Uni Filter fitment

[Excess Impulse]

I have been looking through the posts on aftermarket pod filters, and want to ditch the stock airbox on my 1980 XS400. Looks like the ones from Mike's XS are junk, and Uni's are the way to go, but the red paper type (RC 130/2) are difficult to find. I see some on ebay that are the 52mm ID, Uni #NU4001. These are 5.75 inches long, and another Uni filter that is 52mm ID (PK-82) that is 3" long. My question is, has anyone used either of these, and would either of them work? It sounded from reading the forums that the long filters are better? I will be using the stock H pipe and stock exhaust(for now).

 

[Excess Impulse]

I'm thinking of getting the shorter 3" ones, seems the 5.75" would be too long.

 

[xschris]

Short ones and long ones. 4" and 6" Both mounted on xs360 H-pipes which are a bit longer than the xs400 one.

 

[Excess Impulse]

Thanks for the pics, nice to know they will both fit, though I still like the shorter ones best myself, I will have to get a pair as I don't want to use the stock ones.Ultimately I'd like the reusable K&N style, or UNI's.

 

[xschris]

This is how I connected them. It destroys the stock filter, but I had an old set and it holds them well.

 

[Excess Impulse]

Nice, that gives you a good flange to mount onto. I did some shopping on ebay and ended up ordering a pair of K&N RU 0500 filters. I already have a recharging kit, and believe these filters should last a long time. Maybe I can use your trick to mount the K&N's, will see how they fit when they arrive. They are 52mm ID.

 

[xschris]

I used the RD-0510 K&N's on my 80. They are 54mm id 5" long and have a 22mm length flange. The longer flange gives it a longer bite on the iner metel pipe and the outer rubber H-pipe. K&N filters will out last the bike if you take care of them.

 

[Excess Impulse]

Had a little time today, and cut up the original filter to use the metal tube for a "no crush" support. This is such a great idea! Things like this is why this is an awesome forum. And, if I ever wanted to return to the stock filters, I kept the housing so I'd just need the filter insert I suppose.
From what I have been seeing, it's a good idea to keep the stock "H" pipe, but some have used the UNI filters right on the carbs and deleted the "H" pipe. Is this a tuning issue, or what exactly does the H pipe do? Is it really needed?

 

[xschris]

Keep the H-pipe. Makes tuning much better. Also with the crank vent tube attached it adds support to the carbs.