K&N Filters Installation

  The filters I got hold of were labeled ”F021B4” and are ”oval, open-side, universal”, conical,  with the intake hole offset from the center. Top side measures 2” x 3” and the bottom end is 3” by 4”. Diameter of the intake hole was app. 52 mm.  - this showed to be a fairly loose fit and caused no problems in mounting on the carb intake.

Before changing to K&N filters (or at the same time) you should have installed different jet needles and also changed to a more open exhaust system. All according to recommendations from K&N.

First you have to remove the seats and the tank (you will have to do this for just about anything apart from filling gas so go ahead and learn the procedures). Dont forget to turn off the petcock on the tank before disconnecting the hoses. Turn it clockwise to shut it off. I slid a red rubberband over the left hose to remember which hose goes where when assembling. Also remove the side covers.

FRONT AIRBOX
At first glance, I was sure that the front airbox would be hardest to get rid of - how wrong I was.  First, remove the four screws that hold the front tank mount. Also remove the two screws that clamp the throttle cable to the top of the airbox. With a little tweaking and bending of the cables you should have good access to loosen the clamps that hold the intake rubber that connects the airbox with the front carb. Next, loosen the bolts that hold the airbox to the frame. The only one to pose a problem is the front one that is attached from underneath, near the steering head/oil cooler. The best way to reach it is probably to turn the front wheel full to the left and take away the right hand chrome cover of the front cylinder. This will give you enough room. After that you just pull the box out from its position. Next, you have to connect the crank-case breathing tube that goes in to the airbox with the tube that drains it along the left side of the frame - I used a 2” long pipe and two hose clamps for this procedure. Installation of the K&N filter was a piece of cake - just slide it on the carb intake and tighten the clamp. Finally, I used a couple of nylon straps to secure the throttle cable in more or less the same position as it had before.

REAR AIRBOX
The rear box looks easy enough at first glance. However, when you start looking for the attachment points you will find that you must loosen some of the electrical connections that sit on top of the airbox, hiding two of the bolts. They are simple enough to loosen - just some extra time required. Of more importance is the fact that on the left side of the airbox there are electrical components bolted to the box. I would advise against leaving them hanging in air. Also, when you look at the right side of the box there is a ”bulge” that is visible from the outside, sitting underneath the right side cover. This would disappear, leaving a hole, if you were to take away the airbox. My solution was to cut the airbox and leave the side panels and rear of the box, including the fasteners. This gave me a small, hidden compartment where the original filter insert was as well as closing what would otherwise be a ”hole” into the frame. I will probably install a cigarrette lighter here later on. Installing the K&N filter is now merely a matter of sliding it onto the carb and tightening the clamp. You have plenty of room.

The recommendations from K&N on the bypacked piece of paper says that under normal circumstances you will have to increase the main jet of the carbs with 15% after installation of their filters. Say you have a 140 main jet initially - after changing to the K&N filters you would have to increase to a 160 main jet. These are just recommendations and I would recommend doing a spark plug reading test prior to messing with the carbs. If you´re lucky you can get by without changing the main jets.

I run my bike with Jardine 2” drag pipes and have taken out their ”baffles”. I installed new baffles from Highway Hawk instead, thinking that they would provide for some backpressure as well as lowering the noise level somewhat.

Shortly thereafter I experienced something interesting - without knowing it I lost one of these baffles. The ride turned out to be very rough with lots of misfiring and loss of power. This indicates too little fuel - conclusion: IF YOU RIDE WITH OPEN DRAG PIPES, INCREASE THE MAIN JETS!! A friend of mine had found the baffle and came over with it. After installing it I took the bike for another spin and everything was fine again!! So, for my 1400, I believed everything was fine without having to rejet - as long as I kept the baffles  -  WRONG!!

I recently had the bike tested in a Dyno bench with the following results:

First run 1) Dynojet needle kit, stock main jets, K&N filters, 2” drag pipes with baffles
The bike ran fine up to when the main jets governs the fuel inlet. Then the ignition curve became ragged (uneven combustion) and the maximum power was no more than 46.5 hp´s. (And I thought it ran great!) Torque 82.5 Nm maximum.

Second run 2) Same as for the first run but with the main jets changed to Dyno jets – 150 up front and 160 in rear.
Immediately there was a much smoother ignition curve, indicating a better running engine. Max power increased to 50.6 hp´s while the torque actually went down to 80.6 Nm

Third run 3) Finally I removed the baffles to see how much they influenced the effect – that did it!
The effect curve was smooth as a babys butt and peaked at 64.4 hp´s at the wheel! With a torque of 109.8 Nm

This was actually slightly more than what they had achieved with another 1400 the other day – with V&H slipons which is supposed to be the best. The difference when I rode home was more dramatic than I had expected. The big kick in the pants now come from 60 mph and up and thats just where I want it to be. Good for when you´re passing other traffic. Top speed actually increased as well – this must be due to a smoother running engine that´s not stuttering and starving for fuel, since the rev. limiter still is the same. No problems hitting the ”century mark” whatsoever.

Is it worth all the extra trouble?  -  that is something you have to decide for yourselves. I do enjoy the extra kick in the butt, though.