The hex drive screwed plug makes the installation and removal of the oil tube, or “sludge trap” much quicker and easier. The design of the original plug with the slot usually calls for the use of an impact driver, which often renders the plug useless after removal. A 10mm hexagonal socket, or Allen key is used to drive the plug in the threaded hole in the crankshaft cheek.
This plug is the correct fitment for the late pre-unit and earlier unit Triumph B-range crankshafts from 1959 through 1968, with an O.D. of 7/8″, 20 TPI CEI threads, and a depth of .416″. May also be suitable fitment for some BSA twin-cylinder crankshafts from 1966-onward. Made in the UK by Hepolite.
The sludge trap resides in the oil passage in the crankshaft between the big-end journals, acting as an oil filter to trap contaminants, and is retained by the top flywheel bolt. The sludge trap plug seals the oil passage. Ordinarily, the plug is replaced is replaced during a crankshaft service.
It is advisable to verify the distance between the oil passage and the face of the bore prior to fitting the plug, ensuring the plug will not block the oil flow to the crankshaft. Once the sludge trap is fitted, and the retaining bolt is torqued to the appropriate specification, the plug is threaded into the bore until it is flush with the crank cheek. It is then staked into place using a punch. Some engine builders recommend the use of thread sealing compound on the plug. Refer to the workshop manual for further details on crankshaft servicing.