Jetting: Part 1

[jonathan180iq]

I'll be using this post to follow my attempts at jetting a GZ250 without a jet kit. This will not require any type of drilling or permanent alterations, aside from drilling out the idle mixture screw cover, which does nothing to affect the fucntion of the carb. You can consider this as a HOW-TO as well as a MODS post.
Hopefully, upon following my posts, you'll be able to avoid any kinks that I come across.
By the end, I suspect that we will have a total jetting HOW-TO with a total parts cost of under $20, minus the pod filter.

7-18-07:
The main jet in the 2006 model is a 120. The main jet size varies depending on the model number on the side of the carb (this info can be found in the service manual) and the year of prodcution.

Today, I went over the my local Suzuki shop and asked for the 3 next sizes up.

122.5, 125, & 127.5

At $3.00 a pop, this is not going to burn anyone's wallet.

Since the main jet is the first thing that needs to be adjusted for proper jetting in the other ranges, this is the first place to start.
When jetting, it is important to find the main jet that gives the BEST pull under 3/4-full throttle. I did not say good pull. I said best, given the options. Discovering which jet gives the best performance requires getting several jet sizes and testing them on the open road. This will require installing a new jet, testing it, coming home, pull the carbs and repeat. If you are switching over to pod filters, this will be LIGHTYEARS easier, as the removal of the airbox will no longer be necessary.

I purchased the three increasing jet sizes to have a pretty wide field. In a perfect world, I should have also bought the 3 lower jets and maybe even a 130.
However, I highly doubt that I will need a smaller main jet, as my current factory jetting is pretty spot-on and I feel that a 130 would be too rich.

Once I do some work this weekend, I'll post my results and then we will move on to the needle adjustment.