So you’ve got the oil warning light on, there’s some strange noises from the engine and you’ve done the oil pressure check on your bike to confirm that there is low oil pressure. Here are some of the common symptoms of low oil pressure and fixes to remedy this – of course you could have abnormally high oil pressure also so you’ll want to check these things as well.
First, before you checked the pressure you would have looked to see if there were any noticeable oil leaks. Have another look around the engine after you’ve run it to double check if there were any leaks. Also note the oil levels, while this won’t effect pressure, just be sure that there is some in there! If it’s low then you’ve got a leak or the engine is burning oil. Of course, you’ll also want to make sure you’re using the right grade oil recommended by the manufacturer as the incorrect viscocity will also cause oil pressure problems.
The most common place for oil to leak will be from the sump bolt itself or from a crankcase gasket, both are very easy to check. While checking the gaskets be sure to look at any oil channels in the engine casings to make sure they’re not blocked – most commonly this will be the misapplication of silicon instant gasket.
Next have a look at the motorcycles oil filter, could be that you need a new one and it’s clogged, not a massive cause of low oil pressure but an easy one to rule out – check the filters bypass valve as well to see if that’s working. Faulty bypass valves can also be a cause of high pressure in the oil system. A clogged oil filter will mean that the oil is no longer being screened so that dirty oil with all the crud in it is going through the engine channels, probably causing a blockage.
Check the head gasket isn’t worn or fitted incorrectly – a poorly fitting gasket can block the oil channels in the engine block, again any instant gasket (if used) could be clogging up the channels. This would be also a good place to check if your motorcycle is burning oil – blue exhaust smoke.
Have a look at the oil pressure release valve, if this is faulty it wil also effect the pressure – most commonly this will be a worn spring in the valve.
Now we’re getting down to the really dirty stuff, by this point you’re going to probably have removed the engine – check the oil pump by removing the sump plate – first thing, have a look at the screen at the base of the pump – is it clogged up with crap? Check there are no obstructions and whether the oil pump is functioning correctly? Check the clearances and any visual damage on the pump.
If you’ve gotten this far then it’s time to check the shell bearings on the crankshaft – they can wear down and an increase in the gap between them and the crankshaft will lower oil pressure, it’ll probably mean splitting the engine case to get at them properly. Also check the crankshaft oil journals to see if there’s any damage there – if they’ve widened that will also lower pressure.
Hopefully by this stage you’ve figured out what’s causing your oil pressure problems. If there is excessive noise from the engine and it does have high mileage, always check the crankshaft bearings as once they start to wear, this will accelerate and just changing the oil pump, filter etc… won’t be enough.