Speedway Workshop

Weslake SOHC Manual, Part 2

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ADJUSTING PROCEDURE:
Run part of the track at full throttle. After a quick closing of the throttle and stopping of the engine (the engine must not be permitted to idle) ascertain whether the jet is suitable If the jet has been chosen correctly, the piston head shows a slight moisture, with traces of oil and it has a golden discolouring. If the jet -is too small (lean mixture), the piston head is dry and greyish. The same symptoms is also shown by the spark plug. If the jet is too large (rich mixture), there are traces of fuel on the piston and the spark plug. After a correct determination of the jet size, which is the most important part of the carburettor adjustment, adjust the idling screw and the metering (throttle) needle. The highest engine power output can be attained only with a carburettor adjusted in this way. To avoid a risk of the piston getting burnt through, it is recommended to use a jet larger by one size. The power output of the engine will drop only imperceptibly.


ADJUST THE CLUTCH:
The clutch is a multiplate one. It's correct function depends on correct clutch disengagement. In declutching, the pressure plate must get apart uniformly from the friction plates, which is obtained by a uniform tightening of the spring nuts on the clutch cover.
Correct function of the clutch is checked in that the clutch is disengaged and the rear wheel is revolved. The wheel must spin freely.


ADJUSTING THE IGNITION ADVANCE:
Full performance of the engine depends on the correct adjustment of the ignition advance. The advance is 35o B.T.D.C. of the compression stroke of the piston. It is also very important that the special rechargeable high voltage ignition-box is correctly maintained and fully charged.

CHARGING INSTRUCTIONS-TYPE SPY 5 L-MODEL 1982.
l: DO NOT use a battery charger for re-charging. (Mains charger available on request).

2: Charge up unit from a 12 volt car or motor cycle battery i.e. direct from a motor vehicle battery.

3: A unit requires 75 minutes charge prior to first race meeting. From then on,Re-Charge unit for 60 minutes prior to each race meeting. This is more than sufficient for a complete meeting. There is nothing gained by charging unit longer than 60 minutes.

4: A fully charged up unit will run for 45 to 50 minutes continuously at maximum rpm's 12.000+.

5: DO NOT switch unit on and off unnecessary, with H.T. lead, C.B. and earth wires disconnected, as undue stress is placed on component parts of your unit.

6: Black = earth. - White to points. - Green/yellow to ignition cut-out.

7: Adherence to the above rules will ensure long and trouble free service from your 1982 Interspan unit.

LUBRICATING THE ENGINE:
The lubrication of the engine is of the total-loss type, i.e. oil that passed through the engine does not return into the oil tank but leaves the engine through the venting valves in the bottom of the crank-case. For this reason it is necessary to check the amount of oil in the oil tank after each race heat.

The oil delivery pump is of dual feed. The outer pump delivers the oil to the head, and inspection window serves the purpose of checking the amount of oil delivered. The oil feed to the big end is not adjustable but the flow to the rocker gear may be varied by means of the adjusting screw and locknut on the pilgrim pump. Screw "out" for greater supply and in for less. At the works these units are set so that the oil supply visible in the transparent rocker feed pipe has 1/4" breaks between oil "slugs". If feed is reduced below this point the valve gear will suffer. If the pilgrim pump is dismantled careful note should be made of the position of the plungers as they are "handed". Incor- rect re-fitting will cause serious damage. It is recommended to make use of CASTROL-R 40 OIL. The disadvantage of this is its vegetable base origin, in consequence of which it forms acids with time, damaging surface of components. For this reason it is necessary to carry out cleaning of the engine, especially if the machine' has not to be used for a prolonged time.

COUNTER/SHAFT:
The c/shaft does not require any special servicing.

FRAME:
Tighten all bolts and screws of the frame and wheel spokes after the first runs with a new machine. Lubricate with grease the steering head and the front telescopic fork. The sealed bearings of the wheels does not need any greasing. Keep the chains properly tensioned. After every meeting remove the two chains, wash them, and boil them in special graphite chain grease. Keep the twistgrip and cables in good conditions by cleaning them after every race meeting. Also wash out the carburettor and aircleaner (hot soap water) frequently. K&N; type airfilter must be oiled before using. Use only K&N; airfilter oil for maximum performance. Drain the fuel after the closing of the racing season, clean the fuel tank, the cocks and the carburettor to prevent corrosion of aluminium parts due to hydrogenation of old methanol. Regardless of this precaution, it is recommended to inspect this parts at the beginning of the new racing season and to clean them if necessary. The centre part of the frame serving as the oil tank should be cleaned once a year.

