Raptor 250 GYTR Ltd. Mod Update Part 1

After 1 race and hours of extensive seat time, my Raptor 250 was due for a few upgrades.

In my previous blog I talked about my first experience in throwing a leg over the fun and nimble Raptor 250 and even my first race aboard the machine. Over the past two months this quad has gotten plenty of use by both myself and Adam Campbell when we go out to the track on practice days. With my regular race machine being torn down for maintenance before next years race season starts, my new practice machine was ready for a little TLC itself.

The stock plastic was definitely showing some wear and tear, the filter needed maintenance and I wanted to setup the quad a little more to my liking. With this in mind I decided to make a few calls and get some parts on their way to me. Since the quad was already outfitted with a few GYTR parts, I chose to add to the list with a graphics kit, K&N style airfilter, outerwear, aluminum filter flange and jet kit complete with new needle. In the handling department I opted to order a set of my favorite FLEXX handlebars and mount them to the stock steering stem using the new Rox anti-vibe handle bar risers.

First on my agenda was to install the graphics kit. This kit consists of the front nose, tank panels, two front fenders and 4 rear fender pieces. Not that graphics kits are difficult to install but these went on very easily and give the macine a clean even sportier look. Now was time to gain a few more ponies by eliminating the foam filter and installing the high flow unit I ordered up. The GYTR complete exhaust system makes a good amount of power, but by installing a higher flowing air filter, leaving the air box lid off and rejetting the stock carburetor i'm sure that there is plenty of extra power to be had.

The I opted to install the aluminum flange in the airbox before anything because it seemed to be the easiest to quickly get out of the way. Not only does this flange allow you to run a K&N style filter in the stock airbox, but it also does away with the restrictive anti-backfire screen that sits behind the air filter. Simply remove 6 nuts, pull and toss in the trash. The new flange gets bolted right back into place with almost no hastle. With this done, the outerwear went onto the filter as the filter was clamped into place.

This next part ended up being a little more complicated than I had expected. Jetting of carburetors is nothing new to me since i've done it for years on my own machines as well as customers machines at my previous job. The vaccum slide carb that is used on this machine is tightly tucked in and takes a bit of effort to remove, but once you've had to do it once or twice it becomes easy. Now before I get into further detail, when I asked for these parts to ship from Yamaha I had requested to receive the appropriate jetting for the exhaust and air filter with the lid removed. What I received was a GYTR jet kit which came with 5 main jets that ranged from 130-140 size main jets, a 27.5 pilot and an adjustable needle.

I pulled the float bowl off of the carb at the work bench to find a 133 main and a 25 pilot. I figured this kit was to be used in conjunction with the filter I requested and the instructions called for the 135 main jet. Since I will be running the lid off of the air box I opted to run the larger 140 main and changed the pilot and needle to the recommended specs. The carb went back into the frame, the fuel line was connected and I fired up the engine to make sure everything was ok.

What I found was that the engine seemed to be starving for fuel as soon as I started giving any kind of throttle. Simply opening the choke as I cracked the throttle proved the problem as the engine revved how it was supposed to. A few quick calls to see what other companies recommended as base jetting for their exhaust systems let me know that the GYTR kit was waaaaaay off. After a trip to the local ATV dealership, the machine ended up with a 162.5 main jet and seems to be running great.

Here are some pics of the project and parts that were installed. I'm still waiting on my bars and risers so as soon as those come in, you'll see and hear about it. Feel free to let me know what you think about this project and stay tuned because i'm going to be building an '09 KFX 450 soon.