Rejetting your Yamaha V Star 650 motorcycle is a fairly simple task that can be accomplished in a single afternoon. The V star is a V-twin motorcycle that provides loads of power, but some enthusiasts are always looking for a bit larger "kick in the trousers." Rejetting alone will not add horsepower, but if you have added a free flowing exhaust or a larger intake manifold rejetting your bike could make a world of difference. Rejetting the carburettors allows more fuel to mix in with the air brought in by a larger manifold or a free flowing exhaust, thus giving an increase in horsepower. Rejetting is a simple process that consists of simply buying a new set of internal jets and replacing them.
Choose which set of jets you need to purchase. The link at the bottom of the page provides a table of a variety of modifications and the jets that need to be ordered for each scenario. If your particular modification is not listed, you can check with the manufacturer or with repair forums online to see if anyone has rejetted following a modification like yours before. If not, you will simply have to pick the modification that is closest to the mod that you performed, and use that set of jets to see if there is a difference.
Turn the gas off and remove the gas hose going into the carburettors by sliding the end of the hose off of the petcock.
Remove the float bowls by unsnapping the holding wire and sliding it out of the way. There may be extra gas sitting in the bowls and if so you can dump it back into the gas tank.
Remove the jets located inside the carburettors by unscrewing them and replace with the new set of jets. Replace the float bowls and snap the holders back into place.
Adjust the limiter screws on the outside of the carburettors to their furthermost setting and then start your bike. As it idles, adjust the screw until it runs smoothly but not above a few thousand RPM at idle.
Take your rejetted bike for a test ride.
Some bikes have brass plugs covering the idle adjustment screws. If this is the case for your bike you will need to remove them by threading a screw into the soft brass and pulling the plug out.
Be careful when removing the float bowls to not flip gas up into your eyes. Wear goggles and gloves when performing this portion of the install.