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Hi this is my first time on this forum. I have an 1981 ET250 single cylinder. Is anyone extremely familar with the carb that is on these sleds? It has no float or bowl. It has a fuel pump built into the carb. The problem is I can't make the thing run. It will run if gas is sprayed down it's thoat. The carb is getting fuel, the carb has been kitted. The needle valve is free the passages are clean. BUT in the main part of the carb, Right in the very center, only to be seen when carb is apart, there is a little plug (car mechanics would call it a limiter cap, and it also looks like a tiny frost plug). This plug is rusty and I need to know what is behind it. It seems to line up with the brass venturi in the thoat of the carb. What is under that cap? and if it is dirty under there would it prevent the snowmobile from running???
 

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Hi this is my first time on this forum. I have an 1981 ET250 single cylinder. Is anyone extremely familar with the carb that is on these sleds? It has no float or bowl. It has a fuel pump built into the carb. The problem is I can't make the thing run. It will run if gas is sprayed down it's thoat. The carb is getting fuel, the carb has been kitted. The needle valve is free the passages are clean. BUT in the main part of the carb, Right in the very center, only to be seen when carb is apart, there is a little plug (car mechanics would call it a limiter cap, and it also looks like a tiny frost plug). This plug is rusty and I need to know what is behind it. It seems to line up with the brass venturi in the thoat of the carb. What is under that cap? and if it is dirty under there would it prevent the snowmobile from running???[/b]
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Does it run at speed and not idle? If so, look at the top of the carb. If you see a "T" shaped plate with a single screw, there's a good place to look. Under there are prolly 5 Small holes into the throttle bore. Some or all may be plugged. Off to the side you'll see the low and mid range jets. Make sure they're clear. Is there a bolt with a nut up through the bottom of the carb.? This sets the fuel level, which can be viewed in a little vertical pipe on the clutch side of the carb. When the motor is off, take the cap off the top of the pipe. The fuel needs to be around 1/4 below the two bosses that hold the pipe upright.
 

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Discussion Starter · #4 ·
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WOW I finally found someone who is familar with this carb. I solved my problem but I am embarrased about what it was. I had the crank case line and the fuel line mixed up. Hey I'm an automotive mechanic what can I say. It still won't start but it is definitly getting fuel now. I did check those tiny ports under that cover and one was plugged but not now. Now it appears to be getting too much fuel. I have asked many people what that "air vent pipe" is for. (Air vent pipe is what Yamaha calls it) no one had a clue. I took the little cap off and the fuel level was about 1/4" from the top of the pipe which is quite high right? So could this make the engine flood? I'm so thankful for someone that knows about this carb. COOL
 

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That's definitely too high. Now I know your carb looks like mine, look closely at how the pipe is attached. P.S> DO NOT LOSE THAT LITTLE COVER FOR THE PIPE!! It's screwed on at the bottom, and about half way up, passes between the metal "dots". The fuel needs to be at or below this level. To adjust the level, loosen the locknut at the bottom of the carb, and turn the bolt. You'll need 2 12mm wrench. It shouldn't be real tight. Be careful with this adjustment. I've been down to one flat side at a time on the head of the bolt, if you understand what I mean.
Have you ever been to a store and saw an item with a cardboard tag tied to it with a piece of wire? That's referred to as tag wire. Find some.
In the meantime. The low speed jet (toward the top of the carb on the clutch side) needs to be about 1-1/4 turn out to start. You can take it all the way out and see that the passages inside are clear. Don't lose the spring.
I find a source of compressed air and a blow tip attachment are as important as a screwdriver and a wrench when it comes to these carbs.
BTW. it's a KEIHIN carb. :biggrin:
 

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Discussion Starter · #6 ·
That's definitely too high. Now I know your carb looks like mine, look closely at how the pipe is attached. P.S> DO NOT LOSE THAT LITTLE COVER FOR THE PIPE!! It's screwed on at the bottom, and about half way up, passes between the metal "dots". The fuel needs to be at or below this level. To adjust the level, loosen the locknut at the bottom of the carb, and turn the bolt. You'll need 2 12mm wrench. It shouldn't be real tight. Be careful with this adjustment. I've been down to one flat side at a time on the head of the bolt, if you understand what I mean.
Have you ever been to a store and saw an item with a cardboard tag tied to it with a piece of wire? That's referred to as tag wire. Find some.
In the meantime. The low speed jet (toward the top of the carb on the clutch side) needs to be about 1-1/4 turn out to start. You can take it all the way out and see that the passages inside are clear. Don't lose the spring.
I find a source of compressed air and a blow tip attachment are as important as a screwdriver and a wrench when it comes to these carbs.
BTW. it's a KEIHIN carb. :biggrin:[/b]
Ok I know that every passage in that carb is clear so tommorow I'm going to adjust the fuel level. What is the tag wire for? would mechanics wire work for whatever it does?
 

