HINTS ON THE TUNING AND MAINTENANCE OF THE P. & M. PANTHER
“1”°A0-^#’Ned’Ar-P•-^Are.A.e-Pskro’dVs”.’Vsl HINTS ON THE TUNING AND MAINTENANCE OF THE P. & M. PANTHER.
By C. T. ASHBY & F. C. TOWNSHEND.
IT is a commonly accepted fact that the P. & M. range of machines are all exceptionally well made, limits
of error in machining all parts being probably the smallest allowed in the Trade. For this reason they require and deserve gentle handling during the first few hundred miles. The oil supply must be liberal—controlled by the milled disc on the top of the timing case— and the sump should be drained and cleaned (together with the filter) after the first 100 and 300 miles. After this it need only be done about every 800-1,000 miles The filter is attached to the oval disc bolted to the bottom of the near side of the sump, and when replacing, a little jointing compound, such as ” Herrnatite,” should be smeared on the flange faces and washer to prevent oil leakage. After 500 miles or so it will be found that sufficient oil for normal solo touring work will be delivered with the oil regulator turned right to the ” e” position. (This regulator has a total movement of a quarter of a turn from full off to full on, and is so arranged that the oil cannot be turned completely off.) It is easily accessible when riding, and when indulging in a scrap or a lengthy ” blind” it is imperative to turn more oil on.
To cope with the excess oil in the machine’s early life, a plug is fitted that will stand a lot of oil, but not a great deal of heat, and it will probably be found advisable after the running in period to fit a plug that will stand more heat, but remember that the more heat a plug can cope with the less oil it will stand. The following list of K.L.G. plugs progress in order of ability to stand heat :—G.1 ; 230; H.S.1 ; H.S.3 ; 244; F.12 ; 268; 180.
The T.T. Panther requires a hotter plug than the Standard, the H.S. l and H.S.3 being those suggested for Standard and T.T. respectively, one grade hotter in each case being used for sidecar work. The lubrication system is fool-proof and capable of coping with all conditions, except that for long distance Brooklands races and T.T. work it is advisable to fit a small extra tank and hand controlled pump on the saddle down tube to supplement the existing supply and keep the sump replenished. The best place to insert this extra supply is on the centre line of the crank-case, between the base of the cylinder and the magneto ; and close to the magneto as possible in order to miss the oil channel
cast in the crank-case for the main oil supply from pump to cylinder.
To carry out ” a top overhaul” it is riot necessary to remove the engine from the frame, nor to disconnect the front driving chain, chain guard or rear-brake. Place suitable packing under the front of the sump, and remove the H.T. lead, exhaust pipe, valve lifter wire, carburettor and top main engine bolt and cones, and slide the telescopic tube enclosing the push:rods upwards until the bottom ends of the push-rods are disclosed. The four nuts on the top ends of the long rods passing right through the engine, and two more between the cylinder pins should then be taken off, and the long rods knocked downwards, releasing, step by step the frame lugs, distance collars, rocker-box complete with pushrods and telescopic tube, cylinder head, and cylinder. The necessary work can then be done on these items, reassembling them in exactly the reverse order, knocking the long rods upwards, step by step, as each item goes into place. Prior to 1926 a copper asbestos gasket was fitted between cylinder and head, and the two extra nuts between the cylinder pins were not used. Valve clearances should be maintained at 3 and 4 thousandths, inlet and exhaust, respectively, the tappets being adjustable to accomplish this.
When serious work has to be done on the engine it is better to remove it complete from the frame and place it on the bench. Work is much faeilitated if you have a vice big enough, when the engine complete may be gripped in the vice by its sump, approximately in its normal position. When removing engine leave the foot-rests on—they are useful for man-handling it. The bottom end of the engine unit is held in the frame by a bolt and a pair of cones, similar to the top end (standard engined and when all controls etc, front chain, chain guard and rear brake rod have been detached, the whole unit can be dropped out complete on removal of the cones at top and bottom.
This needs practically no attention except to ensure its proper lubrication, and correct re-adjustment of the operating rod after moving the box to adjust driving chain tension. As to the former, good engine oil (Castrol XI, or R) should be used, the filling hole functioning as a level indicator. As regards adjustment of the operating rod, above the filling plug is another hexagon
headed plug containing a spring loaded plunger. This latter engages in countersunk holes in the face of an internal operating wheel, each hole corresponding to a gear position (there is not one for neutral) and when the gear lever is in any notch in the quadrant on the tank, the corresponding countersunk hole should be seen dead central through the hole in the gear-box cover from which the spring -loaded plunger and socket have been removed. Lengthening or shortening, the vertical operating rod as required will effect the necessary adjustment. Should it be required to dismantle the gear-box completely, a request should be sent to Messrs. Phelon & Moore, Ltd., of Cleckheaton, Yorks, or of 77, Mortimer Street, London, W.1., for a copy of” The Book of the P. & M.” which will be published shortly as this deals more completely with this and kindred details than is possible within the confines of this article. After dismantling the P. &M. gear-box it is a bounden recessity to re-time it correctly when reassembling, otherwise trouble will ensue, and this job usually requires the guidance that is obtainable from the above book.
A Sturmey-Archer clutch is fitted, adjustment in the operation of which is found at the lower end of the operating lever mounted on the gear-box cover in the form of a hardened screw and lock-nut. Care should be taken to keep this adjustment up to scratch, as any excess of wasted travel of the hand lever will cause difficult gear changing due to drag in the clutch. It is not possible to give a full treatise here on care and maintenance of all the various parts of the machine, but the following hints may help to maintain your engine in top form. There is no short cut to speed, and although the T.T. Panther is basically a fast engine, careful working on it will be productive of more” horses” and hence more speed. It is mainly, however, a matter of spotless cleanliness and the elimination of friction of moving parts and of gas. The engine should be completely dismantled down to ” splitting” the crank-case, examining each part as it is removed for signs of high spots or uneven wear, and if such should show up they must be dealt with before reassembling. There are four points to be mentioned here :
(1) Mark the piston so that you may replace it the same way round.
