Looks just like my stock '91 FXSTC cleaner except for the extra holes drilled in the backing plate. Sold the bike a couple years ago. Had Python II exhaust, but kept the stock air cleaner. Thought it looked OK and really was no need to go bigger. The air cleaner was big enough as it was, IMHO. I don't think an air cleaner change would matter on your Evo... they were fairly free flowing stock.

 

There is a good article in this month's American Iron that you should check out. One of the biggest advantages of a true high performance air cleaner is not only the massive openings around the filter, but more importantly the smooth radius and air entry of the backplate. Around the opening of the carb, the back plate should be a smooth radius to keep air "laminate" not "turbelent".

Here is my example:

http://s2.largeimagehost.com/HL/UXUUteF/DSCF0004.JPG

Notice the smooth turn into the mouth of the carb. Your stock backplate won't be as smooth.

I went from a modified stocker (kinda like yours) to the Arlen Ness set -up and I noticed a difference. It was enough difference that I had to change the pilot jet up to a bigger size in my carb.

 

If you will notice that when you install the filter that the opening on the back side of the filter, which is a metal plate, actually fits perfectly over the intake opening. No way for air to bypass the filter. Those holes aresupposed to be there, they let the air in and around the back side of the filter.

 

Thanks for the additional input! I appreciate it.

Chris

 

To add to this....

Originally I followed the advise of a well respected forum memebr and cut the most of the plastic backing out of my stock airbox. As long as the filter element is sealed over the carb opening you will have no ill effects.

 

Thanks. I think I'll drill a few more holes in it for sh*ts and giggles. May not make any difference at all, but it gives me something to screw around with that I most likely won't mess up. lol...

 

As long as the back of the filter seals around the intake(flat area)in the first pic your good to go.Drilling more holes wont do anything except make the housing weaker IMO.

 

better plug those holes they are on the inside of the filter element . yes that would be aconsidered a high flow but also high bugs dirt sticks sand anything else that would normally be stopped by the filter element. might as well run no filter at all as that set up sorry.........

[IMG]local://upfiles/5757/F0BCC1DC954F4AAA9F1FF0CEAFB897A3.jpg[/IMG]

 

Keep reading... It's fine.

 

That a stock filter too right? Do you know if the bike has been rejetted? You can take off the carb bottom and look at the jet sizes with a flashlight from underneath real quick to tell. If it hasnt been rejetted. A highflow air cleaner and tuning will net you prolly 8 rear wheel horse power which you will definitly notice.