I set out to replace the idle jet on my LX150 today. For those who don't know, the N.American version has a smaller idle jet than can contribute to the hesitancy when starting off of the line. I wanted to swap out that one and replace it with the 38 jet offered by Motorsport Scooters here
I took some photos of the process, and posted them on Flickr. Unfortunately, I cannot figure out how to properly embed them into this thread. Instead, you can access the photos here. There are four, but only a couple are needed for this discussion, and I'll reference them below.
The tools needed are simple: a small flat head screwdriver, small Phillips head screw driver, and a rag. Of course, you need the 38 idle jet. You may also want to purchase the carb air/fuel mixture adjustment tool in case you need to reset the carb. I have one, but haven't yet used it. That will be in another step.
The first thing you'll notice when you look down at the carb is that it is held by two large hoses/connectors. You need to remove these by undoing the hose clamps and gently twisting them off. I found the hose towards the front of the scooter to be much easier to remove. The one in the rear took a lot more effort. Be careful that you don't pull so hard that you inadvertently stretch or break a line.
Once you have both hoses off, place the rag over the top of the carb. This will be needed to catch any gas that flows out once you turn the carb over. Then gently turn the carb over. Make sure that you do not catch any other lines in the process. You'll soon see that the carb can only be turned in one direction easily. For me, I was standing on the left side (as you straddle the scooter) and twisted the bottom towards my side and the top away from me.
When it is turned over, you'll appreciate having used the rags! On the bottom of the carb is a cover that is held on by four small Phillips screws on the corners. Remove these. Once off, the cover can be removed. I found that I could just move it out of the way, rather than take it off all together.
With the cover off, you'll see the idle jet sitting in the recessed middle receptacle. Use the small flat head screw driver to remove it. Carefully thread in and tighten the 38 idle jet.
Replace the carb cover and tighten the four Phillips screws. Carefully turn the carb back to its original orienation, making sure that you are not catching any other parts or lines. Then replace the two main hoses/connections. Once tightened, the carb is secured.
You should then be able to start it right up! I found that unlike the original idle jet, I didn't need to give the scooter any twist of the throttle to start it. Rather, it just fired up!
I also noticed that my idle is a little high, so will be adjusting the air/fuel mixture when I have a spare moment.
Hope that you have luck in making a similar change.