CLUTCH:
Replace distorted steel plates and cracked fibre plates new ones. Lubricate the clutch release arm and push-rods with grease. Fibre plates must not be contaminated with grease.

Weslake SOHC Manual, Part 3



Checking the Valve Timing and Ignition Advance, tappet etc; (LEFT) must be done frequently. Read Technical Data Carefully.

After every race meeting it is important, that the Cam Chain clearance is checked (RIGHT). The chain must have a clearance of 5mm between the chain and the Nylon Chain Guide (Cold Engine).

ENGINE TYPE............4 valve pushrod - S.0.H.C. aircooled
single cylinder all alloy engines.
BORE...................85,67 mm.
STROKE.................85,83 mtn.
SWEPT VOLUME...........494,78 cc.(Rebores up to + 0,38 mm
will remain below 500 cc.)
COMPRESSION RATI0......13:1 ยท
MAXIMUM ENGINE OUTPUT..62 B.H.P. aprox. Dependant on spec.
MAXIMUM R.P.M..........8.250
TAPPET CLEARANCE.......inlet .004" - exhaust .006" (cold).
IGNITION...............Rechargeable high voltage Interspan
ignition box.
SPARK PLUG.............NGK type R0 15.
IGNITION ADVANCE.......35 deg.
FUEL TYPE..............Methanol.
OIL TYPE...............CASTROL R-40.
CAMSHAFT TYPE..........83/102 - 85/102.
PRIMARY CHAIN .........RENOLD 1/2" x 5/16" 70 links.
REAR CHAIN.............RENOLD 5/8" x 1/4" 90 links.
S.0.H.C. CHAIN.........RENOLD 3/8" pitch.
FRONT-WHEEL............275 x 23" Nylon hub alloy rim.
REAR-WHEEL... .........350 x 19" Double sided hub alloy
- rim - wheel spoiler.
FRONT FORK.............Suspension 50 mm travel.
WHEEL BASE.............1.325 mm.
GROUND CLEARANCE.......95 mm.
WEIGHT OF MACHINE......82 kg.
MUDGUARDS..............Special fibre-glass (front&rear;).
blue/gold
HANDLEBAR..............Special alloy gold.- 850 mm width.
CLUTCH.................Dry multiplate.
CONTROL CABLES.........Special nylon lined blue.
AIRCLEANER.............K & N cartridge type.
CARBURETTOR............38 mm AMAL concentric, with 34 mm
restrictor.
MAIN JET.. ............620 -680.
NEEDLE.................P 1.
NEEDLE JET.............120.
SLIDE..................No:3.


FLYWHEEL SETTING:


Max. runout on assembled unit 0.002".

End Float -Flywheel assembly 0.025" - 0.040"
Big-end Pin Type & dia. 1.4028
Big-end -Bearing clearance 0.0011" - 0.0017"
Big-end End float 0.012" - 0.022"
Clearance -Main bearings 0.0019"- 0.0025"
Connecting-rod -Steel
Big-end Pin interference - 0.0039" - 0.0048"
Main shaft -interference - 0.0024" - 0.0036"

CYLINDER HEAD:
Combustion chamber volume - 41.23cc
Valve spring fitted length Spring solid length + valve lift + 0.045"
minimum

Valve size - 1 3/8"- 1 5/16"
Tappet clearance - Inlet/exhaust 0.004"/0.006"
Cylinder head Large port - 38mm
Rocker assembly end float 0.010"-0.020"

CAMSHAFT:
Camshaft - Type - 83/102 or 85/102
Camshaft - Angle A.T.C. - 98deg-102deg

PISTON:
Piston - Type - High compression or STD
Piston - Skirt clearance - 0.006" to 0.007"
Piston - Ring gap-top/second - 0.015"

Cylinder liner topped off at - 0.125"-0.127"

To lower compression ratio by half a ratio a plate of 0.31mm
thickness may be fitted under the cylinder barrel.

Compression plate (paper) - 0.010" thickness

EXHAUST PIPE: - 1 7/8" outside dia.
CONTACT BREAKER GAP: - 0.014" to 0.016"
CYLINDER HEAD RETAINING NUTS: - 22 lb/ft. torque.
TIMING GEAR RETAINING NUT: - 25 lb/ft. torque.

AS OUR POLICY IS ONE OF CONTINUOUS DEVELOPMENT AND IMPROVEMENT, THE COMPANY RESERVES THE RIGHT TO CHANGE THIS SPECIFICATION AT ANY TIME.


Weslake SOHC Manual, Part 4

CAM NOMENCLATURE AND VALVE TIMING-WESLAKE MOTOR CYCLE ENGINES:

These notes are issued to give an explanation of the figures used in cam nomenclature, (e.g.86/102/82) and will show how valve timing can be checked to ensure that they are correct for the cam in use.

