Royal Enfield 500 TWIN 1949, Workshop Maintenance Manual

Page: 8 / 110

ROYAL ENFIELD WORKSHOP MANUAL
SECTION B1
Engine Specification
"Meteor 700" and " 500 Twin"
1. Engine
The engine is an even-firing vertical twin
cylinder, having separate cylinders and heads
and fully enclosed pressure-fed overhead valve
gear. It has dry sump lubrication with the oil
tank integral with the crankcase and a massive
one piece high-strength cast iron crankshaft.
2. Cylinder Heads
The cylinder heads are die-cast from light
aluminium alloy with ample finning to ensure
adequate cooling. The exhaust pipe inserts are
cast in and the valve inserts are of austenitic iron
and are shrunk in so that they are replaceable.
Steel wire thread inserts which are easily
renewable are provided for the sparking plugs to
prevent damage to the threads in the heads. The
large capacity induction ports are stream-lined
and blended to the valve seatings.
On very early models, the cylinder heads
were sand castings.
3. Cylinders
The cylinders are separate and of cast iron,
with internal tunnels enclosing the push rods.
The cylinder heads are located by spigots on the
cylinder barrels.
“Meteor” Engine. The nominal bore is 70
m.m. and the stroke 90 m.m., giving a cubic
capacity of 692 c.c.
“500 c.c. Twin” Engine. The nominal bore is
64 m.m. and the stroke 77 m.m., giving a cubic
capacity of 496 c.c.
4. Pistons
The pistons are of low expansion aluminium
alloy, heat-treated and form-turned oval and
having split skirts. The compression ratio is
6.1/2 to 1 in the “Meteor” engine and 7.1/2 to 1
in the “500 Twin.” There are three piston rings,
the top two of which are compression rings.
Both are taper ground and the top one is
chromium plated. The third ring is for oil
control and is slotted.
5. Connecting -Rods
The connecting rods are produced from
stampings of Hiduminium RR56 light alloy. The
little end bearings are of alloy direct on to the
gudgeon pin. In case of wear after long service
the little end can be bored out and fitted with a
bush, but this is rarely necessary.
The big end bearings consist of
white-metalled steel liners which are renewable.
The detachable bearing caps are bolted to the
connecting rods by means of high tensile socket
screws, secured by cotter pins. Some earlier
models have bolts and castle nuts.
6. Crankcase
The combined crankcase and oil tank are
die-cast from light alloy in two halves, being
split vertically.
7. Crankshaft and Flywheel
The crankshaft is cast in one piece, integral
with the massive central flywheel, from high
quality cromol or mehanite cast iron. The total
weight is 26 lbs. and it is carefully balanced.
The main journals are ground and the big end
journals are ground and hand-lapped.
8. Main Bearings
Heavy duty bearings are provided for the
crankshaft, the driving side being ball and the
timing side roller.
9. Camshafts
The camshafts are machined from
drop-forged steel stampings with the cams and
bearings hardened and ground. The cam profiles
are produced with silencing ramps to ensure
quiet running.
10. Valves
The inlet valves are machined from
stampings of special Silicon-Chrome Valve
Steel and the exhaust valves are of High
Nickel-ChromiumTungsten Steel.
11. Valve Gear
The valves are operated from the camshafts
by means of large flat-based guided tappets,
alloy push rods and overhead rockers. Two
compression springs are fitted to each valve.
On earlier models, steel push rods were used.
12. Timing Drive
The camshafts are located in the crankcase,
running in bronze bushes. They are driven by a
Section B1 Page 1
www.hitchcocksmotorcycles.com