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Discussion Starter · #7 ·
Ok I know that every passage in that carb is clear so tommorow I'm going to adjust the fuel level. What is the tag wire for? would mechanics wire work for whatever it does?[/b]
I've got more problems. I can't seem to get the level in the vent pipe to come down far enough. right now the motor is very flooded. I have the spark plug out and the exaust off. I also have the fuel shut off for now while I am trying to clear it. Any advice on what else to do? Is there a chance that the lever that controls the needle (yamaha calls it a float arm), needs to be bent??
 

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At this point I think you'll need to take the carb off. :console: It sounds like your inlet needle is not seating. Don't bend that needle arm. :bottom: The bolt in the bottom is for that. The tag wire is to clear your low speed and mid range jets. They're under that "T" plate, and you didn't mention seeing them. The passages below them are angled so you can't check them with a light to see if they are clear. With the carb disassembled you can use compressed air DOWN through the jets. If you don't have air, you can use (you guessed it) tag wire. The passages in the jets are small and this wire is about all you'll find that's sturdy enough to do the job. Electrial copper wire is too soft and if you break it off inside there you'll be looking for a new carb. Good luck finding one. After you clear these your machine should idle again.

This carb is something that looks very complex, but is really quite simple.

Is your oil pump operated with a cable or linkage?
 

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P.S. once you get it running right, you're gonna love the INSTANT throttle response from that butterfly carb, and you'll get some idea what it was like to ride those Yamahas of yore. :beer_cheers: That ET250 can suprise a lot of bigger cc machines! It ain't no Bravo!! :boogieboy:
 

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Discussion Starter · #10 ·
P.S. once you get it running right, you're gonna love the INSTANT throttle response from that butterfly carb, and you'll get some idea what it was like to ride those Yamahas of yore. :beer_cheers: That ET250 can suprise a lot of bigger cc machines! It ain't no Bravo!! :boogieboy:[/b]
I use to own this et250 and I sold it to a friend for his kids. His kids weren't that interested so I bought it back for my nephew but I bought it back not running. So I remember how quick it is. What I couldn't believe, the first time I experienced it, was it's low end power. My brother and his wife were cross county skiing and they were coming up a steep hill. (45degree hill more or less). Any way I was joking around and gave them a rope to hold. This is in the middle of the hill from a dead stop. The little machine acted like it didn't even now they were there. My brother and I just stared at each other in disbelief. Then he said it is because it is a single cylender. The only time my friends could pull away from me was on a lake. They also handle really well. Good for kids because the steering is responsive you don't have to plan to far ahead.
 

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Discussion Starter · #11 ·
At this point I think you'll need to take the carb off. :console: It sounds like your inlet needle is not seating. Don't bend that needle arm. :bottom: The bolt in the bottom is for that. The tag wire is to clear your low speed and mid range jets. They're under that "T" plate, and you didn't mention seeing them. The passages below them are angled so you can't check them with a light to see if they are clear. With the carb disassembled you can use compressed air DOWN through the jets. If you don't have air, you can use (you guessed it) tag wire. The passages in the jets are small and this wire is about all you'll find that's sturdy enough to do the job. Electrial copper wire is too soft and if you break it off inside there you'll be looking for a new carb. Good luck finding one. After you clear these your machine should idle again.

This carb is something that looks very complex, but is really quite simple.

