(Tech Sheets courtesy of Geoff
Coglan)
Geoff Coglan contacted us to mention that he possessed a small collection of race motors, one of which was an MSM DOHC Magnum motor, Eng No. MSM D0023. This engine has coil ignition instead of Magneto, and fortunately for us, Geoff also has the instruction and specifications sheets for this engine.
It was purchased in the mid 1970's by Trevor Anderson of Bundaberg, Qld Australia, and was raced in a formula 500. Sadly it was prone to piston failure, half time pinion gear and idler gear failure. Trevor did not have much success with this engine and shelved it until about 10 years ago, when he showed it to Geoff who was impressed with the look of it, so much so that Geoff was presented with it. Since that time, Geoff has had a new half time pinion and idler gears made for it, and has plans to fit it to a frame for clubman style.
Geoff has passed on copies of the sheets which sadly have deteriorated through time (and some scribbled notes) and a few details have had to be omitted. We therefore suggest, as with all technical information on these pages, that they be treated as information only.
Bore/Stroke: 85mm x 88mm.
Capacity: 498cc.
Compress Ratio: 14:1
Carburettor: 36mm AMAL
Ignition: Magneto SR I
RPM: 8,300. (Work rpm 7,800)
Oil Pump: Double acting Plunger
Fuel: Methanol
Valve Arrangement: Inclined 30 deg with cam acting over Valves on cam follower buckets.
Tappet Clearance:Inlet .006" Exh. .008"
Valve seat Angles: 45deg
Valve Spring Comp: Valve on Seat 140lb
Full Lift: 240lb
Valve Spring Free Length: 1.90" (Written over original figure.)
Valve Spring Length with Valve On Seat: 1.50" (Written over original figure.)
Gudgeon Pin: .75"
Piston Rings: 3RD .130" x .062"
Piston: Full Skirt
Carb Main Jet: .650" - .698"
Needle Jet: .120"
Slide: No. 5
Exhaust Pipe Length: 52"
Lub Oil: Castrol R40 Golden Fleece C.B.M Do Not Use Mineral Oils
Oil System: Reciprocating Oil Flow
Oil Tank Level: In Line with approx. Cylinder base at bottom of Oil Tank
Oil Qty: Half Gallon
Oil Return: To top of tank into free space
Oil Feed Pipes: 1/4"
Spark Plug: R49 (N5 Champion for Cold conditions)
Engine Mount in Frame: Vertical (mounted on rubber mounts Only in cars)
Timing chain Tension: Firm
Cylinder Head tension: 40' lbs (in 10lb increments)
To Strip Engine
Remove front Timing Cover, be careful not to lose 3/16" washers and springs behind them on cam shaft oil feed quills. By removing timing cover away, carefully and equally, the oil feed quills can be observed through the top. Slacken mag and move towards cylinder to slacken chain. Slacken grub screws in centre of Cylinder head on cam shaft chain tensioner, and with a key on camshaft centre stud, turn the tension shaft clockwise.
Remove the two 3/16" top screws, holding the top of cam bearing cup to the top cover. If the covers are firm, rap them gently under their edge with a wooden drift to release. The two cams can be observed now in a vertical position. Hold each cam lobe with the jaws of a suitable shifting wrench, slacken the two main nuts on the drive end. Remove the front timing screws, two in each cam sprocket, now ease off one sprocket at a time over the end shaft with the chain slackened and allow the chain to hang.
Slacken the adjuster screw on the rear of the cylinder at the bottom by unlocking the two inside lock nuts. Keep screwing the outside screw outwards. Of course the two top and bottom screws on the adjuster must be removed so the slide can slide towards the mag. Once this is done the mag can be removed completely with the mag sprocket, leaving the chain inside.
Remove the stud in the centre of the top idler gear so that the vertical chain runs over, pull the sprocket off its spindle, this releases the top and bottom chains at once.
Remove the pump cover, remove the pump, slacken the pump crank nut on the spindle, remove the timing chest cover by holding the thumb against the spindle driving the pump so as to leave the driving gear inside, release the main shaft spindle nut and extract the half time pinion gear. Then by gently feeding the chain through the slot at the top, the timing gear sprocket can be taken out below with the chain.
Release the cylinder head bolts at the top, each a turn at a time until they are free, remove the cylinder head. The cylinder head can be lifted now being careful not to let the piston fall and damage it.
To split the crank cases, wrap a chain around the drive sprocket and anchor it firmly to the engine bed, slacken the main nut a few turns, remove the circlip and sprocket and with a Litchfield three leg puller, with the leg hooks behind the sprocket carrier, the puller centre screwed up un the shaft centre, extract the chain sprocket carrier spline off its taper. There will be considerable tension required on the puller to extract the splined carrier. It's wise to leave the drive nut in place in a slackened position to avoid injury to the mechanic when the sprocket carrier lets go from its taper on the shaft. Remove the Key, and then the crankcases can be rapped apart with a wooden drift to expose the crankshaft assembly.
When the drive shaft wheel is pressed off the crank pin with the conrod installed with its bearing, it will be found that there is a fine scribe sign across both wheels opposite T.D.C. With an accurate steel square these two lines can be brought into absolute alignment, as the drive shaft wheel is pressed a short distance onto the crankpin.
When the assembly has been pressed together completely with a 4lb copper hammer a sharp rap on the rim of a solid section of the drive shaft wheel will bring the two lines into alignment, if they have not remained aligned during the pressing operation. A check can be made on the alignment, finally by installing the flywheel in the crankcase, holding the crank cases firmly to the bench, a dial indicator on the surface of either shaft till a maximum of .001" to .002" accuracy is obtained. The run out on the flywheel side cannot vary a great deal because of the accurate shoulders on the crankpin itself, holding them in alignment under pressure.
