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Thread: air box problem on my Widetrak LX. Need advice

  1. #1
    Member mainer_in_ak's Avatar
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    Default air box problem on my Widetrak LX. Need advice

    All the foam pieces of my airbox on my Widetrak LX keeps getting plugged with ice crystals and snow when I run in really deep powder, or when snow falls on the machine. A few days ago I tried to start my machine and it wouldn't idle for crap (that's how I found out). Upon pulling the plugs, they were wet and black with carbon. Apparently, all these darned pieces of foam were too plugged up with moisture and ice crystals that it made the engine run extremely rich and cold. Once I cleaned the plugs and pulled all that foam BS off the top of the airbox, the problem has seized to exist BUT the motor is now exposed to taking in snow.

    I'm tired of these air box problems and was considering a couple universal K&N air filters that are large enough to be clamped to each carburetor. I took out a set of calipers and measured the outside diameter of the carbs and was thinking of simply purchasing a couple universal K&N filters. Would this be OK?

    I don't like messing with such a reliable stock motor like this 500 liquid BUT I think this airbox crap needs to go. Any suggestions? Because of this airbox issue, fuel mileage has been effected too, that was the second sign that something was wrong.

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    Member AKDoug's Avatar
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    If you go to K&N's or sock filters on the carbs it will most likely not run right. Drawing warm underhood air or moist underhood air really screws with your jetting. I've made a couple work in the past, but my experience is that an airbox is the best way to go.

    For my two sleds that have filter issues I use SLP pre-filter fabric.http://www.slp.cc/catalog.cfm?pageID...&productID=367 Remove all the foam and replace with this fabric.

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    Go Pro (on Potter in Anch) stocks SLP filter fabric. You can get pre-cut kits, too.

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    K&N or UNI-FILTERS work great you usually have to adjust/rejet but easy to do. On almost every sled I have ran you can keep the pilot"IDLE" jet stock, on the Needle in the slide just raise the needle/lower the Eclip one position. And on the Main jet usually go up 2-4 jet sizes like from a 260 to a 280 is usually all thats needed, this is caused by the increase in air flow to the engine causing the engine to run lean as factory tuned, the pilot/idle jet has plenty of adjustment for your set up the mid range really is good with a minor increase in fuel hence the 1 position lower on the Eclip, on the main jet you need the most fuel, Main jets are cheap and easy to swap get a few bigger sizes and go to work.
    Put new plugs in and start the sled get it idleing nice and smooth let it idle for around 1-2 min hit the kill switch pull the plugs and read them-light brown is great if its a bit white richin it up if dark lean it out. For the mid range lift the rear of the sled up to clear the track start the sled and run it at half throttle no more than half throttle run for 30-90sec and hit the kill switch with the engine running at half throttle so as to not let your idle settings taint your plug read. Pull plugs and check raise E clip to Lean, Drop to richen you want a nice chocolate brown now.
    Now the fun go out to a stretch and run you sled wide open for 30 seconds max same routine Kill the sled with an absolute min of time below full throttle, pull and read plugs, if they look good repeat the run for 45-60 sec pull plugs and read if they are good you should be good to go unless you are racing that beast if so repeat the runs up till 2 min WOT to ensure you wont go dead lean and melt some pistons.
    I know it sounds like a lot of work but its and hour or two max to get it running great. You will have a great running snow free sled and will enjoy a few more HP and some extra MPG as well. Have fun PM if you need any help
    RLTW
    HUNT HARD HUNT SAFE
    WILL

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    Default under hood temps?

    Most of your problem is the under hood temps and snow ingestion. When the snow is this deep, it tends to fill in under the hood and melt on the exhaust / motor. Cooling down the intake and forming ice, not good for the motor at all. The ice will make the motor run rich and lack of power. You need to install a bib kit to help keep the snow out and the temp up. Polaris use to make this kit, now they have to be made. If you want to try this idea first, duct tape and some card board works well. Block off the vents and take it for a spin, keep in mind that this is for cold weather and deep snow only. You can make the temp under the hood to hot and start having clutching / running problems as-well. You have to adjust to the conditions of the snow and temps.

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    Member broncoformudv's Avatar
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    Like everyone else has mentioned you need to filter that snow out and the best ways to do that are with the SLP screen or some other sort of screen material. Pet proof screen is pretty popular with a lot of people and is fairly cheap to buy at the pet stores.

    Put the screen over all your vents on the cowling and over your air intake and you will be good to go.

    Take a look on www.backcountryrebels.com or www.snowwest.com lots of good ideas on both of them for home made filters and vent screening.

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    Member mainer_in_ak's Avatar
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    Well, I purchased a couple K&N air filters directly from the website, in combination with the little covers that prevent snow from plugging up the filter pleats. I'll keep the stock air box in case the K&N's become too troublesome. In not crazy about changing jetting, is this a definite?

    Heck, I'm not crazy about doing any modifications to a reliable work machine, but this stock air box is already cracked any way. If it wasn't cracked and repaired about twice already, I would have gone with that material mentioned by Doug and Pid.

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    Member AKDoug's Avatar
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    Jetting will most likely be mandatory. The good thing is, the jetting will most likely need to be leaned out. That means if it gives you trouble it's going to be running rich and that won't burn a motor down. HOWEVER, with some airbox and hood designs you may have to go the other way. Both sleds I have attempted K&N's on have had to be leaned down to run right.

