Which setting do I use for the needle in my carb?

You didn't say what year or model your bike was but if it runs better when it's cold than it does when it's hot, this is an indication that it's running rich. Does the bike start up and idle without the use of the choke or very little use of the choke? If so, another indication that it's rich. Take the air filter cover and element off, leave the backing plate on, and take the bike for a ride. If it runs better, yet another indicator that it's running too rich. What type of carb is on the bike? This is unusual as most bikes,unless they've been rejetted, are jetted lean and have a nasty habit of spitting back from the carb.

Steve

Your bike is not equipped with a "choke" per se. It is equipped with an "enricher" circuit. Although both systems are meant to provide a rich mixture with which to start a cold engine, they do this it completely different fashions. If you were to ride the bike with a "choke" partially on, it would run very rich. But, once you crack the throttle plate open on an "enricher" equipped carburetor, the enricher is rendered inoperative. An enricher only works when the throttle is fully closed.

If you're running rich and fuel is splattering down the right side of the bike, you've got other problems in the carb. I would suspect that your needle and seat is not sealing like it should for one reason or the other. If the bike sat up for a while, it could have some residue on the needle and seat left from the gasoline evaporating or something. I'd go purchase a can of carb and injector cleaner and pour some in the fuel tank. Do not allow any of this to get on your paint. Try that for a tank full if you can. If that doesn't work, the carb needs to be taken off, stripped down, and thoroughly cleaned inside. Maybe install a new needle valve. The seat is not replaceable in the original carburetor.

Good Luck
Steve

Use adjustable needles.there should be five slots start in middle and get bike running.then adjust according to if bike is running rich or lean.

There are many reasons that an engine can run too rich, and the place to start is to be sure that running rich really is your problem. Running rich means that the fuel:air ration in your cylinders is too high. That means that there is too much gas and not enough air getting to the cylinder. The easiest way to verify that your bike is running rich is to run the bike for a little while, then pull out the spark plugs and take a look. If they are covered with dark black carbon build up, then your bike is in fact running rich. Be sure to check all four plugs to see if all your cylinders are rich or just a few of them.

If you are running rich, then you almost certainly have something improperly adjusted in your carburetors. If you are not the kind of person who likes to work with small parts, and keep your workbench organized, then working with carbs is probably not for you. But if you do like to tear things apart and get to the heart of them, then press on and we'll have your bike running right in no time.

The most likely cause of running rich is that your bowls are flooded. the bowl is the bottom part of the carb where the gas sits, and your bike has four of them. each one has a flat-head screw on the bottom side, and a nearby nipple where you can connect a piece of clear hose. Connect a clear plastic hose to the nipple, and then use a flat screw driver to loosen (but not remove) that screw. When you loosen the screw, gas will flow from the bowl into the hose. Hold the hose up to the side, and the gas level should be about even with the seam where your bowl connects to the body of the carb. If the gas level is any higher than that, then your bowls are flooded. That means that your float needle seats are not sealing correctly inside the carbs. This can be caused by having pieces of debris or rust clogging the float needle seat, or by having old worn out float needles. you can remove the carbs from the bike and check each float needle individually. The rubber tips should be cone-shaped, and come to a nice point. The brass seats should be clean and free of debris. Clean everything out with carburetor cleaner from your local napa or auto zone, and put it back together. Be sure not to get carb cleaner on your float needles or other rubber parts though as it will dissolve the float needles. If your float needles are worn, then they will need to be replaced. If the inside of the carbs are just dirty or gummy, then clean them out until they are nice and clean.

If your bowls were not flooded, then you may have a problem with the fuel jets. A lot of people take carburetors apart to clean them, and get the little brass jets in the wrong place when they put it back together. Each jet has a tiny number inscribed on its top surface. The bottom side of the carburetor (inside the bowl) has two jets that look similar and have identical threads, but the holes that go through them are not identical. The main jet is the one that goes right in the middle of the carb and screws into the brass needle jet. It's size is around 120. The pilot jet goes off to the side and its size is around 35. The threads on these jets are identical, but if you get them in the wrong place, then your bike will always run rich -- especially at idle. Check all four carbs to be sure that the jets are correct. Another good indication that you have the jets switched is if you can easily start the bike without choke even if it is dead cold.

If both the jets and the fuels levels look good, then you may have more serious problems. But those two are the most likely cause. Those are things that are easily overlooked by first-time mechanics, and they are pretty easy to fix if you have patience and are willing to deal with the small parts that go inside of carburetors.

Good Luck,
-Josh

dont move the needle position, hopefully you drained all the old gas, get a can of carb cleaner at the parts store,remove bowl plug under carbs stick nozzle up and spray, should be a idle adjustment screw under carbs turn 1/2 turn, also when you go to to the parts store get a can of fuel injector cleaner and marvel myster oil and put in tank. then take bike for a nice long ride

Your lower rpms are controled by the mixture screw, pilot jet, accelerator pump and the slide needle. So your problem is probably in one of these-though racing 4 strokes are known to have a little stumble at the bottom, but not what you're describing. I'll have to assume the shop has the pilot jet clean and the mixture screw adjusted properly.(roughly 1.5 turns out)

First, check your accelerator pump. Remove the carb enough to be able to look inside the throat, but leave the cables hooked up. Work the throttle a few times and make sure that there is a small squirt of fuel in the throat of the carb each time you twist the throttle. If not, your accelerator pump is clogged or damaged.

If everything is fine there, the next likely problem is the needle adjustment. It's mounted in the slide. Once you remove the needle, you'll see a small clip around it. Try moving this clip up one notch. This will lower the needle and slightly delay the fuel feed from the main. If this fuel comes in too soon, it will cause a way rich condition and cause a bog off idle.

Outside of carb issues, valve adjustment(too tight) can make for a rough idle and hard starting.

Stock it would be around 2 turns out.

These bikes shipped with only one jet needle (unlike other Yamaha's) the bike's factory jetting is 45 pilot, NBKF needle on the 2nd clip from the top, and 138 main. This bike tends to run a little rich off the bottom, so I'd recommend running a 42 pilot instead. When it's really hot out (over 90) you can run the 135 main jet.

Screwwing with carbs is fact of life with these bikes - you will have to do some tweaking no matter what.

the quick fix is to lower the needle by a notch, you need to pull the top off the carb and remove needle then raise the little circlip up to the next groove which will lower the needle and let less fuel through.
this may help some but it depends on when the bike runs rich as there are a number of jets that can be swapped to change mixture settings

Hi Chris,
You will have to recheck the float level (in the float chamber) of those two carburators, reset if necessary.
You may also have to reset the air-mixture screw for both of those carbs. Standard procedure to set htem is tighten them all the way in making sure not to over tighten to avoid damaging the sharp end of the screw, and thn to open 2 and a half to 3 turns.
You can thn reset them as the engine is running + -- either way.
Hope this helps!

sounds like its running to rich, check your air filter is clean, set your carb mixture ,
turn the screws in untill they bottom out ,but dont turn to hard !(they have a fine needle point end and are easy to break leaving the broken point inside the carb making adjustment impossible )back all four screws out 1.5 turns and start from there.run the bike and adjust from there to rich turn out to lean ( weak turn in )

www.thegsresources.com a good web site for these bikes.

good luck