Sludge Trap Tube Information
The Sludge Trap
Original Triumph drawing showing how the oil flows inside the engine. Notice the sludge trap tube.
The Triumph sludge trap system is a simple yet effective design when its in proper working condition. The sludge trap acts as a centrifugal oil filter which prevents dirt, sludge, and unwanted debris from entering the crankshaft and working its way into the journals and rod bearings. Oil is fed through the end of the crankshaft (timing side) and forced through the rod bearings. Excess oil falls to the bottom of the crankcase (sump) and gets picked up by the scavenge (return) and works it's way back to the oil tank.
"The oil pump is the heart, oil is the blood, sludge is a clogged artery..."
The fault of the sludge trap design is that you can not physically clean the tube unless you split the cases. Splitting the cases means to separate the two engine halves. In other words, a full rebuild. When your rebuilding a Triumph or BSA twin it is mandatory, a must, to remove the screw, extract the tube and clean out the sludge trap. Those that fail to do this will suffer. Look at it this way, the oil pump is the heart, the oil is the blood, and sludge in the tube is a clogged artery.
A true Triumph "barn find". Do you think the sludge trap is clean or packed full?
If you where able to obtain an original "barn find" motorcycle that has not been running in years or perhaps decades, chances are the sludge trap could be full of sludge and grime. How would you know? Its really a risk you take when getting the bike back on the road. Unless the motorcycle was well maintained then you should not have any issues. When the motorcycle is running, remove the oil cap and take a peak inside the tank and check the return flow. You could always check the oil pressure PSI rating on later unit models.
You should always change your oil by the recommended mileage especially if your motorcycle has a sludge trap or has been recently rebuilt. When motorcycles sit for long periods of time or when the oil is rarely changed it can do more harm than good. Particles and debris in your oil can scar the crankshaft journals. Have you ever took apart an engine and noticed vertical lines on you crankshaft journals? That is from the debris circulating in your oil!
A classic example of a clogged Triumph sludge trap. Keep your oil clean and changed regularly.
There is a lot of hype on the internet about the sludge trap design. Its not the best design but the theory works when its well maintained. Its true, if your sludge trap is packed full of grime and debris to the point where it restricts oil from the rod journals and connecting rods, it could seize and perhaps cause more damage to your engine.
There are 2 ways to get the maximum life out of your engine. Change your oil every 1,000 miles using a high quality brand name oil (non-synthetic) or install an in-line oil filter on the return line and change it every time you change your engine oil. If you follow those two steps your bottom end will last you a long time. Remember, oil is a lot cheaper than rebuilding your entire engine, again.