Uncorking the XR650R
From the factory the Honda XR650R is a bit congested. To comply with emission and noise regulations in the United States and other parts of the world, the XR650R intake and exhaust system was buttoned up. To make the bike run optimally and produce the power it was designed to, you can Uncork your XR650R.
HONDA DISCLAIMER: This is only for closed course competition and will void your warranty.
Ok, realistically, every XR650R should have these mods done. Everyone does them – it increases the grin factor and makes your bike much more sweetly.
The majority of XR650R’s out there today have already been uncorked, but if yours hasn’t here are the simple procedures.
Step 1: Remove the airbox intake baffles.
The airbox has two baffles, or restrictor plates on the back side of it. These are designed to inhibit air flow and thus they reduce power. Remove them.
Step 2: Replace the Muffler Baffle and Tip
The baffle in the muffler is flanged to restrict airflow. To get optimal flow and let your XR breathe you have two choices. One is to replace the exhaust tip with the HRC unit (part number 18317-MBN-640). The HRC unit has a 1.5″ opening and hardly any internal baffling. The other option is to drill out the flange in the stock unit. A 2″ hole drill will do the trick. Just run it straight into the rear of the muffler.
The end result of these two options is essentially the same, though the HRC will be a bit louder by comparison.
Step 3: Remove the Restrictor Plate on the Carb Intake
Remove your carb. For carb removal instructions visit the XR650R Carb Cleaning page. Between the carb and the engine you will find a restrictor plate. It is obviously designed to restrict flow. Again you will have two options. You can replace the part with HRC part number 16211-MBN-640, or you can drill out the stock unit. The end result is the same.
Step 4: Rejet
Now that the intake and exhaust is opened up all you have to do is rejet your carburetor. You’ve got lots of extra air flowing through the engine now, so you need to richen up the carb to provide extra fuel. If you are unfamiliar with the XR650R carb you can use this as a reference: XR650R Carburetor Exploded Diagram
- Replace the main needle with part number 16012-MBN-641 which is a B53 needle
- Replace the main jet with part number 99101-357-1750 which is a #175 (if you are above 3000 feet you may want a slightly smaller jet)
- Replace the pilot jet with part number 99105-MBN-0680 which is a #68s
All done! Now your XR650R will rip! Get out there and ride!
Some people will drill holes in their left side cover to expose the air filter. This improves intake flow even further, however I prefer to keep the sidecover in tact.