    Here is why I don't like pods and why I'll never run them again. When you draw air through the airbox it is pulling outside air at the outside air temperature. The temperature of the intake air is relatively constant and you can predict jetting based on this. Pods (K&N's) draw warm underhood air. Sometimes it's warm, sometimes it cold. It's constantly changing depending on a ton of variables like outside air temp, speed you are traveling, whether your hood vents are open or whether they are closed, not to mention moist steamed air getting sucked in.

    That's just the tip of the iceberg on pods. Proper air resonance is important to two strokes and the airbox is designed to provide this. It's pretty complicated to cover in a post like this, but you can easily Google it.

    You may be just fine and I doubt any experiments you do are going to harm the engine since the 500 Polaris is a pretty mellow engine. However, if it runs too good stop immediately and check plug color. Every sled I've burned down ran the best right before it seized

    Oh, and one last thing. The airbox helps support the rear of the carb. With pods this doesn't happen so you get shortened carb boot life since the carbs are free to move more. Keep an eye on those carb boots.

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    thanks for the advice folks. My machine is liquid cooled so this may provide some colder under-cowling temperatures.. My machine has a very reliable over temp light that always kicks on to warn me. I'll keep an eye on the plugs and I may even make a shroud on the exaust side if need be.

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    Member AKDoug's Avatar
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    Remember that the light is simply coolant temp. Every two-stroke I've been around that seized was a result of detonation (bad or too low octane fuel) or lean condition. Neither of which will trip the overheat light.

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    Quote Originally Posted by AKDoug View Post
    Jetting will most likely be mandatory. The good thing is, the jetting will most likely need to be leaned out.
    Are you sure about that? Better breathing usually requires richer jets.

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    I do know that right now, she's running rich so I hope the easier breathin helps. Cold/Dry air is more dense than moist/warm air so it may be the case that jetting will be effected by the K&N's. I really hope it goes well because I have no other choice. My air box has cracks and I'm tired of repairing it, only to have it fail in another way. I'll certainly keep all the vents covered with a piece of that fabric to keep fine crystals of ice or powder from getting under the cowling. If I just putt putt on trails, all would be good, but I love diving into deep snow drift-laden ungroomed trails to get to remote lakes or going up into hatcher's occasionally to do some climbing with the ole tank. Every instant I've checked this machine's plugs, she's always run too rich. ALWAYS because of that useless foam packed with snow and moisture. I did get the longest filters that would fit in replacement of the airbox which was six inches long x three diameter cone shaped snowmobile specific filters. I measured the outside diameter of my 34 mm mikunis and they were 2.325 in. diameter, and chose the proper filters based off that. I might even cut the airbox on two sides and keep what's left as a shroud. Is this a good idea?

    These darned filters and filter covers are pricey, It'll be a bummer if they don't work as they are cheaper than a new stock airbox, that's for sure.


    http://www.knfilters.com/snowmobile.htm

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    Member AKDoug's Avatar
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    Are you sure about that? Better breathing usually requires richer jets.
    Warmer under hood air required leaner jets on the sleds I worked on. I agree that better breathing should require richer jets if the air supply is outside air

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    We have 3 Indy 500's in our kid's fleet. All of them have required leaner jets from stock. They are all fat from the factory. They were perfect at -25F, but the kids don't ride that cold.

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    I removed the airbox about an hour ago. When I peaked inside, there was enough snow and ice crystals in there to build a snowman. The inside of the carbs were frosty. I warmed the motor up and gave both carbs the seafoam treatment first with a hearty dose of sea foam spray, and then with the sea foam deep creep oil. Once I burned it off, I cleaned the plugs and ran the motor hard for at least 15 minutes. Even without the airfilters installed, the plugs look fine. The temp was 20 degrees. Everything under there is so easy to get to with the air box gone. I don't think I'll miss it.

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    Member 58dranger's Avatar
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    Its simple The better it breathes from stock you got get richer. MORE AIR MEANS MORE GAS or you go DEAD LEAN and its called dead for a reason if the sled is fat from the factory you might be good leaving it as is but When I was working as a Mechanic in the Dakotas and Wyoming at roughly 3000-5000 foot every sled that we put pods on got factory jetting for sea level as a start, The dealership I worked as was both a SKIDOO and a POLARIS dealer. But Every Sled and Every Motor and Every Location is different. Tune and Pull Plugs thats the best way to do it. I have taken a Polaris Indy box and cut/modified it to fit a K&N car filter the flat type on the inside of the factory box below the foam It worked sweet.

    Good luck with the sled tuning have a great season
    RLTW
    HUNT HARD HUNT SAFE
    WILL

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    My advice would have been to find a new airbox and add a TempaFlow. It isn't too late.

    Prefiltering snow has been sucessfully done for 20 years since those Indys were new. That mission will not change with the swap to K&N filters. You have to guard against steam ingestion. Those old Mikunis like to freeze up, especially at the chokes. Get in the habit of cycling the choke lever at shut down. Jetting and re-jetting was always required on the Fuji 500 engine. It'll be even more important now.

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    Yes,
    I'm not too thrilled about these K&N filters either, but I have my fingers crossed that they will work.

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    Mainer,

    I suspect your troubles will be with under cowl temps. Most guys that use K&N filters are riding sport sleds fast. You're dealing with a work sled that will work hardest going slow. Your temp variations will exceed what the fast sport sleds see, and with a motor that's particularly sensitive to temp changes. Keep a close watch. When you work it hard you'll probably be running really rich.

  20. #20

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    The only thing I would be the lightest bit concerned about would be the Rubber Carburetor Mounts...between the engine block and the carburetor. The additional weight of the K&N Filter, being non-supported could lead to premature failure/cracking of the mounts, causing a lean condition. Seen it happen. Watch for cracks developing in the mounts.
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