Running on One Cylinder

[kwiggy]

I have a 95 Indy Sport 440 fan cooled that starts great and idles good for a little bit, but constantly needs to have the choke flipped momentarily to keep it running. It seems like it is running on one cylinder. It runs better when it is warm, but still doesn't run perfectly. Higher rpms (speed) the machine will run on two cylinders and perform just right.

Last year I replaced the ?voltage regulator? (I think that is what it is... little black thing on the side of the cylinder head) I mention this little fact because that helped my 95 Super Sport run better, but it didn't help this one.

Yes, I did change the plugs.

I have a feeling the problem is in the carbs, but I am afraid of carbs.

Any advice would be much appreciated. Thanks

[lawdog]

carbs...you already know what the problem is. start with a thorough cleaning and go from there.

[hanson]

Your problem is more than likely the carbs or carb.

Anyone know if the Sport 440 is running 2 or 1 offhand? Alot of the more entry level sleds only run 1 carb and am not sure if this is the case.

Carbs have 2 circuits in them, a low speed (or idle) circuit, and a high speed circuit. At idle, fuel flows through the pilot jet into the carb body and into the engine. When you give your sled throttle, the "jet needle" which is attached to your throttle raises in the carb allowing more fuel to flow through the main jet and thus into the engine. The more throttle you give, the higher the "jet needle" raises and the more fuel that is delivered to the engine. So at idle and low speeds, your fuel is delivered through one circuit (pilot) while at high speeds your fuel is delivered through the other circuit (main).

If either of these "jets", the pilot or the main are plugged with debris, or varnished up from bad gas, old gas, or sitting awhile, you'll have a hard time because less gas flows through the jets. And in your case, its the pilot that is causing you problems. The main is clean which is why the sled runs good at higher rpms.

Carbs are nothing to be afraid of, they are pretty simple when it comes down to it. There really isn't much "tuning" involved, its just taking parts apart and off and reassembling them the same way you took them off.

I learned on my own from a Clymer repair manual. I would pick one up for your sled and the manual will walk you through it step by step.

If you need more help or clarification, definitely feel free to ask here. I think a lot of us have been through the carb cleaning routine. It really is no big deal but that first time is definitely intimidating

[swedishpimple]

I think the 440 Sport had one carb and the Super Sport ran 2 carbs....not sure and I i don't have time to look it up..ha ha....I self taught myself on the carbs. They are very simple. Toughest thing is to get them out to work on. Taking them apart is simple....just be organized. Go to an OEM parts diagram.

http://www.partsland.com.....polaris has a link off of there site too with detailed diagrams. The pictures are great....but things look a little different in real life.

[lawdog]

If that's a single carb unit, you may have to look electrical if you are having problems on only one cylinder, but I'd still start with cleaning the carb well. An occasional cleaning is essential maintenance anyway.

[311Hemi]

Might check the coil that the plug wires connect to.

[GoggleEye]

I don't know much about sleds, but can a bad resistor cap cause this problem??? Just a suggestion, like I said I don't know much.

[kwiggy]

Thanks for the help and advice. I feel a bit more confident about carbs now. I do agree that they are hard to get out... maybe that is why I've never wanted to tackle them. Both of my sleds (sport and super sport) have dual carbs. I have thought about picking a carb up at haydaze to learn from and have as an extra.

2 more questions: What do you use to clean carbs that is safe for the rubber parts? If I can't get my settings correct upon re-installation, do you recommend taking it in to a shop... or asking you guys for some forum help?

Thanks to everybody for the help. This forum is way too cool.

[NAMASafetyDirector]

Standard parts washer fluid will work or I just typically use some carb and choke cleaner. Just make sure if you use parts washer fluid that it is cleaner that what your trying to clean. I have seen guys introduce more junk into their carbs with dirty cleaner that they originally were tryin to clean out! As far as the settings your local dealer should be able to get you the spec. for your fuel screw and idle setttings. Just make sure when you re-install that your carbs or timed correctly, meaning they start opening together and also that they come to the wide open throttle at the same position. You want both slides to fully disapear from the carb bore at W.O.T. One last thing, when you remove the carbs, take a good look at the rubber carb boots that go between the carb and the engine. As these get older they have a tendancy to weather check or crack especially when your trying to remove or intstal the carbs. If these are cracked you will have excess air getting into the engine and create a lean condition. Seen many a sled burn up pistons due to this oversight! It's always good practice to replace the fuel lines and filter at this time as well,(just a piece of mind thing). Dont forget about the impulse line that goes from the crankcase to the fuel pump, that one has stumped me a few times! If it is cracked it will cause the pump to not work correctly and one cylinder normally suffers. Might just be your problem! Good Luck

[CalderPointCabin]

yes, clean the carbs ensuring the pilot jet and main jets are clear.

your symptoms are the classic symptoms of a plugged pilot jet.