SPORTING MACHINES ON TEST.
The 31 h.p. Longstroke “SUNBEAM.”
By ARNOLD RADCLYFFE.
N the general opinion of motor cycle savants, the 493 c.c. overhead valve ” Sunbeam ” is the ideal production of Sunbeamland, but as a very able description of the latter model has appeared already in the motoring press, I decided to make a test of the 31 h.p. longstroke machine, especially as this is catalogued as “The Speedman’s Machine,” and should therefore be of interest to our readers.
It was my original intention to enter the Sunbeam for the Southern Scott Scramble, but as the date of delivery was uncertain, I had to be content with going over the course on the occasion of that event in an unofficial capacity.
When undertaking a trip of this kind, one is well advised to be quite familiar with the control and habits of the machine to be used ; but I found this precaution entirely unnecessary with the Sunbeam, as it seems to fit everywhere directly one takes to the saddle.
First Impressions. My first impression of the machine was that it seemed to occupy no room on the road, the all-black enamel and
inconspicuous finish of the tank making the bike look much smaller than it really is. The design permits of an upright riding position when cornering, and yet allows a crouch for track work, without having to extend the elbows too far forward. The throttle and magneto controls are placed’ conveniently, the former opening inwards, which I prefer. Mounted forward at the right hand side of the tank, the gear lever is very conveniently situated for a quick change, but I was inclined to foul my knee against it at times. This, of course, would be obviated by using knee grips of the ” Dance ” pattern. On threading my way out of London, I discovered some of the sterling qualities of the Sunbeam, which include a sweet clutch and rapid acceleration.
At first I had a little trouble with a carburettor “flat spot” when picking up, which caused the engine to stall on several occasions. The defect could not be traced to any stoppage in the carburettor, and continued until I replaced the 38 jet by a 41, upon which the objection disappeared.
Testing on the Great West Road.
Before putting the Sunbeam at a short speed test on the excellent surface of the Great West Road, I tried the suspension on an adjacent stretch, which has not been touched for generations by the hand of man. Some idea of the surface at this point may be gathered, when I mention that two well sprung touring cars travelled over it very gingerly at about ro m.p.h. Thanks to the design of the forks, however, and the addition of D. & B. stabilisers on either side of them, the Sunbeam took the rough surface at a good speed, with a complete absence of front wheel bounce.
Once again on the main road, the machine showed its paces, which were quite up to expectations, if not rather beyond them. I may mention that this particular machine had been well run in, having in fact two recent Golds to its credit, so that my criticism was in no way hampered by the irritating ” newness ” usually to be taken into account on such tests.
Comments on Coursing Camberley. Having thus established friendly relations with the Sunbeam, we proceeded together to Camberley to see how we should shape on a test of more than average severity. The route was unfamiliar to me and from the condition of the majority of machines on finishing the first round in the morning, I concluded that high footrests were essential, and silencers in front of the engines were likely to be carried away. Now, the Longstroke ” Sunbeam ” is very nicely silenced, only a pleasant
SPORTING MACHINES ON TEST—continued.
note being heard when the silencer in front of the engine has dealt with the gases ; and, in addition, the footrests are more or less normal. I noted with relief, however, that the foot brake is mounted separately from the footrest, and when I bent the left rest during the run, the brake was not put out of action. In point of fact, the Sunbeam expanding front brake is the best I have tried so far and it is possible to stop the machine in its tracks either with this or the other brake. As good braking is never more wanted for cornering on the course of the “Scramble “—with the possible exception of the T.T.—it helped me to maintain a fast average without risk of smashing the machine. It was possible to come right up to a hairpin bend at full throttle, shut off suddenly and apply both brakes hard, then aided by the ability of the machine to corner at a good angle, to get away quickly again without skidding.
For such a course as the Camberley Club organisers select for the entertainment of their members and guests, I found the Sunbeam ideal ; the short wheelbase, the good acceleration and braking, combined with the perfect, absolutely perfect steering and shock absorbing front forks, all go to make the machine most manageable over a track, which is full of surprises in the way of gullies, quagmires, pot-holes and soft sand. The latter is liable to strike terror into the heart of the most hardened competition rider, when it is encountered suddenly at speed.
The Sunbeam Acquits itself Nobly. I am glad to say, the Sunbeam completed the course without throwing me out of the saddle and that Wild and
Woolly, Red Road and the Devil’s Drop were negotiated without any faltering and practically without wheel spin. The latter I attributed to the new Dunlop square studded tyres, which besides adding to the stability of the machine assisted materially in the braking effect, for which the Sunbeam is so remarkable.
During my trip round the course, I noticed the front forks bottomed several times on unseen pot-holes, and I was anxious about the steering head, but no flaw was discoverable at the finish. Needless to say, the springs are quite stout enough for ordinary work and are, in fact, larger in diameter than those of last year’s model, but as the pot-holes were something in the nature of hidden elephant traps, it was surprising that the steering head was intact at the finish. Apart from the slight bending of the footrest, caused no doubt by an impact with a concealed stump, the
Sunbeam came through the test surprisingly well and in spite of the fact that top gear could seldom be engaged, the engine kept very cool and showed no signs of tiring. I gave her plenty of oil by means of the auxiliary hand pump and though the mechanical pump was delivering oil freely through the sight feed, the engine could not be prevailed upon to smoke. One hardly expected clouds of smoke, however, as I found it possible to stand on the kick starter almost indefinitely against compression.
Technical Comments. The magneto fitted is an B.I.C. square type situated behind the engine, high up and sheltered by the cylinder, the instrument giving a good spark at all speeds and (Please note, 0! King of Thessaly) starting was a matter
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