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Discussion Starter · #1 ·
92 440 sport fan cooled. Cleaned the carbs, now it starts hard, but it runs fine when driving, but when you stop the sled dies right away. You might get it it to stay running if you get on the throttle right away and hit the choke. Usually it will die and you will need to choke it with the throttle held wide open start again. What should I be looking for? Did I mess up some adjustments? I thought I got it all clean and put back together correctly. Any help would be great. I don't want to start just messing with settings without having a clue what I am doing.

thanks,
peter
 

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Did you mess with the idle adjustment screws? How did you clean them? Do you have free play at the throttle lever at idle? Hows the pilot jets look. Here is a fairly good link for doing it Disassembly and Cleaning of a Mikuni Round slide Carburetor Except I would not use wire for cleaning jets. I like to soak mine for at least a day and or replace the jets.

Then you need to sync the carbs. Synchronize the slides at WOT so all the slides are exactly the same position at the top of horizontal bores of the carbs. Adjust the throttle cable to get this done, if your throttle cable is cracked where it enters the top of the carbs, get a new throttle cable or it will be impossible to have 100% synchronization throughout all throttle positions.
Now that all slides are synchronized, meaning all two are being pulled equally by the throttle cable and all are in exactly the same location in the carbs, Now adjust the two idle screws so the slides touch them at exactly the same time when letting off the throttle. Now the slides are synchronized at idle position. If idle rpm is too high or too low, turn each screw by exactly the same amount until you reach your desired idle rpm. Press the throttle to lift the slides off the screws while turning them.
 

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Discussion Starter · #3 ·
Ok, followed the instructions above. I also took the air box off to see if I could see anything when it was running. I noticed that on one carb it was blowing gas out of the carb. A very fine mist but it was blowing it out.the other carb was fine. Any Ida's on where I go from here?
 

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Some mist should be present. Being you said in your original post that you have to hit the choke to get it to go off of idle tells me you are not getting fuel through the one carb at idle.
Clogged idle jet - the orafice is small in this jet and it is the first to get clogged with tiny varnish particles and/or dirt.
Symptoms- poor idle or no idle, you may need to feather the choke to keep the engine running at idle Did you clean or replace that pilot jet [idle circuit] real good? you may have a needle and seat or float not functioning properly Make sure the floats move up and down real easy and I would just change the needle and seats with the viton tip one
 

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Discussion Starter · #5 ·
I took out and ran a wire through the bigger main jet that the needle goes into, I also removed the small jet that you have to use a long small screwdriver to get to that has two sets of horizontal holes in it as well as a hole running through the jet vertically. I could not get the wire to go through vertically but could see light through it. I could get the wire through the horizontal holes. I have the air adjustment set to 1.5 turns out on both carbs. I also took the float arm and valve assembly for the fuel inlet off and cleaned those. I did not remove the floats due to there being a round plastic cap on top of the float guides and they did seem to move freely.

So when I get the sled started it is real boggy and will not stay running while at idle ( I had it in the garage with the air box off so I had better light and more time to look at it). I have to keep hitting the gas to keep it running and eventually that does not work and it dies. Sometimes with a combo of choke and gas I can keep it running. I then can restart after a few pulls and choking it again and holding the throttle wide open . I also noticed at this time the fog of gas that comes out of the one carb. This sled has always been such a bullet proof runner for me. Now this fall it is being a pain in the butt.
 

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This is what forums are all about, helping people. You come on here without an attitude and you will always get help. Seeing as how it appears you've gone thru the basics for the carbs, you should consider going thru you're entire fuel system starting from the pick up inside the tank and follow all the way back up to the carbs. I have experienced what your describing a few times, ended up being a clogged pick up inside the tank. Check all your fuel lines, clamps, change the filter etc..also if the fuel in the tank is suspect, remove the tank, fully drain it and make sure its clean in there. Top off with fresh premium fuel and see where that takes you. As far as the carbs go, if you're not 100% sure that they are cleaned and setup right, its best to take them to someone with the correct tools and experience to clean them and set them up.
 

