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Blown up Formula said:
hey, i put k&n filters on my 1998 583 formula dlx. do i need to change jet size due to the potentialy higher flow of air?
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K&N recomends re jetting when using any of their filters on a snowmobile.
 

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Discussion Starter · #4 ·
so what should i change to? Is it actualy going to help utalize the filters?? will i notice much change between just having the filters??
 

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I'm going to have to switch to K&N snowchargers also, the mounts on my airbox broke, so wondering the same thing, or will it still be running in the safe zone with just the K&N, and stock everything else.
 

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i heard it wasnt safe to run K&N's... i heard its risky business for the engine... is that true? what kind of advantage do u get from them?
 

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Discussion Starter · #7 ·
J_Cooke said:
i heard it wasnt safe to run K&N's... i heard its risky business for the engine... is that true? what kind of advantage do u get from them?
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actualy i would like to know this too. this is a great question, cause i put them on my 500 and ended up blowing it up. I also had a bad spark plug wire, so that might have been the cause. sometimes the plug would not fire, so when it started firing again, it would have a slight backfire, so i think that just weared at the piston and sooner or later blew her up. but i dont see why this would happen due to the filter. On any other engine, if you put a better flowing filter, it helps with performance. not saying this didnt help cause it did, but i dont think a filter could blow an engine.
 

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K&N's could potentially suck in more snow too. As for the AC pipe on the Doo....Wouldn't recommend it, even if you did manage to physically fit it in. Either way, it'll make your sled twice as heavy and slow as hell...lol.
 

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I run K&N filters for the grass drags and water x races just because they wont let the motor suck up dust like in air box will.
Cant really comment about richer or leaner since ive always jetted down for the warm weather and always ran K&N.
If you are going to run them in the winter i would defintely take a few plug readings, and they also make a prefilter to keep water out of them.
Another thing to keep in mind about using them in the winter they will be drawing in alot warmer air then a airbox will due to the engine heat.
my $.02
 

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Discussion Starter · #13 ·
i use them and noticed about 10mph in about a football feild. might not be exactly 100 yards, but i took off and looked down both times when i had the box and then when i had the k&n on there. My big question now is would putting k&n's help blow an engine?
 

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Blown up Formula said:
i use them and noticed about 10mph in about a football feild. might not be exactly 100 yards, but i took off and looked down both times when i had the box and then when i had the k&n on there. My big question now is would putting k&n's help blow an engine?
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Yes, if you didn't properly rejet after installing them. They lean the A/F ratio out so you must rejet after insatllation to make it correct, otherwise the lean condition may be enough to destroy an engine at low temps. Also, like I said I heard they fall off easy. If your sled had them on it and it was jetted on the ragged edge of lean and one fell off, then that cylinder would now be even leaner... boom.
 

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K&N flow more air, rejet 2 sizes larger too start, thats if you still have the stock jetting as the sled came from your dealer. If you are riding in conditions where there is snow dust, You MuST us the pre filters, If you want for added insurance to keep them from falling off take a piece of aluminum bend it at 90 degrees mount to bottom of tunnel near jackshaft make it tall enough to slip over the bell of the carb. intake side using a hole saw cut out an opening just large enough to slip over the bell of the carb. Mount far enough back so that the filters will slip over the bells, tighten filters and have fun. After you get your jetting correct, make sure you keep an eye on it during large temp swings. The plate will keep carbs in place during rough riding conditions and when the engine moves under torque. Even without this plate I have never had K&Ns fall off.
 

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Discussion Starter · #16 ·
mine did not fall off, and im 17 and ride some ROUGH trails, preaty fast. Im talking about 50mph down a real rough back trail. No problem with them falling off, the sled blew up on a streight away after holding her wide open for about 7 miles.
 

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If you were to list the pro's and con's, filters vs airbox, the box wins by a big margin IMO.

Start fat on both the needle and mains, at LEAST 1 clip and 2 mains. Often even after careful tuning there may be a lean spot thats hard to cover without being too rich somewhere else.
 

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Discussion Starter · #18 ·
why is the box so much better? The filters are faster for sure, yeah i konw the whole heat thing, but i would not think that heat would be a prob doing 50-60mph because of all the stock holes in the hood, i could see at low speeds how the temp would affect it for sure. but its faster.
 

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I dont see how the airbox is much different, mine is just a hollow box with 2 holes in the bottom, and a big one on the top with a foam pad that goes over it, and nothing in the middle, just a huge empty space.
 
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