Is your oil pump operated with a cable or linkage?[/b]
I don't mind taking the carb off I've had it off 5 times I am getting quite efficient at it. I know for sure that every passage is clean and clear. I used compressed air and I a small light to look threw them all. I am now conserned about what I might have done to the new gaskets because I had the lines switched and I was forcing fuel, with a primer bulb, into the wrong side of the diapham. :russian_roulette: That might be why I am having trouble balancing the fuel pump. I'm hoping that when I take it apart this time, dry out the carb kit and put it back together. It will finally work properly. What do you think ? Is there still hope? I reallize that it is quite simple. When I had it apart and it was all clean I studied it and figured out how it worked. It is actually pretty cool how it works. Oh ya my oil pump has linkage. It is a little bent rod that is fastened to a lever on a pin that is on the side of the carb which is controled by another little tiny rod that is fastened to the " clutch side" of the throttle shaft.
 

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I think if you dry everything out with compressed air you should be fine. One you get the inlet needle issue out of the way you should be able to control your fuel level good enough. I find it needs to be pretty far down the pipe to keep it from flooding. If you pipe is very cloudy and haer to see through they're still available from Yamaha, but you won't get the little red gaskets. I bought one last yer for about $12.00. You mentioned the arm bending. It should be pretty weel straight across. I wonder if you thought someone had bent it.As for the oil pump, I just remove the linkage from the carb rather than F*** with those nuts. The oil pump adjustment for my old 340 is right before the embossed line on the oil pump at WOT. Thet's the part of the linkage down throught the pump arm.

All the best...
BG
 

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Discussion Starter · #13 ·
I think if you dry everything out with compressed air you should be fine. One you get the inlet needle issue out of the way you should be able to control your fuel level good enough. I find it needs to be pretty far down the pipe to keep it from flooding. If you pipe is very cloudy and haer to see through they're still available from Yamaha, but you won't get the little red gaskets. I bought one last yer for about $12.00. You mentioned the arm bending. It should be pretty weel straight across. I wonder if you thought someone had bent it.As for the oil pump, I just remove the linkage from the carb rather than F*** with those nuts. The oil pump adjustment for my old 340 is right before the embossed line on the oil pump at WOT. Thet's the part of the linkage down throught the pump arm.

All the best...
BG[/b]
The little pipe on the side of the carb is pretty clear, I don't think anyone has bent the float arm I just couldn't think of any other way to get that fuel level down because I ran out of thead on the fuel adjustment bolt before the fuel even got down to the little indicators. That was before your suggestion to check the needle and the enrichment valve. Tommorow I am going to take the carb off, try to drain the gas out of the engine and muffler. Then I am going to take the carb apart, dry and inspect all those new gaskets and such, test the needle by seeing if gas will go by it when it is resting in it's seat, then I will inspect the enrichment valve and make sure that it is sealing properly when it is off. I will also check all the jets, passages, and ports in the whole carb again. I will make sure that the float arm is straight. I will then put it all back together, put it back on the snowmobile. Have the air mixture screw already set at 1 1/8 turn out from seated. I will then turn on the fuel. Now at this point should I prime it with the primer bulb untill I see fuel in the gas line going to the carb???? OR do I just open the enrichment valve and pull on it untill it starts??? In the many years I had this machine, before I sold it, it always needed fuel put in the cylinder to make it start the first time of the season. After that it would start 3rd pull cold and about 1/2 a pull warm. I'm asking this because I don't want to flood it again. Once I get the gas to the carb the way you tell me to I will then try to adjust that fuel level with the bolt on the bottom. At this point it should run like a dream. (OR am I dreaming) The reason I put this all into words is so that if you don't mine reading this novel you will know exactly what I am going to do. If you see anything wrong with my instuctions to myself will you let me know Please. Yes I just remove the linkage for the oil pump, that way it's easier and it stays at the proper adjustment. Those little tiny lock nuts didn't look too cooperative even if I did want to remove them. Someone mentioned to me that it could be the base seals causing all my problems What do you think about that theory?? I appreciate the time you have spent on my project I would be totally lost without your advice THANK YOU THANK YOU THANK YOU :bowdown:
 

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Here's what I'd do...

Prop up the track...
Get a brand new never fired before plug...
Disconnect the fuel line...
Take out the old plug...
You can drain the muffler if you feel you must...
Put a blowtorch flame over the plug hole...
Open the throttle wide and pull it over to empty the crankcase...
Put in the new plug...
Primer till the carb gets fuel...
Put a tiny drop of primer in the cylinder...
It should start.

Settings: key on, kill switch off, choke off, throttle closed, low speed needle 1-1/4 turns, and fuel level bolt with about 1/4" between the nut and head of the bolt.

It might even idle right off the bat.
 
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