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Join Date: Nov 2007
Location: Chandler, Arizona
I am 100% in favor of stock filters, or their equivalent. When you install them, soak them good in oil, and squeeze (not wring) out the excess, but leave them wet with oil. Put some grease on the back edges that seal against the back of the airboxes. A leak is pretty much the same as no filters at all, as is dry foam.
If you want to know the condition of your engine, you can do a compression check, but if it is running and starting good, I wouldn't. Since you already own the bike, if you get low readings, it will just make you feel bad, and there is nothing you can do about it.
Also, readings are just that. I have found a lot of engines that tested terribly, both compression and leakdown. I have seen engines where the valves were not sealing well because the chatter marks from a dull cutter were still on the seats. But they were running just fine.
As for it having been run without filters, it depends on how log it was run that way, and under what conditions. It has almost certainly shortened engine life to some degree, but it may be insignificant considering how long these engines last. The best thing you can do is change the oil right now, then in 500 miles, then every 1000 miles for the next 4-5 times, to help clean out any dirt that may have made it's way into the engine. When an engine ingests dirt through the intake, most of the damage is to the valves, valve seats, rings, and cylinder walls. But some dirt can make it's way past the rings when it gets mixed in with the engine oil, though by then it is usually such small particles it will do little damage. Dirt in the crankcase usually winds up either trapped in the oil filter, or embedded in the bearings.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike