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AFTERMARKET AIR FILTERS
Although aftermarket filters are generally more expensive than stock, they are very reusable so over time the cost of using them is potentially much less. It is a rare case that these filters ever require replacement and that's usually only if they have been improperly cleaned in gasoline.
Any change in the intake or exhaust system can necessitate carburetor rejetting. Moto Guzzis, though, are among the least effected motorcycles in this regard. Still, a change of this type offers the opportunity to seek a more perfect mixture through a little experimentation. All carbureted bikes will run better with a slight readjustment of the idle mixture screws, usually just a little richer (counter-clockwise). Slightly larger idle jets also seem helpful on V65s and big-valve big twins (those with 40 mm carbs as standard).
Both K&N and Uni filters use suspended oil as the main filtering medium. Both can be cleaned and reoiled almost indefinitely. Both require the use of a special filter oil. The Uni foam filter can be safely and effectively cleaned in solvent. K&N filters should only be cleaned using their specific degreaser. It works best to spray it on, then scrub the filter area using an old tooth brush. K&N filters either come pre-oiled or include a small tube of their special oil in the box. Uni filters should be oiled before use.
The individual filters are designed to attach directly to each carburetor. This requires the removal of the original air box, plus any rubber sleeves that attached the air box to the carbs and also any aluminum adapters screwed onto the carbs' inlets.
On carbureted Guzzi small twins other than the Lario and V65 TT and the T-3, Convert, G-5, SP 1000, and CX-100, the air box also serves the purpose of separating and returning oil breathed out of the engine. That function must be replaced. The usual fix for the big twins is to install the engine breather unit from the LeMans I. A similar devise is available for the small twins.
On some models you will find very little clearance between the filter and either the frame or side cover of your bike. It is essential that the K&N filters aren't allowed to rub against anything solid or they will develop holes over time. There are in some cases smaller filters with added clearance available to fit your carbs. Our testing with an air flow bench has proven that smaller filters do not flow sufficient air, even when new and clean, and therefore will reduce engine power. Because most K&N filters are oval and tapered, it is often possible to rotate them on the carbs so as to reduce or eliminate interference. In some extreme cases the side covers can be trimmed along the forward edge, thereby making necessary clearance without changing the side covers' appearance from the side.
CHS AIFI