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Discussion Starter · #8 ·
I put fresh premium gas in already and every time I take off the carb and turn it upside down, I get gas pouring out of the small vent on the top of the carb. So it appears to be getting fuel. However I will inspect the lines going back. I am getting close to taking it into a dealer and taking my lumps but I have kind of always prided myself on fixing these sleds. I did not pay a lot of money for them so it is hard to justify spending lots on them but I hate to see a perfectly good sled sit and not get used. I have read something about the piston skirts breaking, that sounds serious could that be it? Also wondering if the chokes could be sticking or something simple like that. I am not sure what to look for on those items.
 

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I wish I was there to help you. What do the plugs look like when it does run above idle? You may be sucking in air with cracked carb boots and or crank seals. Your fuel pump may have a hole in the diaphragm. You say it runs fine above idle? No bogging or popping ? And check everything out that Canadian XCR says. Dont give up you will get it
 

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Discussion Starter · #10 ·
Yes it runs fine when you are moving along. Just when you stop it wants to die. You can then squeeze the throttle and it will bog down and then come out of it and go, or die. Then pull and pull and it will start but it will only start by choking and giving it throttle. Boots look fine, but I will look at them more closely tomorrow. I will also check the plugs. The fuel mist coming out of the one carb just does not seem right to me. I had a motorcycle that had valves that had tuliped and was shooting gas out the carbs on the power stroke. I know sleds are different but that is what made me go hmmmm when I saw it. Should the float bowls be empty if it was a gas pump issue? Also how do I check the fuel pump? I can replace the fuel filter but I have never delt with a snowmobile fuel pump.
 

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I put fresh premium gas in already and every time I take off the carb and turn it upside down, I get gas pouring out of the small vent on the top of the carb. So it appears to be getting fuel. However I will inspect the lines going back. I am getting close to taking it into a dealer and taking my lumps but I have kind of always prided myself on fixing these sleds. I did not pay a lot of money for them so it is hard to justify spending lots on them but I hate to see a perfectly good sled sit and not get used. I have read something about the piston skirts breaking, that sounds serious could that be it? Also wondering if the chokes could be sticking or something simple like that. I am not sure what to look for on those items.
The symptoms you described are not likely a choke problem. Check them though, because its quick and easy. IIRC its a 12 or 13mm nut where the cables run into the carb bodies. They should simply unscrew and pull out. Clean the ports as its likely you'll find gunk in there. Wipe off the plungers, they should wipe clean easily with no gunk on them.
 

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Yes it runs fine when you are moving along. Just when you stop it wants to die. You can then squeeze the throttle and it will bog down and then come out of it and go, or die. Then pull and pull and it will start but it will only start by choking and giving it throttle. Boots look fine, but I will look at them more closely tomorrow. I will also check the plugs. The fuel mist coming out of the one carb just does not seem right to me. I had a motorcycle that had valves that had tuliped and was shooting gas out the carbs on the power stroke. I know sleds are different but that is what made me go hmmmm when I saw it. Should the float bowls be empty if it was a gas pump issue? Also how do I check the fuel pump? I can replace the fuel filter but I have never delt with a snowmobile fuel pump.
Time for a compression test. Should be at least 110psi each side, ideal is 120ish for that motor. Both sides should be close. If that passes, time to check for air leaks, after you've gone thru the fuel system as described.

About the fuel mist out of one carb, usually not a big deal. Proper tuning will get rid of that...there will always be a tick of it though, nature of the beast..
 

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Discussion Starter · #14 ·
Well here is the latest of my testing and work on the troubled 440. I did a compression test and I was at 120 on both cylinders. Next took the fuel pump off (could that be in a tighter place or what!). I really did not know what to look for but when I opened it up, everything looked in tiptop shape. No cracks or anything that would look suspect. I put a new fuel filter on. I then checked carb boots. No cracks and in good shape. So I put it back together and thought I would give it a try. It would fire with full choke and I would have to go wide open throttle to get it to kind bog and start. I had it on a stand and then I finally got it started and got it out of the boggy start an got it going wide open. The engine make a bit of a stutter and then it ran much better. Almost like something broke loose. I could then let it idle and it would idle fine. Now the issue is it is boggy on the start and it still blows a lot of gas out of the one cylinder when you give it the gas and it bogs. I could then shut it off and restart without issue. However it bogs and dies if I hold it WOT from a start. I can feather it and it will go just fine. So now, what do I want to do? Progress, but now what?

