Considering tuning type stuff such as re-jetting involves experimenting with 3-4 jet changes I find it silly to have to remove the carburetors
every time. Someone on another forum did a step-by-step on how to accomplish this, and I snapped pictures (although he never USED the pictures
)
Jetting a carburetor can be considered step
1 in carburetor tuning! It is critical that you find the right jet size before you move onto fine tuning the needle height. A quick range of jet sizes for the '08+ 250r is as follows:
.................. Keihin/Factory Pro ........... Dynojet
With airbox........98 - 102
......................96 - 100
NO airbox..........108 - 115
...................104 - 110
The process is the same for each carburetor so I'll just go over one:
Step 1: Remove the front fairings. Go ahead! Take those bad boys off. You can leave the fuel tank and seat and everything else put...
Step 2: Hook up a section 2'-3' long to the drain on the fuel bowl:
The hose ID is 3/16" or 1/4". Both will fit over the drain port. Also circled in the picture is the allen screw to open the fuel bowl drain.
There's not much fuel in the bowls so I just used a cap to a can of bondo to pour the fuel into. Don't worry about the fuel petcock or anything. With the vacuum operation on these engines the petcock remains closed as long as there is no vacuum present (ie. the engine is off).
Step 3: Remove the fuel bowl.
I assure you this tool is going to get brought up in a lot of these DIY's, so do yourself a favor and buy one... DO it! (Milwaukee Offset Screwdriver with a ratcheting screwdriver handle)
While the screws from the factory are phillips head screws, Factory Pro includes new allen head screws. So be careful taking the stock screws out as it is possible to strip those suckers.
There are a total of 4 perimeter screws holding each fuel bowl on. Make sure it's one of the 4 screws that hold the fuel bowl on. There is an extra screw down there that is NOT one of them.
Step 4: Remove the jet!
If you did step 3 correctly and drained the fuel bowls, the fuel bowl should drop without any noticeable fuel leakage.
Circled in red on the left is the main jet... Yup no voodoo or searching, it's right there... You have to hold the jet extension tube though while you unscrew the jet so:
Hold the jet extension tube with a boxed wrench and again (with the Milwaukee Offset Screwdriver) throw a flat blade bit on and it should unscrew easily!
... That's it! Put the new jet in and lightly tighten it. I'm not going to list torque specs, but if I DID it'd be in inch/lbs. Toss everything back together (minus the fairings) and warm the engine up.
After a brief ride around test the performance from around 8,000 RPM to red-line. If the bike pulls harder then previously then try bumping up one more jet size. Keep doing this until you feel you've lost a bit of top end power. Then drop to the jet size below that and you've completed step
1 of carburetor tuning!
