This is the correct primary chain tensioner blade trunnion for the 1966-1967 Triumph 350 and 500 models, as well as the 1966-1972 Triumph 650 models with the duplex primary drive chain. Also specified for fitment to the dual tensioner blades fitted to the 1969-1973 BSA A75 and Triumph T150 triples with the triplex primary drive chain.
The trunnion serves as a guide for the primary chain tensioner adjusting tie rod. Overall length is 1-1/4″, with an OD of 3/8″. Made in the UK.
The correct length of the trunnion is important to achieve the proper alignment of the tie rod. Some suppliers supersede the shorter 70-4148, as used on the early unit-construction Triumph twins, to 70-5977, although they are different parts.
The trunnion is captured in the looped end of the primary chain tensioner blade. The primary chaincase cover must be removed to access the chain tensioner system. Refer to your workshop manual for detailed procedures.
