Carb cleaning 101 with pics

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mrviper700

mrviper700

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Due to the recent overflow of carb related questions/problems, I see theres 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. Heres what your 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, youll 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 cant, you need to get a single strand of copper wire and carefully twist the wire/jet till it will break thru the crud. (dont use a torch tip cleaners as for 1 they dont have a sharp enuff 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 reinspect 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 orfice and squirt it in there, it should come out the front of the carb(thru the fuel screw orfice 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 flatslide 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, its located here. You will also note the large plastic housing below the jet , this keeps fuel around the main jet so the fuel doesnt run away from the jet making for a lean condition on take off, 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 carefull when you tighten down the jets, they are only brass, as are the nozzles in which the main jet screws into. Dont 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 wont have any problems here, but sometimes the needle and seat will need replaced due to it leaking or damage. there is a pin thats pressed into the 2 tangs on the carb, be very carefull 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 everytime 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, your gonna 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 recieves, make sure the carb cleaner and air go thru the carb and are unobstructed. These are also brass so dont be the hulk 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, theres not alot of parts to deal with. This is just a basic explanation of a yearly carb clean, I didnt get into removing the needdles and setting them, I will try and keep this basic because this is all thats 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 your starting off the season with clean carbs and the engine will run as it should once you install fresh fuel! Dont take the sled out for a first ride on gas thats been in there for a year, use fresh premium gas to top it off. Most all burndowns will be at the beginning of the riding season and the cause is usually dirty obstructed carbs and bad gas, avoid the burn down blues and enjoy your sledding season! :2strokes: :wel: :winterrul
 
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AWESOME post Don.!!!!!!!!!

This is truly a dummy proof description for carb cleaning to anybody thats not even a novice tuner.

When you get time and the chance, it seems there are a ton of issues with blown motors due to crank seals this year and I dont believe alot of people have a clue where to start on that issue, so maybe do a step by step disassemble with pictures and rebuild??
 
So Don.... 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 a issue once on a round slide where the needle jet was dirty. Took a lot "thinking" to finally find that one.

Would appreciate your thoughts on this.

Thanks

Exciterfan

P.S. After I cleaned my first Mikuni, I swore I would never touch another Tilliston again.
 
Wow, that is a great write up. Now if I get some free time soon I will be following this step by step. I always wanted to clean my carbs but I never had the guts or information on how to do it. Thanks!
 
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, 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 its not all green and corroded, where it would be neccessary to disassemble the entire rack and clean it then, thats a rare case.
90-95% of the time it will be the pilot circuit thats 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!
 
Hey Mrviper700, do you have to take the carbs completely out or can you do them right in the sled? Or is there a way to take them out without making a mess with gas and what not?
 
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, your gonna 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, its 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 plierw from marring up the hose. You can also use golf "tee's" to block off the hoses, they work great.
 
Awesome, good info guys. Maybe I will tackle this on friday night since the damn trails dont open up til the 10th, and we do have a good amount of snow with the possiblity of more tomorrow night into friday.

I will post some pictures in the working log to show you guys what mine look like, i doubt the guy before me ever cleaned them.
 
Great tech post

MRviper, That was really great! Pictures and good explaination of all parts. For those of us that only work on sleds part time thats better than any manual if bought! I always use the tech write ups here it's a great refresher each time ! I have printed each one and put into a binder for quick referance. Thanks Again
Blue
 
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