Don't Forget The Oil Screens - Dirt Rider Magazine

Broken clutch plates are one of the most common sources of screen-blocking junk. Sealant, flakes of gasket material and other trash that finds its way into the oil can also cause problems.

An engine's oil pump and the oil screens that protect it are all critical parts of a modern four-stroke that remain largely ignored. Even owners who pride themselves on their maintenance schedule often make this mistake. In the majority of cases the oil pump just whirs along, pumping its little heart out while requiring little to no attention. And most of the time the oil screen will be clean and unobstructed, but if it isn't clean, the results can be disastrous. Most of the latest four-strokes have made the oil screen fairly easy to get to. That isn't always the case, though. Unfortunately, some models have the pick-up screen inside the centercases. If you need to clean a screen inside the cases, it is safest to split the cases to make sure that all of the junk is out of the engine.If you don't see any sign of junk in the oil or filter, chances are the oil screen is clean. But if you have a bike that does not require splitting the cases, check it every so often by taking it out. If you have a bike with the screen inside the cases, try to find an opening that will let you see the screen. That will help ensure that your engine is getting the clean oil it needs at the pressure it wants.

Whenever you change the oil and filter on your bike, look carefully at the oil filter for chips, chunks or pieces deep in the folds. If any show up, you need to inspect the engine more carefully for damage. Generally the screens are in place to prevent large pieces from getting to the filter, so you still need to inspect and clean the screens.
You might also see problems with the oil supply in the cam caps or on the cams themselves. This engine was a little starved for oil. These bearing surfaces should appear perfectly clean and not discolored or marred like these are.
This is the oil pump on a 2007 Kawasaki KX450F. You need to remove the ignition flywheel to get to it. The good news is that this owner has checked the screen before. The bad news is that he didn't pay attention, and part of it is not assembled correctly. Remember how the sheet metal bracket looks here.
Remove the bolts and pull the cover off of the oil pump. Most likely it will be located with dowels, so you'll need to wiggle it a little to work it loose.
This little screen slides in to protect the oil pump from debris. This one is almost perfectly clean, which is just what you hope you see. If the screen is even partially obstructed, your engine can begin to starve for oil to the pump.
Magnetic drain plugs and oil filter magnets are also good indicators of engine health.
This screen from a different bike doesn't look nearly as happy. It has large chips and chunks, though this isn't enough junk to starve the oil pump. This screen is one from inside the centercases. Sometimes you can use a flashlight to inspect the screen through the oil drain plug hole or other openings in the case.
Carefully install the cover and the small sheet metal part. Note that the sheet metal bracket is actually a guide for the cam chain. It was mounted upside down when we first saw it. Make sure to torque the bolts properly.
Some machines have a circular screen like this one. It still has open screen area, but it shows chunks and chips, and the source(s) of that metal must be tracked down and corrected. If the screen is inside the cases and you can see it, it may be possible to break the chips and flakes away with contact cleaner. Then you can flush the pieces out through the drain opening.
The oil pump uses this little impeller, and the clearance between the housing and the end of the vanes is necessarily very tight. Any metal chips that make it past the screen will tear the pump parts up. Put the clean screen back in.
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