Why Re-Jet, you ask?
It may be necessary to change the size of the jet in your carburetor. Perhaps the weather has changed, the altitude id different, maybe you put on a different exhaust pipe. Things like this can cause your motor to run "lean" or "rich". Then your motor will run like crap, or even seize. That's bad. an easy way to know if your 2-stroke engine is running lean or rich is to take out the spark plug and look at the electrode. If it looks white, you're running lean (not enough fuel). If it's black, your running rich (too much fuel). You might also notice that you're running lean if you give full throttle and the motor seems to not want to respond. If you're rich, the motor will be boggy and make a noise like a sick goose (referred to as 4-stroking). anyways, let's jet your bike.
I'll show you how to do it.
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Step 1: What Choo Need
You'll need a big flat head screwdriver, a tiny flat head screwdriver, a 14mm wrench, a rag and some jets.
Step 2: Turn Off the Fuel...
You should have a petcock valve with a fuel line coming off it. Turn that off. I'm not sure which way is off on your bike. If you know, the great. sometimes they don't even shut off because they are all crusty. If you know which way is off, then turn it off and pull off the fuel line. You may want to have a rag ready in case it spills some gas.... If it won't shut off, try jamming a pencil up in the fuel line. That might work?
Step 3: Remove the Carburetor
The Bing carburetor has a flat head screw which clamps it onto the intake manifold. Loosen that screw and wiggle off the carburetor. It might need to be rocked from side to side as you pull it off.
Step 4: Unscrew the Float Bowl
If you have a 14mm wrench, use that to loosen the float bowl. An adjustable wrench will also work. Once it's loose, you should be able to unscrew and remove it by hand. It might be full of gas, so hold the carburetor as straight as possible and have your rag handy.
Step 5: Remove the Jet
In the center of the carburetor is the jet. It's made of brass and is kinda delicate. Use a SMALL FLAT SCREWDRIVER to remove it. Be sure the screwdriver fits properly, or you'll mess up the jet. Seriously. NOTE, there is a chance that the jet will come out attached to a tube. No worries. Once it's out, use pliers or something to hold the tube, then remove the jet.
Okay, time to put in your new jet. There's going to be a tiny number stamped onto the jet. Good luck reading it. If you are running lean (your spark plug is white), then your new jet must have a higher number than what is stamped on your old jet. If you are running rich (your spark plug is black), then your new jet must have a lower number than what is stamped on your old jet. How much higher or lower? I have no idea. You're going to have to start trying jets until you find the right one. As a general rule of thumb, you should start with a jet that is too big, so your motor "4-strokes" (that sick goose noise) and then start working your way down until it stops 4-stroking. Then fine tune.
Step 6: Take Your Top Off....
On the top of the carburetor are 2 small flat head screws. Unscrew them. The top might pop off, as there is a spring under there. Don't let everything fly away. Gently remove the top. Your choke slide will come loose, so grab it. as you hold the top, push the throttle slide up until the throttle cable pokes out the bottom, wiggle the cable over to the other hole and pull the cable through the throttle slide. I don't have a great picture of this, and it's a pain in the arse, but you should be able to figure out what I'm talking about.
Step 7: Needle Adjustment
Once the cable comes out, the whole assembly comes apart. when the spring is free of the throttle slide, you can remove the needle. On the needle will be a clip. we want to set this clip on the bottom notch. If it's already there, great, you can put everything back together and move onto the next step. It it's set anywhere but the bottom notch, use a pair of pliers to pry it off and set it on the bottom notch. Now put it back together. Getting the throttle cable through that hole and over into the next one is a hair-pulling job that requires patience and cursing. Take your time and do it right, or else.
Once it's back together, you need to look into the top of the carb for the little bump that will line up with the valley that runs on the side of the throttle slide. The throttle slide needs to be put in so that these line up, or else it won't go in. Once everything is together and the top is screwed back on, pull the throttle control and look through the throat of the carb to be sure that everything is moving properly. It is? Great.
Sooooo, Put in a big jet. Put it all back together and start the motor and ride. It 4-strokes, right? Good. If not, put in a bigger jet until it does 4-stroke. Once it's 4-stroking, start working your way down the jet sizes until it stops 4-stroking. What's that? It finally stopped 4-stroking? Okay, Now we're going to put back the last size jet that you took out. take it back off, open it up, put in the jet, take the top off again and move the clip up 1 notch on the needle. This is the fine tuning part. Put it back together and ride the bike again. still 4-stroking? Take it apart, move the clip up another notch, reassemble, ride. If you manage to move the clip all the way up the needle to the furthest notch....
Take off the carb, put BACK IN the next size smaller jet, take off the top, move the clip BACK UP ALL THE WAY TO THE TOP of the needle, put it back together and you're done. The motor should no longer be 4-stroking.
That was a total pain in the butt, wasn't it. Yes, it was.
One thing that I forgot to mention is, it's kinda hard getting the choke slide to fit back together when reassembling the top portion. What I do is, line up the throttle slide with the bumb and start it in 1/2 way. Put the choke slide in its track THE RIGHT WAY, hook it to the choke rod and then put the top on. Be careful not to tear the gasket. Sometimes the throttle cable pops off and you need to take it apart and try it again.
After you've done this a few times, it gets much easier.