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I remeber seeing an article on here about K&N pods but can't find it must have been lost in the move.  I am considering putting K&N pods with snowgaurds on my 00 zr500 carb.  My reasons are of course more power and also i'm sick of playing with the stock airbox.  Its a pain to get in and out and bairly fits being i have reed block spacers.  Are K&Ns worth it should I consider another brand, what size do you suggest, and do i need a filter with angle to get over the jackshaft?  Thanks for any help in advance.
 

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The small-block cat motors do not get allot of gains from the spacers, and if it was mine, I would remove them if they make removing the airbox that bad. Reed spacers increase crankcase volume which lowers filling compression which makes it harder to fill the combustions chamber.

Look at the fresh air intake kit from SLP. A friend has one on his 2001 ZR800 and I am actually quite impressed with how it works and looks.
 

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Discussion Starter #4
I never been a real fan of the airbox.  It didn't fit real well before i added vforce and reedblock spacers.
 

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It has been proven that an airbox with carb venting will provide more consistant and acurite jetting. If you are lake racing, then filters are good. You could consider a whole airbox replacement from SLP. Friend has one on his 99 ZR500. Just with pods, be prepared worry about water/snow injestion. Even the pr filters will absorb water and prevet airflow.
 

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ARCHIVED ARTICLE COPY!

We've received quite a few feature request surveys for a product evaluation of K&N's snowmobile carburetor filters. While we have heard countless horror stories of sledders gutting or removing their sled airboxes, we decided to take a closer look at the pros and cons of installing alternative air filtration.


Air Intake Basics:

There is a lot of confusion when it comes to sled air intakes. Many sledders falsely believe that ALL sleds filter the incoming air before it enters the carb. This is not necessarily the case. While some sled models do provide air intake filtration, many others have none at all. Grass racers in particular will tell you that aftermarket filtration is crucial for performance and to prevent carb/engine damage.

Our interest in carb filters came when we began racing & testing on grass. After making several runs, we noticed that a small amount of dirt was accumulating on the intake side of the carb. We reasoned that if dirt was making it to this point, it was also entering the engine.

To prevent carb slide and engine damage, we decided it was time to install some aftermarket filters. We installed a set of the cheaper foam pod filters and have been running them ever since.


The Difference of K&N:

It wasn't until the feature survey that we had the pleasure of trying something different. Our only wish is that we knew how well they worked sooner.

Our K&N filters that we received were sized for a 38mm carb. We elected to use the 6" long model for maximum air flow. Our filters were packaged professionally and came sealed in an air tight plastic bag.

K&N filters are cleanable, and can be reused over and over again. After cleaning you must pre-charge the filter by spraying them with a special oil. Our filters came ready to use since new filters already have this oil added.

Installation:

We began installing our filters on one of our stock sleds by first removing the airbox. This can become somewhat difficult depending on how much room you have to work with. After removing the components mounted on the top, we pulled and twisted the airbox until it became free of the engine area. It's amazing how much room an airbox takes up. A benefit that you will see clearly after installing these filters is the addition of much more room, making jetting and maintenance a breeze.

We patiently relocated each component that was previously mounted to the airbox. This included a fuel shutoff valve, two ignition coils, and a CDI box. Take your time with this process so that you end up with properly routed hoses and wires to make the installation look professional.

In preparation for filter installation, we removed each carb and disassembled. We thoroughly cleaned each carb (preventative maintenance) and removed the main jets. NOTE: AIRBOX REMOVAL CAN LEAD TO SIGNIFICANTLY DIFFERENT JETTING REQUIREMENTS. ALWAYS INCREASE JETTING ADEQUATELY TO DETERMINE WHAT NEW FUEL LEVEL YOUR ENGINE MAY REQUIRE.

Since we were already jetted as low as we could safely go on our sled, we bumped up the main jets by five sizes. This resulted in jetting well above the stock levels. Depending on how restrictive your stock airbox was will determine how high your jetting will need to be. Always start off with high jetting. You can then determine how lean or rich you are running and begin to come back down a little at a time.

We reassembled the carbs and installed them back into the engine boot. We slipped on the K&N filters and tightened each one. Their fit was excellent and actually dressed up the look of the engine area.

Testing:

There is one important aspect that we would like to make perfectly clear to everyone: You must be very careful when making changes to the fuel/air ratio of your engine. Now that everything is back together, DON'T take your sled out and run it wide open to feel the difference. We first must determine whether the engine can safely operate at this new jetting level.

Start off with making a 1/4 throttle run and kill the engine while at that throttle position. Compare your plug color AND piston wash to see if the jetting is safe at this throttle position. We had EGT gauges (see Digatron article) installed on this sled that we know match the plug color and piston wash of our machine, and highly recommend their use for this testing procedure. Our jetting levels proved to be safe, yours may not.

If your jetting is safe then you can move on to a 1/2 throttle run. Then make a 3/4 and full throttle run using the above steps each time. If at any time your temps climb to unsafe levels, you need to adjust that area of your jetting.

Our testing indicated that we were way over jetted on the mains. We began to SLOWLY lower main jetting one step at a time while making test runs following the steps outlined above. We arrived at the correct jetting which in our case happened to be 2 sizes larger than our previous "good" setup (before filters were installed). With our jetting correct, we decided to make some trial runs.

We did notice a slight increase in air intake noise, but nothing too major. The filters do tend to change the sound of your engine a little bit.

After running, we did note an improvement in mid range and top end. While this was not a huge performance difference, we definitely could feel it pulling better, not unlike the feeling you get when riding on very cold days. Most serious tuners will admit that K&N filters can make a big difference, depending on your stock airbox restriction level. Our engine was breathing better which in turn provided better performance.

Conclusion:

With a bit more performance, along with the ease now of carb adjustments, we feel that the K&N filters are definitely an upgrade from stock. Even normal maintenance is easier with the increase in room that we now have since the airbox is gone. Our filters excelled in keeping dirt, snow, and ice from entering our carbs and ultimately our engine.

If you do plan on running your sled in extreme conditions though, K&N offers serveral options for even more protection. The "Precharger" should be used when running your sled in HIGH dirt conditions such as at a grass drag. The "Snowcharger" reduces snow dust entry into the carb, reducing plug fouling and carb freeze-up.

When comparing the K&N's with our other sled's foam pod filters, we found another benefit. The K&N filters provided significantly better filtration with less air restriction. Our jetting levels decreased with the use of the cheaper foam pods, yet more foreign material found its way into the carbs. Lower jetting sizes mean we are receiving less air supply to the engine. You get what you pay for; and the pod filters are a far cry from the technology used in manufacturing the K&N's.

If you want better performance, easier carb adjustments, and the security of high tech air intake filtration, you should consider trying a set of K&N filters.
 

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Discussion Starter #7
Thanks that was the article I was thinking of.
 
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