers available to those that wish to tweak.
List of tweaks:
Dynojet Research's kit 1990-2009 DR650 Satge1&2 kit Part# 3138
Factory Pro - 1996-2006 kits plus carb parts (jets)
Sudco part catalog
This is not a mod I am familiar with. You may find some information and a start at MicroSquirt.com
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