(2) There is a narrow washer behind the cam levers, between them and the crank-case–do not forget it when reassembling.
(3) The driving sprocket must be removed before splitting the crank-case–this is on a tapered shaft and has no key.
(4) The main timing pinion must be removed from the other end of the crank shaft–this is a driving fit on a parallel shaft and has a key, and some form of ” drawer” must be improvised to remove it. (N.B.-1927 T.T. engines have a hollow shaft this side, and care must be exercised when removing this pinion not to damage the end. All parts must be very carefully cleaned, and dried with a clean rag that is not fluffy, and bearings washed out, examined, and re-lubricated. The cams can with advantage be smoothed with a carborundum ” slip” (of the finest grade you can get) as also the pads on the
cam levers. High spots on tappets and any other steel working parts can be dealt with in the same manner. High spots in the piston should be tackled with a polishing mop—emery should be avoided here as particles get embedded in the aluminium. When the rings are removed, keep them in sequence so that they may be refitted in the same order. For racing, the following piston clearances should be secured :—Above the top ring, 30 thousandths of an inch ; between the rings 24 thousandths ; under bottom ring (not the scraper ring at the skirt) 14 thousandths, tapering to 10 thousandths at the skirt. If your piston has a scraper ring fitted, leave this off for speed work. The cylinder bore is 84 m.m. precisely, so that the micrometer readings to give the above clearances will be 84mrn., minus 30 thou. inch, 24 thou. inch, 14 thou. inch., and 10 thou. inch respectively. To obtain these clearances if the piston has to be reduced is an expert’s job, and should only be entrusted to a thoroughly reliable man. The cylinder should be lapped out using first the finest flour of emery you can obtain, followed by crocus
powder, mixing both with clean oil, and finally liquid metal polish. Obtain an old piston and rings for this and mount it by its gudgeon pin on an old connecting rod or a length of hard wood. On no account use your working piston. Time spent on this will be well repaid, for the cylinder is the point of highest frictional loss owing to the tremendous distance travelled by the piston in even a minute at high revs., coupled with very extensive side thrusts through connecting rod angularity
Rings should be tested in their grooves for freedom in the piston, and should then be placed square in the cylinder to test gap clearance. This should be 5 to 6 thousandths.
Valves must be cleaned and polished, and much time may be profitably spent in polishing the head and ports, starting with medium emery, using gradually finer and finer grades until you feel you have got sufficient polish. The smoother your ports, exhaust pipe, and carburettor throat are, the more gas you will get into the cylinder and the more complete will the scavenging be. After polishing the head, grind in the valves carefully and completely, at the same time checking valve guide clearances. If the valves are ” sloppy ” in the guides, the latter should be punched out and new ones fitted. When re-fitting valves, smear the stems, with graphite grease, and see that the split cones are properly bedded home.
Stronger valve springs are obtainable from the factory but these are unnecessary for any but racing work. Examine the rocker box and rockers, and if there is play in the rocker bearings it is best to send the box complete to the factory to be re-faced and the rockers re-fitted.
Do not start to erect until all parts are absolutely ready, and do not forget that cleanliness—real and not half-hearted–is 25 per cent. of the battle. Handle all parts gently and do not drop them on hard floors or allow them to knock together. The consequent scars, often invisible to the naked eye, mean extra frictional losses, and thus less power available at the driving sprocket.
Points when Re-Assembling.
The two halves of the crank-case must go together so that the face on to which the cylinder beds down is perfectly flat, and the joint faces should be smeared with a little Hermatite jointing compound. The flywheels should revolve in the crank-case with absolute freedom.
No jointing compound should be used for the joint between cylinder and crank-case, but a little must be used for the joint between cylinder and head.
A box spanner is useful for driving the small timing pinion on to the shaft, taking care that the key remains in its keyway. All the timing wheels are marked, and so no difficulty should present itself here. Vale timing should be approximately :—
Exh. opens 50° before B.D.C.
„ closes 18° after T.D.C.
Inlet opens 12° before T.D.C.
closes 48° after B.D.C.
Mag. timing : fully advanced points breaking 50° to 55° before T.D.C. Valve clearances :—
Exhaust 4/000 in. cold. Inlet 3/1000in „
Re-check these after the engine has been replaced in the frame.
During assembly, use the oil-can liberally on all moving parts, using the same oil that you are going to run on.
As to carburation, this is usually a matter of personal taste, and for speed work one cannot be better guided than by general racing results. In general, however, irrespective of make, a slightly larger jet is required than for ordinary touring work.
A high compression piston for use with alcohol fuel (P.M.S. II) is available from the works, but if this is used, full strength valve and return springs must be fitted.
Finally, as much speed comes from the elimination of friction, do not forget wheel bearings, chains, gear-box bearings, etc., and that too much oil is almost as had as too little, owing to its clogging effect, especially in the gear-box.
The Panther engine likes revs., and it is often possible to gain a mile or two per hour by slightly dropping the gear ratio. Fitting an 18 tooth instead of a 19 tooth on the engine shaft drops the top gear ratio from 4.5-1 to 4.75-1. The most suitable ratio, however, depends entirely on circumstances–nature of road-surfa.ce, wind direction, gradient, lengths of race, etc.
In all cases information will be gladly given by the works or their London office in response to any enquiry.