I believe that check valves are very common in most filters including the stock one. If you look at the oil flow path and direction - from the sump to the pump to the filter and then to the various engine parts like bearings and the top end which are all under pressure, once it lubricates the required parts it drains to the sump generally not under as much pressure from the oil pump, the topend drains mostly by gravity and does it all again in a loop - All the check filter will do is prevent backflow from these points through the filter and taking junk back out of the filter into the sump, sort of unfiltering the oil. All the oil in the topend will still drain just fine through the oil passages to the sump just like normal wether the engine is running or not, so there will be no problems with the measuring the level. If it is mentioned on the filter package or in K&N advertizing as a special feature it is merely advertising hype. Hope this helps. Terry
I just changed my oil and installed a K&N oil filter. The filter has a check valve that prevents all the oil from draining out of your top end after the bike is shut off. This makes terrific sense, because the oil (theoretically) stays up in the head to prevent damage upon start-up. Right away it seemed to be working, and herein lies the problem: how does one check oil level at the sight glass if all the oil is stuck up in the engine? Is anyone else on the list using these filters and have a recommendation? With the correct amount of oil in the engine, and after shutting down, the oil level in the sump is just a little below the bottom of the sight glass window. Is this my new "full" mark? Can anyone with deep engine knowledge say whether it's really an advantage (more than theoretically) to trap all that oil up in the engine? I really just wondering if the extra $10 for the K&N filter is worth it. Strange, there was no mention of this "new oil level thing" on the K&N filter packaging. Someone with slightly lower critical thinking skills than me (not a stretch) could easily become confused and just keep adding oil until the level looked right. I'm guessing that on the GTS that would be at least a quart too much oil! The difference between perseverance and obstinacy is, that one often comes from a strong will, and the other from a strong won't. -Henry Ward Beecher [EMAIL PROTECTED] || http://www.huntel.net/terryth
