I have a 95’ Polaris Sportsman 400. The damn thing keeps flooding the engine!!! I have rebuilt the carb and I’m still having problems… I can get the engine started, but eventually it just bogs down and dies (and I can use it as a mosquito repellent from the smoke). If I hold the throttle at a 1/3 open, it will run longer. It won’t run at WOT. When I pull the plug, I can just shake the fuel off the plug. When I pull the carb, I can see fuel lying in the manifold grommet (I can also open the crankcase drain-plug and Fuel will ooze from drain). I have a Clymer manual, but they are what they are – a cheap manual. I bought the Polaris second hand, but it has run well for many years. The worst thing this 4-wheeler has seen is it gets parked for periods of time. I do get it out and run it around the house when I can.

Here is what I have done so far:

• Compression check: 110 psi/7.5 bar. I don’t know what the stock compression should be as it is not listed in the stupid manual, but I would think this is a serviceable compression level.
• Ignition: I bought a new spark plug and spark plug cap. I clamped the plug to the frame and ran the starter for one minute – I have solid spark. It never missed a beat. I haven’t run through any of the diagnostics for ignition because I didn’t think this was an issue, besides I would have to pull the starter cover to do anything worth while. Are all of these things so hard to work on? My Fiat Spider was easier to work on than this goofy thing – I thought Polaris was one of the premier 4-wheelers?
• Carburetor: I have completely tore down the unit and rebuilt it. According to the “manual” every thing is stock. All of the Jets, needles, and valves match the Clymer’s specifications – The needle is at stock height, the bores for all jets meet the charts. The carb slide has marks, but from my experience the lawnmower looks worse (Hell, my wife’s GMC Jimmy gums up its throttle body worse than this and still runs). I suspected the choke plungerI have replaced the “Fuel inlet valve” as well as the float arm. I don’t have any specs on float arm adjustment, but the arm is currently set at .86” measuring from the carb body gasket surface (gasket removed) to the bottom of the arm. I haven’t pulled the floats from the bowl, but they move freely. When I washed the bowl the floats bobbed in the water with no hesitation (they didn’t stick) and, with the bowl dry and clean, I can’t hear any fluid in them when I shake them.
• Reeds: I pulled the manifold and checked the reeds – It is a Ten year old Moto. They had some stress marks so I replaced them with stock units. New gasket on the manifold.
• Oil injection: This was in pretty bad shape, very rusty looking. I pulled it along with all of the housing and made a block off plate out of ply wood. I surfaced the plywood with aluminum tape and sealed the crank case. This is just a temporary solution until I can find out what is wrong. I pulled the oil line to the intake manifold and sealed it with an appropriate screw/washer. I’m currently running the engine on a 40:1 mix.
• Modifications: The only modification is a K&N air filter to replace the stock air filter. I have used these for years with no problem and I had it on this 4-wheeler for several years.

Here are some thins that don’t make sense to me: If I hade a leak anywhere in the system, I would think it would run leaner. Am I totally off the mark here? I even took the old float arm and bent it to lean out the mixture and I pulled the air cleaner off entirely. All I got was worse performance and backfires. Still the plug was wet. What the heck am I missing?

 

I had the same situation with my YZ, It was the needle and seat were worn and not shutting off. Might want to replace them.

 

Sounds like the float isnt set right or the needle valve and seat are bad.

 

Yeah...the Polaris 2 strokes engines shake from front to rear and are notorious for wearing out the the needles and brass seats. definately raplace them and you should be o.k.!
Good Luck!!

 

If it is smoking as much as you say I do not see how it can be related to the carb. I would suspect you oil pump is stuck in a position that is allowing more oil in than what is required. How the dealer adjust the pump and then cover it wil silicone as this used to be a problem area on this machine.

 

Good point Snowwolfe. But he put an oil pump block off plate on, so he is not running the pump. I would tend to agree with the others about the float, adjustment or needle. However, in reguards to Snowwolfe, you didn't mix the gas/oil too rich did you?
BryceGTX

 

Whuggs1: When you say "needle", are you refering to the needle attached to the slide or are you talking about the Fuel inlet valve? I have already replaced the fuel inlet vavle (in the float bowl).

ftwflh: Does anyone know what the hieght should be? I replaced the arm along with the Fuel inlet valve. The orignal arm had wear marks. Also, in some of my preliminary testing - I bent the original arm and leaned it out. Still had flooding on the low end and backfires on the top end. This thing isn't even drivable at this stage.

400EXtremeguy: - I concur!! I had to prop my gas can on a ladder next to the 4w just so it wouldn't shake off!!

BryceGTX: I didn't have anything to go on - so I mixed 40:1 (better to be rich than lean). What should the pre-mix be?

To All: Also, I neglected to mention that I did replace the choke plunger too. As a matter of fact I even adjusted the cable to jam the thing closed, just in case that was the problem. Do you think I could drop the needle to see if it runs better. I never thought about replacing it - good point on the vibration though. It will take another week to get parts - I'm really disappointed with the bike shop out here. Very poor service - I've been ordering parts from Ronnie's now.

Thanks for the clues dudes. I really appreciate it!!![img]i/expressions/face-icon-small-happy.gif[/img]

 

Yes the needle and seat that lets the fuel in. If you replaced it make sure that it is shutting off when the floats make contact.

 

All that smoke has to be coming from excess oil. A friend of mine had a similar problem on a 400L years ago. He could only get 12 miles on a set of plugs before it would stutter and shut down. It was the oil pump. If you blocked off the pump and mixed it at the correct ratio I have no clue. Did you double check your calculations? 4 gallons of fuel would only need 12-13 ounces of oil.

 

Snowwolfe: So 40:1 is a correct ratio? I'm thinking it's only smoking beacuse it is so rich right now. I'm telling you I can litterally shake the fule off of the plug, it is that wet. I opened the crank case plug (Not the counter balancer plug) and let it drip dry over night. I probably drained off about 1/2 ounce out of there.


Speaking of drain plugs, There are three: Crank Case, Counter Balancer, And Recoil starter. Being that this thing is a 2-stroke, I'm not real sure I understand what the crank case plug is used for except in my case of draining off excess fuel. What I'm really confused about is the Recoil drain. The (all but worthless) Clymer manual says dump 70cc of oil in the counter balancer, but doesn't say anything about the recoil starter.