Aftermarket replacement foam air filters...

[tmacey45]

Hey fellow GS'ers,
Not really sure where to put this thread, but it may be useful to someone working on an older bike using newer foam type air filters...As I mentioned before, right after rebuilding the carbs on my '82 GS1100GK, I had an issue with it spitting/sputtering at 3/4 throttle and beyond. Today I found the reason. After searching for a new air filter on eBay, I noticed that the ads for the K&N foam type filters mentioned it may be necessary to rejet carbs because of the increased airflow in their brand of filter. Today I pulled the air filter out of my bike and sure enough, it's a K&N brand filter. So I decided to do an experiment. I took a piece of (soft) packing foam (that an LCD monitor was packed in) and cut it to fit INSIDE the air filter's frame ( it kind of looks like a small cage and the air filter itself goes around it). I seated the K&N filter back on to the filter frame, then inserted it back into the air box. Because there was a screen on the top of the frame, there is no worry about the foam piece getting "sucked" up into the intakes. It restricted the air flow of course, thus getting it closer to the OEM paper element filter's air flow specs. Well, it worked! I opened up the throttle (full) and off she went... no spit, no sputter, it just took off like a bat out of hell...My bike is now running PERFECT! It's a quick easy way to fix the increased air flow these newer foam type air filters cause without re-jetting. Thought this might be helpful to someone and wanted to share ...Tony

 

[Dogma]

Good one. You might do some testing on the scraps to make sure the foam you used won't eventually disintegrate in the presence of fuel vapors and oil.

 

[tmacey45]

Good one. You might do some testing on the scraps to make sure the foam you used won't eventually disintegrate in the presence of fuel vapors and oil.

You're right Dogma, I will take it out and replace it every other month (until I run out of this foam material). Or, until I find some foam material that's made specificly for this type of application for a more permanent fix...

 

[Dogma]

UNI makes a foam filter that's been on my mind for a while My 850 has on. My 1000G project bike has a K&N filter (look like one, anyway), and I'm wondering if that might flow too much, or if a PO had done the work to make it run correctly. I guess I won't know until I finish putting it back together.

 

[bwringer]

The green Uni foam filter for the shafties is a pretty standard replacement. Works great -- just don't over-oil it.