Motorcycle engine repair can be a frustrating chore, especially when the problem has to do with the oil pan or sump. The oil pan is the part of an engine where the oil drains to and where it is stored. In a wet sump engine, an oil pump injects oil into the various bearings of the engine. The oil is then allowed to drain down to the bottom into the oil pan. Problems that arise in this part of a motorcycle are usually first noticed when oil is found leaking out of the bike.
Step 1 – Check the Plug
If oil appears to be leaking onto the air filter or other parts of the motor, the problem may be a poor seal around the oil drain plug. The oil drain plug is located at the bottom of the sump and should be fairly tight. If the plug appears loose, unscrew it and apply some Teflon tape around the threads. This should make the seal around the plug much tighter.
Step 2 – Replace the Plug if Necessary
If the sump plug appears to be stripped when it is removed, then it was probably over tightened after the last oil change. To fix this problem, first run a thread chaser or thread tap through the oil drain to remove any obstructions or burrs that may interfere with the plug rethreading correctly. Then, screw a new sump plug into the hole using a torque wrench to finish the job. Do not tighten the plug to more than 40 nm’s or 29.5 ft/lbs of torque. Doing this will likely re-strip the plug.
Step 3 – Replace the Crush Washer
A crush washer is found beneath every oil drain plug. It is a wavy ring made out of either copper or aluminum that deforms as pressure is applied to it. The process of deforming the washer helps form a seal around the plug. Because the washer changes its shape as the drain plug is tightened, it must be replaced each time the oil is changed. If oil is leaking from the sump, replace the crush washer to ensure the seal around the plug is tight.
Step 4 – Check for Cracks
If oil is leaking, but the seal around the drain plug is working properly, there may be a crack in the sump. Check carefully around the sump looking for hairline stress or heat fractures. If a crack is found, use a socket wrench to unbolt the sump from the frame and remove it from the motorcycle. At this point one has a choice to make: either buy a new sump, or repair the damaged one. A new sump usually costs quite a bit of money, but repairing it will require some welding tools and skill or a trip to a local mechanic or welder. It is up to you which is the most effective means of repairing your motorcycle.