Thanks,
Peter
 

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Sounds to me as if you still have carb problems. You could switch carbs and see if the one blowing gas transfers itself to the other side. It probably will. Here is a link to mikuni throttle opening showing you what circuit is involved. Tuning Tips & Manual Downloads

It really sounds like your pilot circuit is still plugged. I have had a needle and seat not sealing properly and had gas spewing out all over but this will cause a flooding issue.

Also I was reading your first post. Did the machine run good before you cleaned the carbs?
 

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Discussion Starter · #16 ·
The sled ran like a top last year. My wife is giving me the business about how I must of wrecked something! I wanted to clean the carbs due to when I took the top of the carb off there was yellow varnish all over the slide. I thought that was not good so I proceeded to clean things up. That's when I had the trouble.

I will swap the carbs around and report back as well as take a look at cleaning the offender again. Thanks again to everyone that is helping me out!

peter
 

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Sounds to me as if you still have carb problems. You could switch carbs and see if the one blowing gas transfers itself to the other side. It probably will. Here is a link to mikuni throttle opening showing you what circuit is involved. Tuning Tips & Manual Downloads

It really sounds like your pilot circuit is still plugged. I have had a needle and seat not sealing properly and had gas spewing out all over but this will cause a flooding issue.

Also I was reading your first post. Did the machine run good before you cleaned the carbs?
I agree. It could even be a problem with pilot air system. You might not be getting enough air at idle which would lead to too much fuel. I feel your pain though, I just cleaned my carbs last week and got the wrong needle valves - gas was blowing out of the carbs like you wouldn't believe because the needles wouldn't close and I ended up filling the whole engine with gas. I put the old ones back in and it ran like it was new. I'm not sure how you clean your carbs but what works best for me is taking everything completely appart, letting everything soak in parts cleaner for 24 hours, spray everything down with carb cleaner and in every hole, then blow everything out with the air compressor. It doesn't take much to plug some of those holes.

It sounds like you've done your due diligence on fuel system up to the carbs. If it were me I would probably rip into the carbs again.

Good luck!!!
 

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Does your machine have a fuel petcock (shutoff)? If so, try this. Get the machine running as best you can, and while its running turn the petcock off. Let it run for 10-15 seconds or as long as you can. Leave the machine with the fuel off overnight. See how it starts the next day, if it starts easier then you may have a leaking needle & seat. I have seen them go bad with low mileage. I had to replace mine on my XCR after only around 1000 miles because it became hard to start and keep running after sitting with the petcock on.
 

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Those carbs are dirty, clogged, or adjusted wrong. Sadly, one of the best ways to get them clogged up is to clean them. Often, you dislodge something and it blocks the passageway somewhere else.

Get yourself some SeaFoam Deep Creep, pull the carbs, break them ALL the way down, spray ALL of the passageways with the Deep Creep and let it sit. Then run fine gauge wire through all of the openings in the carb bodies multiple times as this should break up any small clogs and allow them to make their way out.

Clean everything off with spray carb cleaner, then a LOT of compressed air through all of the passages.

Set your air screws to 1 turn out to start, make sure that the slides move in perfect sync, and be sure to properly set the idle when you first put it together. Once it's warmed up, adjust the air screws until the idle speed increases (1/8 turn at a time, both together). Reset the idle and repeat until the idle doesn't change. Reverse the air screws 1/8 turn and call it good.

Dump about 4-6 ounces of SeaFoam (not the Deep Creep stuff) into a full tank of fresh gas (don't waste your money on premium - it's more stale than regular). Do this for a few tanks of gas. As you notice the idle creeping up, reset it.
 
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