Maximum vertical play in the crank pin shoulder should not exceed .002" and the conrod sleeve when replaced in the big end assembly should be hound to a neat +/- 0. The crankpin should never be reground or spun and hand ground with emery paper, when a new bearing is being fitted these crank pins are ground to 42mm on the bearing surface by 20mm +.015" for side thrust clearance of the conrod, the bearing sleeve once pressed into the conrod has an allowable honing clearance of -.002" ID, to ensure a perfect roundness of the outer sleeve. Reassembly of the engine is a reverse of the strip down procedure excepting.
TO TIME THE CAMS
Install all chains, adjust bottom chain tension to 'firm' adjust cam chain to 'firm' with main cam nuts tightened to finger tight against the cam sprockets. Install timing chart on the drive side. Rotate the engine from absolute T.D.C. to 80o A.T.D.C. fit the two 3/16"set screws and secure the cam drive sprockets to the EX cam (do not tighten the main nut accept finger tight against the sprocket at this stage ] rotate the engine forward and indicate valve lift, .005"at 80 o A.T.D.C.adjust negative and positive to this timing of the exhaust cam. First only secure the two 3/16" lock screws and hold the cam lobe at verticals in dismantling and lock main nut {CAUTION DO NOT OVER TIGHTEN THIS NUT ]it serves no purpose except to retain the shaft against the bearing thrust, and over tightening could snap the thread off the shaft.
Rotate the engine forward , the exhaust valve should close between 42deg and 46deg A.T.D.C. At this stage rotate the engine backwards to about 80 o B.T.D.C. then come forward again to 68o B.T.D.C. rotate the inlet cam anti-clockwise against the follower, as with the exhaust cam then fit the two 3/16 "timing set screws , screw the main nut up to finger tight and rotate the engine forwards again , indicate as before with the exhaust valve till the inlet valve registers .005" off its seat, make adjustments accordingly till the inlet valve opens 65deg B.T.D.C. prior to the exhaust valve closing at T.D.C.
Timing the engine in this way, puts full load on the timing train and ensures and ensures all slackness is taken up at valve lift when with seeing that the whole of the timing chain configuration is exposed, then any slackness developed in the chains can be observed which should be no more than a small relief of tension, only on the slack run of the chains.
The ignition timing is a simple procedure, the mag sprocket should have been extracted from its taper from a suitable puller prior to installation on the motor, with the mag timing chain running on the sprocket. Move the mag outward until the chain tension is just firm, secure the mag block studs in their slots. Bring the engine to 10deg B.T.D.C. on the comp stroke, rotate the magneto block clock wise on the contact and, till the contacts are barely breaking, gently tighten the lock nut, rotate the engine backwards to about 70deg B.T.D.C. move forwards and check the mag timing. Cover the timing cover top and bottom, service with rubber gasket compound tighten securely making sure that oil quills to cam shaft with springs and washers are fitted securely. DO NOT UNDO THE EXTERNAL NUTS AND BANJO COUPLINGS TO THE CAM SHAFT AS THE COVER AND THE PIPES CAN BE REMOVED AS A UNIT AND ALL ALIGNMENTS WILL BE RETAINED.
I.O 68deg B.T.D.C.
I.C 78deg A.B.D.C.
E.O 80deg A.T.D.C.
E.C 45deg A.T.D.C.
IGN 40deg B.T.D.C.
When fitting the gasket 1/8" "O" Ring, place in groove leaving surplus protrude timing face. When fitting Cylinder head, hold the blade over gasket seal to retain shape in groove, tighten cylinder head and remove blade, allow cylinder head to retain compress gasket when tensioning down.
If the cam follower bucket shows signs of wear they can be refaced to a depth of .0012" with safety.
Each engine comes with a set of cam buckets, etched on their sides is the particular valve they belong to, i.e. Ex or In. Replacement buckets are always available, when ordering measure the head thickness of the bucket replacements will be supplied to either suit that engine with a clearance ground, or an extra head thickness of up to .060" in .010" increments. It is advisable to grind away the head of the cam follower bucket to achieve tappet clearance, anyway it is advisable to have the cam follower bucket heads reground on a wet stone.
When ordering valves for your engine, always state clearly the length of the valve from the flat surface of the valve head to the top of the collet groove to ensure the valve comes the correct length to suit your model. The valve stem length is very critical each engine can vary in this manner as much as .080" from valve to valve. This was necessary to ensure absolute correctness of all settings to specifications for the Magnum Engine.
Finally, remember that .002" extra or less tappet clearance will alter the cam timing considerably, so it is imperative that when this work is carried out, absolute care must be taken. All bearings fitted to the cam shafts are a free fit on the shaft, to eliminate the necessity to hammer the cam shafts free of their bearings. Bearing replacements in this department should be very rare anyhow, For that matter, the entire bearing assemblies throughout the engine have been amply catered for and should give very long service indeed, with the right care and attention to this fine product.
PLEASE NOTE
The Magnum engine and its upkeep rests strictly with the owner.
There is no guarantee with the engine of any kind in part or as a whole Unit.
There is no Service department at this factory and the engine will not be accepted for service of any kind.
Spare parts are available at this stage direct from this factory, until a reliable distributor in this country has been appointed.
At all times, technical advice is available from the manufacturer to any person whether they be an owner of an engine or not.
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