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Join Date: Nov 2007
Location: Chandler, Arizona
The one and only purpose for an air filter is to clean the air before it enters the engine. Dirt in the air/fuel mixture will destroy an engine in a very short time. When a manufacturer designs an engine, they take the stock filter into account when they decide on the carburetor jetting. It all works together to protect the engine from dirt, and provide the proper air/fuel mixture. Hopefully, this is common knowledge on a motorcycle forum. When you make a filter less restrictive, the only way to do it is to make it more porus, which means more air gets through, but it also means more dirt gets through.
My dirt bike has a stock foam filter, which I wash in gasoline, and reoil after every days riding. I've had this bike (Honda XR400) for almost 5 years, and it shows no sign of engine wear. I replace the filter after so many cleanings with an aftermarket (Emgo) version of the stock filter. (much cheaper) K&N makes a filter for this bike too, but I won't use it. I want my engine protected.
I also drag race an '85 400 c.i. small block Camaro, which I built myself from the ground up. It has an Edelbrock tunnel ram intake, dual 650 CFM Holleys, topped with a Mr. Gasket street scoop, and of all things, a K&N air filter. But this is not a daily driver, it is towed to the track, and the scoop is kept covered except when actually racing.
IMO, K&N filters are only good for racing, where they see very limited use, and should never be used on street vehicles. I mean, you wouldn't put racing slicks on your street bike would you? They actually do work great on sportbikes, though they don't last very long, but hit the tiniest puddle of water, and down you go. And while I have slicks on my Camaro, there is no way you could use them on a street car. They would most likely last under 100 miles, and there is no way you can balance them for street use.
But, if you want to use K&N filters on your bike, by all means do so. It is after all your bike. Maybe it would work better with straight 60 weight racing oil too. Jerry.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike