Hello all, I am looking for advice on how to jet my BONE STOCK 2003 XR 650L for a little trip to Colorado later this summer. Any advice would be well appreciated.



Oh boy do I have some info for you!

Go a little beyond the jetting and you can make it into a new bike.

Here's what's become my standard 'canned' reply.

Its pretty simple, but I have to admit drilling the slide is a little nerve-wracking. Also, doing the smog block-off will stop the popping, but will not really increase the power.


There's a photo somewhere of the slide, photo section of the yahoo XRLUG site. You can do it without the photo, though.

You drill the vacuum holes indicated to 5/32 of an inch. There are 3 holes, one in the middle for the needle and 2 off to the side- drill the 2 not in the center.

THE NEEDLE: When you pull the slide, the needle is held into the bottom of the slide by a little yellow widget that you press down on and turn a little with a screwdriver or an 8mm socket. When you remove that, the needle comes right out. Notice that the needle sits in a small recessed section, a little well. Find a small washer that meets the following


1) is about 20-30 thousands of an inch thick.

2) fits fairly snugly over the needle at the thickest part at the top.

3) has the same outside diameter as the top of the needle.

You just put the needle through the washer like you would a washer on a bolt so that the needle will be raised up out of the slide by the thickness of the washer. Some have found washers like this in a kit at radio shack. I found one that I had to make a little smaller on the outside diameter in my "supplies".

If you do this, remove the snorkel, and grind off the tab on the bowl that keeps you from spinning the low-speed mixture screw around, and put in a good air filter, you'll wonder how you managed to ride the bike without these mods. If the mixture screw is out more than 2-3/4 turns, you need to go up on the pilot jet.

The suggestion to replace the screws on the carb with allen heads is an excellent one as well. I replaced the 4 bowl screws, the 4 screws in the top, and the 2 that hold on the throttle cover.

The slide gets raised when vacuum is applied at the bottom of the slide, and the holes are how the air leaves the area above the slide. Hence, the bigger the holes the more faster the air can leave.

I'm running stock exhaust, K&N filter, and run a 55 pilot and 158 main (both keihin jets from Baja Designs), and this setup is rich enough to run with the baffle out. Note that there is a 55S short pilot jet, and the 55 regular pilot jet will work but you have to trim the slosh baffle in the bowl a little, as it can move a little and partially cover the pilot jet.


PS adjusting for elevation: this might be a touch too rich at 5000', but I'm not sure what jets are avail. just under the 55/158 sizes. A touch rich won't hurt, and you can always screw the pilot screw in a little.

Also, if they're running Gasohol (90% gas, 10% ethanol) that'll make it a little leaner.

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