The end game is here. Reassembly. One step closer to a smooooooth running bike! Its going to be a big post though so let’s not muck about…
Lets start with the throttle shaft (assuming you removed it). Take a look at the photos and hopefully you can see which side the shaft slides into. From this side, install the rubber seal. Spread a small amount of grease on both ends of the shaft where it rotates in the carb body. Slide the throttle return spring along the shaft and set it up as shown at right. Now slide the spring and shaft into the carb body and make sure the spring legs line up as shown by the arrows at left.
We can now insert the rubber seal on the opposite side, the plastic washer and follow it up by installing the E clip. Be careful the clip doesn’t grow a mind of it’s own and send you on an adventure to the darkest and hardest to reach parts of your workshop floor!
Check the operation of the throttle shaft and make sure its smooth and returns effectively. If all is well then install the E clip cover and tap it on lightly with a soft faced blunt instrument. We can turn our attention to the other side of the throttle shaft again and install the Idle control screw and spring. Make sure you adjust the screw right through so it deflects the throttle shaft a significant amount. This will aid you with installing the butterfly as we shall see next.
We now need to do a bit of juggling because we have to rotate the throttle shaft to maximum open position while we slide the butterfly into the slot in the throttle shaft. Not as easy as it sounds but a bit of persistence will win the day! A set of soft jaws in a vice to (gently) hold the carb body might be a help here. It will free up a hand to help keep the throttle shaft in the wide open position. Have a look at my photos so you have the butterfly the right way round on your first try to slot it in – note the “120” indentation.
A little tip that may make the butterfly easier to manoeuvre, is to clean it with some Brasso or other polish. The smooth surface wont hang up in the slot as much and I found it can help things out, and it looks purdy!
Once you have the butterfly in roughly the right location, slowly release the shaft and try and get the whole show located properly. Resist the temptation to get rough here because the butterfly is a fairly soft material and you don’t want to damage the edges or warp it. Take your time and use a pick or scriber to gently persuade the screw holes to line up.
This is why I suggested to wind the idle screw in. It will help to stop the butterfly jamming in the home position and be a bit easier on everything. When the holes in the butterfly line up with the holes in the throttle shaft, gently insert the butterfly screws into the assembly. Don’t do them up too tight and don’t use thread locker, they are tight enough in my experience.
Now that everything is in place and tightened up, rotate the throttle shaft and make sure it opens and returns smoothly. The last thing to do here is get some strong light and make sure there is no brass swarf as a result of sliding the butterfly through the throttle shaft slot. Inspect both sides of the butterfly.
Time to move onto the pilot adjust screw, check the parts at left – the screw and its O-ring, spring, washer and another O-ring for the shaft of the screw needle. The easiest way to assemble this into the carb without potentially losing bits and/or not having the washer and O-ring seat properly, is to point the needle upwards and assemble the bits down over it in order. First the spring, washer and O-ring.
The O-ring should hold everything on the needle shaft but why risk it? Grab your carb, turn it upside down and lower it down onto the the adjusting screw and its assembly of parts – easy! Screw the adjuster gently all the way down into it’s hole until it bottoms out, then screw it out two turns – the factory spec. You will find somewhere between two to two and a half turns will be optimal when the bike is running again.
Next to go in is the emulsion tube. You have inspected the top, inner hole of the tube right? And the needle? Good, now have a look at the other end that has the thread cut into the inner part of the tube, see the slot on the outside of the tube? This section has to interface with a brass post pressed into the main jet tube of the carb body. Slide the emulsion tube in through the top of the carb and wiggle it home as shown at right.
We can now insert the “active” components into the float chamber. Start with the main jet and its’ washer. Remember you are working with soft and brittle materials here, not too tight. Install the pilot jet next followed by the fuel/float valve. If the O-ring is OK I like to put a bit of rubber grease on it to help it to not bind when you insert it. I do this on most O-rings actually, it just seems to go back together nicely without having to force the rubber.
Now the last few bits to finish off the float chamber. The fuel valve retaining bracket is next and then the plastic main jet shroud. I forgot to show the pilot jet plug in this snap (at right) but its there in the final pic after I installed the float assembly.
