5.04. Air Filters

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See also: 2.17._Air_Filters

The air filters for the XS650 varied widely from year to year. The 1976 model uses a very hard to find type of oil/foam filter. Replacements are made, but can cost almost $100 each. The original filters can be (heavily) modified and rebuilt. First, I ripped off all the foam/fabric, and then blowtorched the edges to melt away any remaining bristles that might get sucked into the engine. I cut away all the wire mesh, and cut up a new car air filter--the type with the folded white paper ($5). Leaving one side connected to the frame, I then glued the filter to the frame of the old filter, so that the filter would fit snuggly over the carb's intake, and epoxied a makeshift frame around it to keep a good seal. I made a little spring to hold the filters in place over the carbs. In all, I spent less than $6 for the filter and epoxy and about an hour of work to replace the filters that would have been $175 had I gone with K&N--the only brand I could find to make replacements. Several hundred miles later, they're still working perfectly.

5.04.01

This Filter fits in the original Filter boxes

Needs a little modification though (few Millimeters of plastic board that its not loose)

www.jsesc.com - Stens Air filter

Another seller

www.mowpart.com


5.04.02

K&N Recommendation


With the K&N pods, a number starting in RC indicates a chrome end cap and one starting with RU, a rubber one. You can get most of them either way. They recommend the RC0982 (chrome end cap) for the 650s but you can get these with rubber end caps (RU0982). These filters have a 54mm I.D. mounting flange and fit the BS34s well but are a rather loose and sloppy fit on the 52mm O.D. of the BS38 carb intake. For those, I prefer the RU1822 filters as they have a 51mm I.D. and slip on the 38s nice and snug. They share the exact same filter body with the 0982s, the mounting flange I.D. is the only difference.

I also prefer the RU over the RC style. The rubber end cap on the RU type is a full 1/2" taller and wider than the chrome metal end cap on the RC so you get a slightly larger filter.


Bob

bmwbobz@msn.com


I have a 1979 and both air filters were shot. These filters are metal cages with a thick velvet fabric stretched over them, but the fabric had rotted and ripped badly.

I cut away all the fabric so I was just left with the short metal screen tube with two metal end caps, one cap with the hole that let air into the carbs.

I bought electrostatic filter cloth for a hammock style furnace filter and cut a strip to wind around the metal mesh. I wound around a few layers and used a few elastic bands to hold it in place. So far it has worked fine, but I had to experiment a bit to see how many layers of cloth worked the best. The permeability of these filters affects the mixture a lot and I found that if there were too many layers of cloth the bike ran rough and too few the bike ran lean and overheated.

I can't vouch for the air filter effectiveness but the bike runs well with them.

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