Description; Camshaft Cover; Removal - Triumph Thunderbird Service Manual

Description
The engine is fitted with an aluminium alloy cylinder head,
which carries the camshafts, valves and spark plugs. The
cylinder head is cast as a single entity, to which various
components are permanently added after machining.
A silent-running camshaft drive chain drives the
twin-overhead camshafts, which run directly in the
cylinder head without additional bearings. The crankshaft
drives an idler gear, which in turn drives the camshaft
drive chain. The idler gear, and therefore the camshafts,
rotate in the opposite direction to the crankshaft.
The engine is fitted with a camshaft drive chain hydraulic
tensioner. The tensioner is fed oil via a gallery in the
crankcase. The combination of oil pressure and spring
pressure pushes the plunger against the tensioner blade
which tensions the camshaft drive chain. The hydraulic
tensioner has an oil pressure relief valve located in the
plunger that is set to open between 12 - 16 bar. The chain
is guided by two nylon tensioner blades. The rubbing
blade is located in the crankcase by lugs on the blade. The
cylinder head must be removed to remove this blade. The
tensioner blade is secured to the cylinder head by two
bolts at its upper end, and its lower end rests on the
tensioner plunger.
The exhaust camshaft is fitted with decompressors on
each end. These decompressors use a small camshaft to
open the outer exhaust valves at low engine speed to aid
starting performance. Once the engine has started, fly
weights on the decompressors are thrown outwards by
centrifugal force, rotating the cams away from the exhaust
valves. The engine will then operate in the normal way.
Valve clearances are adjusted by changing variable
thickness shims that sit between the camshaft and valve
tappet bucket. The valves are fitted with single,
symmetrical valve springs. Both the tip and seat face of the
valves are hardened to give a long service life. Due to the
assembly methods used, the valve seats and valve guides
cannot be replaced.
Oil is supplied to the cylinder head by an internal
passageway inside the engine. Once it arrives at the
cylinder head, it is passed through a restrictor, and is then
delivered to the camshaft bearing journals along grooves
in the camshaft ladders. The camshaft lobes are splash fed
by oil coming from the camshaft journals.
Cylinder Head
Camshaft Cover
Before starting work, ensure the motorcycle is stabilised
and adequately supported. This will help prevent it from
falling and causing injury to the operator or damage to
the motorcycle.
Removal
1. Remove the rider's seat (see page 17-8).
2. Disconnect the battery, negative (black) lead first.
3. Remove the fuel tank (see page 10-86>.
4. Drain the cooling system (see page 11-6>-
5. Remove the upper coolant tube fixing bolt.
)
\1\
1. Upper coolant tube
2.
Fixing
6. Release the hose clips securing the upper
coolant tube to the thermostat housing hose, top
hose and radiator cap housing hose.
7.
Ease the upper coolant tube upwards at the rear to
release it from the thermostat housing hose.
8. Release the coolant tube from the radiator top
hose and then the radiator cap housing hose.
9. Remove the upper coolant tube upwards through
the frame rails.
10. Remove both MAP sensors, noting the routing of the
MAP sensor hoses and harnesses (see page
10-100>.
SelVice Manual - Thunderbird
3.5