Has anyone tried using a RU-2970 K&N air filter?

Awesome. I may have to go this route myself. Is there room for a crank case breather under this filter?

 

that's cool, i did see that before and wondered if it fitted!

 

Awesome, I've been wanted to take another route instead of using 2 pods. A single unit is more what I wanted. Great find, thanks a ton.

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I know this is an old thread, and Im new so sorry. but where is your battery then?

 

After reading this thread, i bought this airfilter too, and i am very pleased with it

I found a alternative battery and gave it a new location
After cutting away a bit of plastic.




I cut away 6 mm of the airfilter rubber mountings. This way the lip inside the filters will sit flush with the carburetor intake.

 

Looks cool!

 

Lasse, just out of curiousity, what are the specs on that battery - can't quite read it. I've been looking at doing just that with my battery but was not sure if those type batteries could handle the current draw of headlights + ignition + turnsignal + tail light etc...

Gotta see Denmark one of these days - a few years ago I learned my last name (Davidson) was originally Davidsen (obviously Danish) but Elis Island botched it when my ancestors came to the U.S.

Cheers!

- James

 

I'm running a 1.5 aH 12v AGM battery even smaller than that one and have had no problems, but my bike is kick only. I actually removed the starter relay in the process of wiring in the terminals for the battery. If you want to retain e-start it will be difficult to keep a battery like that healthy.

 

The biggest thing with the smaller batteries is the charge cycle of it. These bikes put out 14.5-7 volts at 5k rpm's. A lot of the little batteries can't take that much and get fried after a while. My 80 has a 1.2ah sealed acid battery that I have been using for 3 years in this bike and 2 years in one of my razz's with about 6k miles total and still holds 12.6v after sitting for weeks. It sat all last winter (in a warm dry basement) without any charge and still had 12.5v come spring. Not bad for a $9 battery.

 

I was wondering, since there is a ton of air flow from that type of filter, could you fill in every other "notch" (for lack of a better term) with some type of filler like maybe JB weld or RTV or something? I would think that would cut down quite a bit on airflow. Thoughts?

 

Sure you could but your better of going stock or jetting to match.

 

Here´s the specs on the battery
http://ultracell.net/datasheets/UL2.4-12.pdf

It's 2.4AH capacity and i have no problems with powerloss (kick start only)


A last name ending with "-sen" sounds very danish i agree, that's also the case with my own last name

 

After some years, how is it going with the air filter? Did you rejet or keep your cabrs stock? Do you recommend it?

 

I am doing the same kind of thing. But I just cut out the front of the air box, so the battery can stay in the same place. Have two EMGO filters to pick up next time I am on the mainland. I will check to see how much water gets sprayed around the filters. If too much I will change to the double foam type filter. They should not mind touching the frame, located just above the filters. I have 4 1/8 inches from the carbs to the filter box. I will use a longer piece of rubber tubing for the crank vent and locate it elsewhere on the air box. Later I may change to a small filter directly to the crank casing. If there is room. I have main jets in 117.2 122.5 125 127.5 130 and 140.
First test will be with the 125 in each carb. Mine is a DOHC motor. 83 Seca.

Unkle Crusty

 

Hello,
My name is Alex, I know this is an old topic but I hope someone will find this post and help me

I've recently bought an 1981 XS400 Special 4G5 and I've mounted K&N RU-2970 air filter on it.
Did you guys rejet the carbs ?
Can you please tell me what modifications should I make to run well ?
Sorry for my bad english...
Thank you !

 

K & N Air Filters ?....judge for yourself.....
Air Filter Tests....some pretty good info here.....https://nicoclub.com/archives/kn-vs-oem-filter.html

 

For most people's motors OEM is best.