Harley drain plug installation is not difficult but things can quickly become difficult if a drain plug is installed incorrectly. If a drain plug is not installed straight or is installed dirty, the plug’s threaded allocation in the case can become permanently damaged. The most common way oil cases become damaged is from Harley drain plug over tightening.
If the engine oil or transmission oil drain plug allocation becomes stripped on a touring model, the entire oil pan may need to be replaced. This holds true for, both, Twin Cams and M8 Touring models. If the primary drain plug allocation becomes stripped, the inner primary case may need replacement.
Sometimes, an oversized Harley drain plug can be used to repair a case. However, if an oversized drain plug is to be attempted, we strongly suggest removing the damaged case from the motorcycle. If “fitting” the oversize plug with the case still installed, you will run the risk of aluminum debris entering the oil compartment and, later, contaminating the oil.
That being said; Harley drain plug installation or oil change in general, should only be considered an easy service point by an individual if it has been completed many times, with a perfect end result.
It is of utmost importance to remove the engine oil and transmission oil fill plugs along with the primary derby cover; either before draining the oils or before the drain plugs are reinstalled.
This will help to avoid confusion as to whether or not the oil has been replenished before attempting to start the motorcycle.
Remember to replace the drain plug o-ring every time the drain plug is removed. The o-ring can give a false sense of feel when tightening. It can be confusing trying to determine if the drain plug is tightened enough. This is where it is easy to get into trouble and over tighten a drain plug and this is why it is so important that a torque wrench is used when tightening your drain plugs. Tighten your drain plugs 14 to 21 foot pounds.