Fig. 1 shows a valve lift curve for a 86/cam.
The cam dealt with in this explanation is designed for the ramp to be of 9deg. duration, 0.006 inch high at the start of the Polynomial curve, and using 0.006 inch tappet clearance. Hence the valve will be lifted from its seat at 9deg of ramp and will then start to be lifted by the Polynomial curve and will continue for 86deg to reach maximum lift. This now represents the movement of the valve as shown in fig. 1 and explains the "86" designation.

FIG.1* SHOWING HALF VALVE LIFT DURATION AND CAM DEGREES.

For a 86/102/82 cam; the 102 indicates that the peak to peak of the cam lobes when measured at the tappets is 102deg of camshaft rotation by the crankshaft degrees would be 204. The first section of the designation relates to the inlet cam half-period, and the last part the exhaust cam duration. If the cam is shown as 86/102, this implies that the durations of both-cams are identical.

THEREAFTER ALL ANGULAR MEASUREMENT IS AT CRANKSHAFT, THE PREVIOUS FIGURES IN DEGREES MUST BE MULTIPLIED BY 2 WHICH IS THE RATIO BETWEEN CRANKSHAFT AND CAMSHAFT.

FIG.2* SHOWS CRANKSHAFT DEGREES.

When beginning the setting of the valve timing, a crankshaft degree plate must be used. Relating it to the piston at T.D.C. and showing 0 deg with an adjustable pointer is not an easy task. A rod through the spark plug hole is not usually sensitive to be better than 2deg or 3deg, and often much worse. However, it can be found very accurately by making a tool to restrict the piston rising to the top of the stroke by a few degrees. Take an old spark plug body, remove the centre electrode, tap a suitable thread in the hole left, screw in a short threaded rod of a length that will just stop the piston reaching T.D.C. when the plug body is fitted in the cylinder head. It would be advisable to avoid feeling compression during this operation, so cut with a hacksaw a groove down the thread into the plug body. Do not use a plug washer and the air will escape. Fit this body and rotate the crank until the piston contacts the tool. Take degree reading, rotate the crank in the other direction until contact is again felt, take degree reading. A very simple calculation will show the point of T.D.C.

Manufacturers often give opening and closing figures, but because of machining tolerances these figures are seldom accurate, so WESLAKE AND CO LTD prefer to give the point of peak or max lift. This of course is simple to obtain when timing the engine. The second part of the Weslake cam nomenclature is of course the angle between the cam lobes when measured at the tappets.

Now the timing process can be started:
First set the cam in the engine without the crankshaft pinion - this is usually called the half time pinion. Put the piston at T.D.C., and the cam with the lobes farthest from the roller cam followers. Fit the half time pinion and rotate the engine until the valve you are checking begins to open. Take a degree reading. Rotate in the other direction until the same lift is obtained. Go for a set amount, - say 0.025 inch. This amount brings the follower away from the ramp and is always an accurate part of the cam. As the point of max lift that we are looking for is in the centre of the cam, a simple calculation will give this point. If not correct, remove the half time pinion, refit in another keyway and try again. Do not try to find the point of max lift by swinging the crank about this position. The very small range of movement in cam lift over many degrees will undoubtedly cause speculation as to the exact position.
When fitting the dial indicator, ensure that the plunger is parallel with the valve stem and touching the valve spring cap. Use an indicator of 0.5 inch movement.
It is also necessary to ascertain valve to piston clearance at T.D.C. This is normally done after timing, while the dial indicator is still in position. Use a made up lever to fully open the valve at T.D.C., and note the extra movement before the valve contacts the piston. This movement must be equal to or greater than the maker's recommended clearance.

OTHER USEFUL SETTINGS:
For various reasons it is advisable to ensure that the piston top is never less than 0.015" from the top of the bore. Normal tolerance zone is 0.015" to 0.022". Adjust the thickness of the barrel base gaskets to achieve this.
An incorrect adjustment could result in the piston crown hitting the cylinder head.
Measurements are taken between the peripheral "land" of the piston and the upper face of the liner.

VALVE DROP CLEARANCE:

Inlet 0.060" at 7deg BTDC.
Exhaust 0.070" at 7deg ATDC.


Part 5*
The next three chapters show exploded views of the Cylinder Head/Barrel, Crankcase/Timing Cover/Oil Pump and Flywheel/Piston/Timing Gear. Whilst all parts are numbered, I do not have the corresponding Parts Listing, maybe someone out there can supply this for me ?



* Parts 5, 6 and 7 and several images are missing (×)

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