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Thread: Valve shims
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post #15 of Old 10-15-2018, 03:17 PM
2nd Gear
Join Date: Jun 2017
Posts: 320
Originally Posted by pdwestman View Post
Voyager, One test of automotive air filters vs 48 years of work experience on motorcycles with all different types & brands of air filters is not enough to change my opinion when it comes to motorcycle air filters.

Have you also noticed that Uni-Filter brand is the most open pore design of all major brand of oiled foam air filters which I am aware of?

I actually prefer the finer pore OEM or TwinAir or similar which work Very Well with SAE 40 or even 10W40. (Yes, I know the engine oils migrate inside of the air box, but easier clean-out than sticky stuff.)

I really like the Kawasaki road bike & atv fine pored oiled foam filters which have 1/8th inch tall Yellow Hair on their exterior. They should have used that material for all Kawasaki product, IMHO. The Hair reduces plugging of the foam pores, which allows easier air flow and longer service interval. And works very well with engine oils.
I am also using 49 years of experience with motorcycles, chainsaws, lawn equipment, heavy machinery, and two engineering degrees. And this is one test of many. I have never seen a single test where a foam filter captured particulates better than a paper element. If you are aware of such a test, I’d appreciate a reference. The main drawbacks of paper element filters are cost and lack of water resistance, however, some synthetic media now is pretty good in the latter regard.

You mainly find foam on small engines that will not see the hours or miles of most larger vehicle engines. Or as a prefilter before a paper element to catch the larger debris and extend the life of the paper element. The reality is that most off-road motorcycles will not see 30,000 miles and most lawnmowers similarly wont see 1,000 hours of operation. In those scenarios, the extra dirt passed by the foam filters won’t make much difference. It probably takes 50,000 miles or 2,000 hours before the lesser wear from the better filtration of a paper element begins to make a practical difference.

However, we each get to make our own decision in many cases. If an engine comes with foam, I stick with that. If an engine comes with paper, I stick with that. I will never switch from paper to a K&N foam filter. Some engines, like the Kawasaki’s in my John Deere’s, have the best of both worlds: A paper main element with rubber gaskets to provided excellent particulate trapping and a foam pre-filter to catch large stuff like bugs and grass and any water that may be ingested.
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