A two-stroke twin in a world of four-stroke singles and the first bike to boast a kickstart—no wonder Alfred Scott’s creation was in the news. Here’s a Motor Cycle roadtest, followed by a rider’s impressions of his Scott and a reader’s letter about its fuel consumption.
EVER SINCE THE two-stroke Scott motor bicycle carried all before it in the Coventry Motor Club’s hillclimb of 1908 we have longed for a lengthy trial of this fascinating machine. It was rather a tall order to endeavour to embody all motor cyclists’ ideals in one machine, yet that was the ambition of Mr Alfred A Scott when he designed his two-stroke, two-cylinder, two-speed motor bicycle.
It so happened that on the occasion of our first trial of this machine the roads were thick in mud, and although the stability of the machine left nothing to be desired, we must candidly confess we were not altogether happy. The speed of the engine surprised us—3,000rpm was nothing to it—and consequently we found it more difficult to control at slow speeds than a four-stroke-engined mount. This, however, was almost entirely due to our inexperience with the Scott, for, since we have become accustomed to the manipulation of the half-compression lever (on the left handle-bar), the spark and throttle levers (right handlebar), and the change-speed pedal (on the right footboard), we have developed a great liking for the machine, and are quite at home with it in thick traffic or on winding roads.
As regards its running, it may be compared to four-cylinder machines, the two-cylinder two-stroke engine being equivalent in torque to the four-cylinder four-stroke type. This is saying a great deal, for everyone knows there is only a negligible amount of vibration with four-cylinder engines. This even impulse of the two-stroke Scott motor accounts in a great measure for the longevity of the tyres and the success of the chain transmission. Never have we experienced such comfort from a positive method of transmission, and, what is more, the Reynold chains have never given a moment’s trouble, and have only required shortening once in 700 miles. In fact, the machine as a whole has proved wonderfully reliable, our one and only contretemps being the result of misfortune more
than anything else. It was in connection with the carburetter. The high-speed driving chain is immediately under the float chamber, and the chain having developed a certain amount of slackness, gradually chafed a tiny hole in the carburetter casting and caused a leakage before the trouble was found out and rectified by adjusting the chains.
The original method of starting the Scott engine is a great success. One has merely to inject a small quantity of petrol into the transfer ports, flood the carburetter, and with a smart rearward dig of the foot whilst seated in the saddle, the engine is humming merrily. The acceleration powers of the engine are truly wonderful considering its size–2⅝in bore by 2½in stroke [445cc]. It takes up the drive from a standstill without the slightest hesitancy, and the high gear can be engaged after thirty or forty yards. Knocking is unknown with this engine and, what is more, the unique system of constant thrust is obtained under all normal conditions, so that slackness in any of the bearings has no effect in causing clanking or noise.
We have nothing but praise for the two-speed gear. It has received no attention whatever at our hands, but its utility is undoubted. All parts are made from mild steel pressings and stampings, and every wearing part is case hardened and ground to limit gauge to obviate wear. A system of central drive is adopted. On either side of the flywheel is mounted a sprocket, driving on to a counter-shaft in which the change-speed gear is incorporated. The gear consists of two metal-to-metal expanding ring clutches, and by the rocking motion of the gear pedal either gear may be engaged, the horizontal position giving a free engine. The final drive to the rear wheel is by a single chain.
The low gear enabled a clean ascent of Warmington on the Edge Hills, with the roads exceptionally heavy, and there was plenty of power in hand. Hills such as Bunny, near Nottingham, it takes in its stride. The writer had made a non-stop ride from Newark (25 miles) well up to legal limit, but if the designer had seen the way the Scott roared over Bunny when the throttle was opened it would have done his heart good. For speed on the level the Scott can easily hold its own with the best 3½hp machines of orthodox type.
There are many special features embodied in the design, some of which we may refer to briefly. The open frame, for instance, is very convenient, and enables the rider to wear a long thick motor coat enveloping the knees and legs. In the colder months we found this an untold blessing. The spring footboards are also good, and entirely do away with that stiffness one notices after riding a long distance with the legs in one position. The water-cooling apparatus has been well thought out, the spring forks are very effective–albeit they develop a certain amount of rattle when the rollers are worn—and the crankcase inspection covers are useful to enable one to ascertain the amount of oil in the base and the condition of the big-end bearings.
The Bosch magneto is located above the countershaft gear and driven by means of a chain. Some time ago a contributor to these columns pointed out that this indirect drive of the magneto may cause trouble by a variation of the timing owing to chain stretch. We find that the very slight variation which can take place from this cause is easily rectified by the position of the ignition lever on the handle-bar. By the way, the Scott engine has the ignition set much further advanced than the usual four-stroke engine, for the spark should take place (with ignition retarded) exactly at the top of the stroke.
One or two readers have at times queried us as to what would happen in case of a backfire into the crank case with a two-stroke engine. Speaking from experience with the Scott, we have noticed that the crankcase covers tremor visibly—that is all. Backfiring is due to burnt-out gauzes in the transfer ports.
