Triumph Thunderbird Service Manual page 144

Lubrication
Oil Circuit
Oil is collected from the sump and is drawn through a mesh strainer into the oil pump rotor. The oil pump is fitted with a
single pumping rotor which supplies pressurised oil to the lubrication circuit. The oil circuit is split into two parts - the Main
circuit and the Transmission circuit.
Main Circuit
Pressurised oil flows past the oil pressure relief valve, which controls the maximum pressure in the oil circuit. The relief
valve is set to open at 5.1 bar (74 Ib/in
2 )
and when open, returns high pressure oil directly to the sump.
From the main oil circuit, some oil is fed to the balancer shaft thrust face spray jets. The oil in the main circuit then flows
through the oil filter, after which another branch supplies oil to the hydraulic camshaft drive chain tensioner.
Filtered oil is then fed into the lower crankcase gallery. The low oil pressure switch is located in this gallery. From here oil
is distributed around the engine:
Some oil is sent directly to the cylinder head via a drilling in the upper crankcase. Oil that arrives at the cylinder
head is fed to both camshafts via galleries in the camshaft ladder castings that deliver oil directly to the camshaft
bearings. This oil also lubricates the tappet buckets and the valves.
Oil from the cylinder head area lubricates the camshaft drive chain before draining back to the sump.
The remaining oil is sent directly to the main gallery located to the rear of the cylinders. Here it is delivered to
the crankshaft main bearings and, via drillings in the crankshaft, to the big end bearings.
Spray jets located in the upper crankcase, behind the main bearing shells, lubricate the pistons and connecting
rod small ends. These jets are fed oil from the crankshaft oil feed.
Oil is also fed to the alternator spray bar to aid cooling of the alternator. The oil is taken from the crankshaft oil
feed and directed to the alternator stator and rotor.
Transmission Circuit
Pressurised oil is fed via a pipe from the oil pump to the gearbox spray bar, where oil is directed via drillings to
the input and output shafts and the clutch. Oil is circulated along the gearbox shafts to exit holes that feed
directly to the bearings, gears and selectors. The gearbox spray bar also lubricates the gears and selector forks
and selector drum.
8.4
SelVice Manual - Thunderbird