Carb cleaning 101 with pics by MrViper700

 

Due to the recent overflow of carb related questions/problems, I see thereís a bunch of people intimidated by simply cleaning the carbs, they are simple inside and maybe some can see how easy it is to maintain your sled and prevent all the "just out of storage" running problems. Hereís what youíre looking at and what to look for and clean.

This is what you will see when you remove the 4 Phillips head screws holding on the float bowl.

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This is the pilot jet location

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This is your main jet location

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This is where the fuel screw is located

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your first step is to remove the pilot jet and the tube, youíll want to clean out the pilot jet and holding it up to a light, you should be able to see light thru the jet, if you canít, you need to get a single strand of copper wire and carefully twist the wire/jet till it will break thru the crud. (Donít use a torch tip cleaners as for 1 they donít have a sharp enough tip and 2 they will make the jet bigger with the side teeth on them once you get it thru the hole)

Then clean well with carb cleaner and reinsert to see light thru the jet. The pic shows the jet removed. Notice all the small holes on outside of it as well.

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Once you have the jet cleaned, you want to insert the hose of the carb clean can into the pilot jet orifice and squirt it in there, it should come out the front of the carb (thru the fuel screw orifice feedhole), if the fluid does come out, this means the carb has no restriction in it and your good to go.

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Next you can remove the fuel screw and spring assembly, and inspect it, clean it. You will find most of the time this to just have some crud build up but not be blocked, this is also the time to reset your fuel screws if you have had previous idle hang problems commonly found on Yamaha sleds with the flat slide carbs. The fuel screw setting are from a LIGHTLY seated(in all the way) to turns counted going counter clockwise, so if your setting was for example: 1.25 turns, that means all the way in to just barely snug, then turn the screw driver 1 complete 360 degree revolution and then a quarter of a turn More, see its simple!

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Time to clean and inspect the main jet. Itís located here. You will also note the large plastic housing below the jet. this keeps fuel around the main jet so the fuel doesnít run away from the jet making for a lean condition on takeoff, jumps, bumps, etc. This just sits on the jet nozzle, the jet nozzle is the brass item you will see when you remove the main jet and plastic shield. Be careful when you tighten down the jets, they are only brass, as are the nozzles in which the main jet screws into. Donít get carried away tightening them.

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Moving right along we come to the needle and seat and the float, most times you wonít have any problems here, but sometimes the needle and seat will need replaced due to it leaking or damage. there is a pin thatís pressed into the 2 tangs on the carb, be very careful when trying to remove this, do not ever strike it with something to remove it as you can easily break off the cast tang from the carb body and then your screwed.

This is also where you will check your float height, this is from the bowl surface to the metal float arm, there are specs in the tech section for your measurement, but a good rule of thumb that will get you thru almost every time is adjust it till its parallel to the carb float bowl machined surface. You bend the little tang on the float arm that contacts the needle assembly. you can bend it with a penlight screwdriver-gently!

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lastly, youíre going to want to squirt carb cleaner and air thru the air bleeds in the back of the carb, you will also see this is where your air jet is, there is no adjustment for them, they are screwed down tight, these control how much air the idle and low speed circuit receives, make sure the carb cleaner and air go thru the carb and are unobstructed. These are also made of brass so donít Ďbe the hulkí and strip them out.

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Now all you have to do is reassemble it, the way you took it apart, if you clean each circuit as you go, thereís not allot of parts to deal with. This is just a basic explanation of a yearly carb clean I didnít get into removing the needles and setting them. I will try and keep this basic because this is all thatís needed for a carb clean; the rest comes in more of a tuning set up. I will make a tuning set up later for this forum, showing how to change the needle setting and plug readings etc.

Good luck and clean those carbs, it should be done EVERY year, this way you know youíre starting off the season with clean carbs and the engine will run as it should once you install fresh fuel! Donít take the sled out for a first ride on gas thatís been in there for a year, use fresh premium gas to top it off. Most all burn downs will be at the beginning of the riding season. The cause is usually dirty obstructed carbs and bad gas, avoid the burn down blues and enjoy your sledding season! http://www.totallyamaha.net/forums/images/smilies/2strokes.gifhttp://www.totallyamaha.net/forums/images/smilies/welcome.gifhttp://www.totallyamaha.net/forums/images/smilies/winterrules.gif

 

 

 

Question #1

What about cleaning the needle jet on a flat slide? It comes out of a round slide carb very easily, but it doesn't look like that would be the case on the flat slide.

I've pulled the needle jet up (once the main jet has been removed) and sprayed carb cleaner on it, but it looks like you'd have to pull the needle right out to actually remove it. Can you get away without cleaning the needle jet on a flat slide? I had an issue once on a round slide where the needle jet was dirty. It took a lot "thinking" to finally figure that one out.

I would appreciate your thoughts on this.

Thanks

 

Answer #1

Exciter fan, you can cheat by doing it this way, you simply remove the main jet, and then open up the sled throttle linkage all the way and block it open with a screw driver handle. The needle jet nozzle will then come up out of the well and you can blow carb cleaner thru it. You can NOT remove it entirely unless you remove the slide of course, but you can get it clean like this if itís not all green and corroded, where it would be necessary to disassemble the entire rack and clean it then, thatís a rare case.
90-95% of the time it will be the pilot circuit thatís the culprit to running problems, the rest goes to the needle valve, they get stuck closed or open from the buildup of old gas and the heat from the sun during storage causes the gas to revert back to crude oil and goop!

 

 

Question #2

Do you have to take the carbs completely out or can you do them right in the sled?Is there a way to take them out without making a mess with gas and coolant?

 

Answer #2

I would advise removing them from the sled, as if you drop something like the jets, screws, etc. while doing this in the engine bay, youíre going to be making up new swear words!!

Once you remove them just tip them over a bucket and the gas will run out the vent hoses, itís not that much.

I just plug the coolant hoses with a rag over them and a pair of needle nose vise grips gently pinching them closed, the rag keeps the pliers from marring up the hose. You can also use golf "tees" to block off the hoses, they work great.

 

 

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