From our experience the following minor points might receive attention: the oil pump is somewhat inaccessible, as also the auxiliary air lever. It may, however, be mentioned in connection with the latter that, once set, it is right for the remainder of the run, unless exceptionally steep gradients are encountered. The spring stand fastener is hardly secure enough. We should also like the change-speed and brake pedals placed further forward.
To sum up, there are very few points open to criticism on the Scott motor bicycle; the engine certainly cannot be coaxed to run as slowly as the four-stroke type, and the petrol consumption is much higher—about 50mpg—but against these disadvantages one has the simplicity of the two-stroke motor writ large on the memory, and a machine that can run as smoothly and do what the Scott can without valve gear, cams, and poppet valves is a competitor to be reckoned with.
This Scott rider was clearly more than satisfied with his mount…
FOR EASE OF starting, one must go far to find an easier. A little petrol is injected through the spring nipples on the side of each cylinder, at any rate in cold weather, and then, while seated on the saddle, a smart push with the instep of the right foot on the starting crank, which is permanently attached to the back hub, and the engine starts. You close the handle-bar controlled throttle a little when the engine is running well, a matter of a few seconds. Then, with your left foot on the ground, press the low gear pedal gently with the right heel, and off you go smoothly without jar. Bv adjustment of throttle and extra air lever you can run at about eight miles an hour on the low gear, and by closing the extra air and cutting the magneto in and out with the handle-bar lever, you can crawl behind cattle or traffic, as I frequently have to do on market days.
When the rider is ready to go faster, the high gear pedal is pressed forwards and downwards, as smartly as you like, and the hum, which on the low gear sounds loud and of a high tone, changes to a low, quiet note. In fact, when the mixture is correct, the rider can really only hear the swish of the chains.
If you want to run up to a point and stop, you cut out your magneto, put your gear pedal into the horizontal free engine position, and apply vour handle-bar brake. If you want to pull up short, you go through the same process, but put on the shoe brake in the back sprocket wheel, which is operated by a pedal placed conveniently near the left heel. This will pull the machine up and stop the engine, but the jar must necessarilv be a strain on the engine, so unless there is urgent need it is always better before stopping to put the gear pedal in the free position.
The spring forks are excellent, but the rollers must be kept oiled, or they squeak. There is practically no engine vibration, as the explosions follow each other so rapidly as to be indistinguishable, merely merging into a continuous hum. It is a wonderfully clean machine to ride, as the undershield keeps all dirt off, and the tank, being slanted below the saddle, keeps any oil from the gear chains from flying about.
The lubricating oil is carried in the two main down tubes and injected by a hand pump placed near to the junction of seat and down tubes. This is no trouble when the oil is warmed and thinned by the heat of the engine, but when oil is cold, as in frosty weather, it is a hard job. I wish the makers could see their way clear so to make the pump that the handle pulled up towards the rider instead of away from him, as it does now.
It is a great boon to be able to see the actual level of the oil in either crank case in about fifteen seconds by simply undoing a wing nut, and also to be able to verify that one’s oil pump is working, as with the crank case open one can watch the level of the oil rise when the pump is operated. The carburetter seems most efficient, and the ease with which the jet can be removed, cleaned, or changed is very nice. To remove the carburetter entirely is more of an operation, but when one has done it once it becomes quite an easy matter.
The tank holds plenty of petrol for at least 100 miles, and is fitted with a large filling orifice and strainer. The magneto is excellently placed out of harm’s way behind the tank, and is driven by a chain. I suppose that in time the, chain will stretch enough to make a readjustment of the ignition necessary, but I have not required to meddle with it so far, and when I do the makers’ instructions are so clear that I foresee no difficulty.
No maohine is perfect yet, and as a non-expert amateur, if I were asked to improve on the Scott, I should ask for a more easily worked oil pump, or, better still an automatic lubricator, extra air lever to be handle-bar controlled, main driving chain to be protected in some way, and a better catch for the stand.
Speaking generally, the Scott is beautifully made: Every nut fits perfectly and secured by a spring washer; so nothing seems to want to come adrift. and the tools provided in the tool case fit all nuts, etc, quite well. I wish I had the time to ride in the Quarterly and End-to-end Trials; nevertheless, I hope to see the Scott carrying some riders well to the fore this year.
Following comments in the press about the fuel consumption of two strokes this enthusiast was keen to put the record straight.
I AM A VERY enthusiastic rider of one of the 1910 3½hp models of this make, and cannot understand how it is you find its petrol consumption so heavy. Since reading the article I have made careful tests with my machine, and find I can easily average 70 to 75mpg. A friend and myself, both mounted on Scotts, recently did 155 miles on two gallons of spirit; this run was by no means a non-stop, neither was it over flat country (nor were we under 20mph all the time), but when you take into consideration the fact of its being a two-stroke engine, I think the machine very economical and can be very favourably compared with the average four-cycle twins. As regards the Scott being capable of holding its own with the best 3½hp singles of orthodox type, there is no doubt about this, as my experiences so far lead me to believe that a goodly number of 5hp twins will have their work cut out to keep up with them; leave them, the majority of the standard twins cannot. I rode a fast 3½hp. last year, but it was not a patch on the Scott in any respect. I have no fault to find with the machine; it is not perfect yet, we know, but it is, to say the least of it, five years ahead of anything else.