Slide the float valve needle onto the float tang and manoeuvre it all down into the chamber and focus on the needle going into the valve. Line the float pivot hinge up with the holes in the float posts and slide the pivot pin through both items. I use a pair of adjustable-jaw plumbers pliers to gently press the pin into the interference fit of the posts of the carb body. That’s most of the float area done, we just need to put the bowl on and screw it down. Note that the picture at right showing the assembled float chamber has the pilot jet plug installed as mentioned above.
Now I’m going to have a bit of a break from assembly talk for a moment so I can explain a huge hole in my tutorial. You may of picked it up – what about parts replacement? I have mentioned replacement of the emulsion tube and needle if they are worn but what about all the other parts of the carburettor? Surely some other bits here are consumer items? Yes, yes there are. Mostly the rubber parts – O-rings etc..
I have left consumable replacements out of this blog for the moment because it is a whole new discussion. If your carb is in reasonable condition then you can re-use most of the rubber components. If your AG200 has been sitting for a long time and/or it’s an older model, then there is a better than average chance that all the rubber components (maybe with the exception to the float needle valve) in your carb are shot.
So what can you do if you have dodgy rubber bits? Wait for my next blog! I am researching stuff at the moment and will have options to discuss but if you’re in a hurry then I’m afraid its off to your local Yamaha dealer to get pillaged!
Back to the carb…time to screw on the float bowl. Nothing hard about that except you can use the old gasket if its still in good shape and take note that one screw has a loop for the float chamber vent hose. Have a look at some of the proceeding pics and you will see at what corner this loop is attached to. You can see two bits sitting in the middle of the gasket at left, disregard the pilot jet plug (you should of already installed it!) but you better put the float bowl drain screw in!
That’s the bottom of the carb done, spin it over and now we turn our attention to the top part where the slide and diaphragm go in. Before we can install the slide assembly we need to screw in the pilot air jet as shown at left. Now we can assemble the slide. Something else I probably should of mentioned earlier in my “carb cleaning” series of blogs is that I don’t clean the slide or diaphragm. Well I don’t clean it in respect to chucking it in an ultrasonic bath or drown it in carby cleaner! I find that the diaphragm is a pretty delicate thing so I just clean it and the slide down with a rag and maybe blow a bit of air down the slide to clean up the area where the needle goes.
The needle assembly needs to be assembled before it can go back in the slide. Check it out at right, the plastic washer with the alignment pin goes UNDER the E clip (with the pin facing down or facing the tapered end of the needle) and is slid on from the tapered end of the needle. The other plastic washer fits on the the top of the needle on the other side of the E clip. The spring then fits over the washer. Using your third hand ( 🙂 ), insert this assembly down into the slide.
This little pic from the manual probably best shows how the needle assembly has to align into the slide. Once you get all the bits together into the slide, gently spin the needle until you feel the pin and hole align and the needle will drop a few more millimetres into the slide. Now you can carefully drop the needle retainer plate down into the slide and insert the two Philips screws to hold it in.
Now we can slip the slide assembly into the carb body taking note of the alignment notch for the outer rubber ring of the diaphragm. Install the slide spring into the slide and install the diaphragm cap taking note that the spring stays even and the indent in the cap faces the airbox side of the carb. Do up the four screws in the cap and you’re all done.
The lucky last bit to install will be the throttle cable bracket. It’s a pain to do all the other jobs to the carb with this thing on so I leave it ’till last. It can be a pain to get back in because you have to turn the throttle shaft a bit to allow the bracket access to its’ lower locating pin, but it will fall into line eventually and you can then screw it into place.
Move the slide gently up in the carb with your fingers and it should smoothly return when you release it. Don’t forget to back off the idle adjust screw as well. Apart from that you are ready to go! You could hook up the fuel to it to make sure the needle valve is working OK. You could also check the float level as described in the manual. Apart from those options, install the fuel line, overflow and vent hoses and you can get it back into the bike and see how she goes.
What an epic post! Now taking donations! It feels good to get it all down though and hopefully it will help owners with probably the most common reason for AG200 stoppages. I know I may of left some people hanging a bit with the parts replacement bit to come, but I think that once I have it down people wont care about the order of things that much. And by the way…once this has all been done, don’t be tight and neglect to install a good filter! It defeats the purpose of all this hard work.