Carb Rejetting..

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Information provided by Gary...

The first step is to gain access to the carbs, which most often requires removal of the seat and gas tank 1.,

and possibly the airbox as well as the actual bank of carbs. On my long-term Bonnie we just popped the seat and tank off, and there they were. (In fact, Cook tells me that with the right tools we could have done this job without even removing the tank.) My Bonnie has Keihin constant-velocity carbs, which are pretty typical for most modern bikes. The top of each carb is held on by four small screws that must be removed carefully 2.,

so use a screwdriver that fits the screw head exactly and keep a small mallet handy in case you encounter resistance. If the screws don't turn easily, stop what you're doing and grab the mallet. Lightly tap the screwdriver into the screw with the mallet to help break loose corrosion in the threads and to secure the bit's location in the screw.

Gently remove the screws, keeping a finger on the top of the carb when you get to the last one because there's a spring underneath. Remove the top, and take out the spring 3.,

which will expose the carb's diaphragm. Reach a finger into the middle of the diaphragm and pull it out of the carb body 4..

When you lift it up you'll see the needle dangling from the bottom of the holder 5..

The needle looks almost exactly like a small nail with a tapered end that points somewhere into the carburetor.

Next, gently pull out the plastic device that holds the carb needle in place 6..

This is why we're here: Raising this needle allows more fuel into the air/fuel mixture moving through the carb (this is what to do if your bike is running lean), and lowering the needle cuts off some of the fuel (if you're bike is running rich, which isn't likely if it's stock).

To raise the needle you have to put some shims (washers made of nylon or alloy) around the base of the needle, which allows it to rest in a higher position inside the diaphragm 7..

Shims can be purchased at any hardware store. (Cook told me to buy nylon washers in size #4)

The Bonnie has standard needles, so we just put two shims on each needle to richen the mixture. In case your bike has already been fitted with a jet kit, you'll find that you can also raise the needle by using clips that attach to serrations on the needle. These serrations also allow you to raise or lower the needle.

Once you've raised or lowered the needles, button her up. Always make sure you double-check the orientation of the slide (the thing that holds the needle) in the carb body, though, as on the Bonnie, most carbs won't let you do it backward. Also, don't forget to put the spring back in the diaphragm, and make sure the top part of the spring is seated on the nub inside the top of the carb. Finally, don't overtorque the screws.

Next, fire 'er up and see how she runs. Power should be delivered nice and smooth, with no dips or hiccups along the way. See how easy that was? Now Cook says I'm ready for a valve job. I hope it's some kind of bike thing and not that scene from Deliverance he's always talking about.