Reports on machines at the 1926 Tourist Trophy Races
The Sunbeam machines for this year are practically standard o.h.v. two-port machines, fitted, however, with larger tanks and larger brakes, two features which are only called for by the special conditions imposed by the race.
Once again it can only be said of the T.T. Sunbeams that they are standard two-port models fitted with 3 gallon tanks and 8-in. brakes, the rear brake now being on the neat side. A new form of hairpin valve spring is used, having coils on both sides of the valves, well away from the stem, really only a double form of the well-known single hairpin type used before. Double pedals are provided for the back brake as usual. The Sunbeam dry sump lubrication system is employed, supplemented by a handlebar controlled pump. Except for engine size and gear ratios, the 350 c.c. and 500 c.c. machines are identical.
Reports on sports machines of 1927 (penned in 1949)
In October Motor Sport contented itself with "tearing off some strips" about a variety of machines that constituted its stable, but in November returned to its test-reports, trying a Model 90 Sunbeam. This 493-c.c. solo offered complete controllability, with low, comfortable saddle and compact build for its considerable weight. The machine tested was actually a reserve T.T. job, so that some intractability could be explained away by quoting compression and bottom-gear ratios, about 7-to-1 and 8-to-1, respectively. Moreover, it was reported that "further embarrassment was a twist-grip control, a method we had hitherto never tried"!
However, through London from Euston Station the Sunbeam wasn't too tricky and down the first available by-pass road it came into its own, piston slap vanishing at over 55 to 60 m.p.h., and half-throttle producing a gentle 70 m.p.h., the bicycle rock-steady. Later, acceleration from 70 m.p.h. onwards was found to be terrific and very soon some 85 m.p.h. was attained, when the Sunbeam shot on to a rough patch of road. Damper and shock absorbers had not been tightened, causing the machine to rock and pitch so that the rider lost the footrests, but never for a moment did the Sunbeam go out of control, or start to wobble. Later still, speeding cross-country in the thick mud and fallen leaves of autumn, never a trace of a skid was provoked. Incidentally, steering damper and shock-absorbers could be adjusted from the saddle, the former with one finger.
At Brooklands rain spoilt the test, but the Test Hill was ascended so fast that the summit was crossed air-borne at 40 m.p.h., after changing from bottom to middle crossing the line at the foot of the Hill. On the outer-circuit the engine was happier at 70 to 80 m.p.h. than at 15 or 20, and the maximum was estimated at an easy 90 m.p.h.
The front brake was the most efficient ever met, milled wheels provided instant adjustment of both brakes, the finish of the machine was superlative and the twin silencers gave a pleasant, very deep, mellow note. Interesting features were "grasshopper" valve springs, dry-sump lubrication, with an auxiliary pump actuated by a handlebar lever, and, on the production job, a front-wheel stand. Snags were confined to heavy fuel consumption and poor slow running from the T.T.-tuned engine, offset by negligible oil consumption, and breakage of a shock-absorber bolt and the float-chamber fuel-line nipple. Very high marks, then, for the Model 90. It cost 100 gns. with 1928 improvements.
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