The Scene
THE SCENE
BY IVAN J. WAGAR
LATEST photos of the 125cc Yamaha GP racer reveal an unusually complex seven-and-a-half cubic inch motorcycle. The results sheets indicate that the effort was well spent, for Bill Ivy has been a rather good match against the Honda fives, even though Taveri is almost certain to pick up the 125 crown for 1966.
The engine is the now proven water-cooled twin which, like all the liquid-cooled racers, employs the thermo-siphon method of water circulation, therefore eliminating the need of a pump and its inherent drive and reliability problems. Yamaha has now fitted a carburetor with built in float chamber, quite similar to the racing Keihins used by Honda. Behind the carburetor, above the clutch, is the oil pump, which feeds the gearbox and engine main bearings.
This layout has proven so successful, that while the two-fifty four stands almost no hope against the Honda-Hailwood combination, rumors have it we can expect to see a quarter-liter version for next year. If this is true, and it is certainly logical, then Yamaha will be the second firm to give up on four-cylinders. Suzuki, too, found fours to’be cumbersome and difficult to ride, and often lost out to machines with much less horsepower. I cannot help but feel that Read would have done better with the older RD 56 model, because this year it seems he has been riding harder but enjoying it less, especially since he lost the title.
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WE have received numerous letters requesting tuning information on the popular new Yamaha YL1 lOOcc twin for racing. These little machines are being used extensively in Japan and have proven very successful in road racing, while gaining their share of scrambles victories as well.
The Yamaha factory will, in a few months, have GYT (Genuine Yamaha Tuning) kits for the YL1, similar to the present kits for YA6 and 80cc models. In the meantime, the information found here will help those who wish to do the work themselves, or cannot wait.
Cylinder porting can be modified according to drawing. Any dimensions not given are standard. It is not necessary to do a great deal of work in the ports, since their as-cast finish is already quite good. The piston should have 5mm removed from its bottom, leaving out the lower piston ring, and after running the engine for five miles, the piston should then be checked for high spots. These will have a bright shiny appearance and should be carefully removed with a fine file. It may be necessary to repeat this precedure two or three times, until all indications of high spots are eliminated.
Compression can be increased by machining 0.060-inch from the cylinder head face, but be very careful to cut a new 20-degree bevel around the combustion chamber. This is important, as this relief becomes the squish area when the engine is operating, and insufficient bevel will cause the piston to contact this point.
In standard form, the YL1 uses a medium reach plug, but with the higher compression ratio it will be necessary to run a plug that is colder than available in medium reach sizes. The plug should be at least a B-10 EN or possibly Bll EN, since these are long reach; extra washers may be used to shim the plugs. Washers should be solid copper and free of carbon or dirt. This is extremely important, especially when dealing with more than one washer, as there is more chance of the plug being partially insulated, therefore running hotter.
An expansion chamber for peak power at high rpm should be used for road racing or fast scrambling and TT racing. The pipe shown here will give excellent results at high engine speeds. A power increase will also be obtained if the carburetors are opened to 16mm. However, if this is done, the intake ports should be matched to the new choke size in order to obtain maximum gain. Larger carburetor jets will be required.
A worthwhile increase, in the case of all-out racing may be had by converting to total loss ignition, using only the battery, breaker points and ignition coils. The armature can be removed completely from its shaft by turning in a lathe until only the shaft remains. Disconnect armature, field coil wiring and the field windings can be taken from the generator case and tossed away. At this point, anything that is not required for racing should be stripped from the machine to save every ounce of weight possible.
The YA6 (125cc) clutch assembly will fit and ensure reliability under the strains of racing and increased power output. For road racing, a 15 or 16-tooth countershaft sprocket can be used, along with 31 to 35-tooth rear, depending on course conditions and rider weight.
If one so desires, the Autolube system may be removed by taking out the pump and covering the hole with a special plate, part number A6B0848. The oil feed holes in the intake ports must be plugged, and any good grade two-stroke oil may be used at 15 or 16 to 1 mix.
It must be remembered that information given here is not recommended for machines that may sometimes be used on streets or public roads. Racing expansion chambers are very loud, and very illegal, and unless one has serious racing in mind, these modifications should be treated with discretion.
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No discussion about characters would be complete if we missed Bert Munro, a 68-year-young New Zealander, who has become one of the best known, most admired individuals on the Bonneville scene.
When I met Bert last year, we talked about a fellow countryman of his that, until meeting Bert, I was sure had to be the world’s champion “nut.” His name was Peter Murphy. We did the Isle of Man, the Ulster and some short circuits together, and no matter how badly things were going (they were usually pretty bad), one could rely on Peter to pull off a beautiful stunt. After meeting Bert, I found Peter had been taught by the master jokester, as they live only a short distance apart and have been friends for years.
Bert built a new house in New Zealand, and was informed by a building inspector that it did not meet the code. He simply moved into the garage with his motorcycle, and still lives there. The house is empty! He is somewhat of a Paul Bunyan and Mike Hailwood all rolled into one. He does not smoke or drink and goes to bed early. And if you’re rising at six a.m. at Bonneville and see Bert already up and about, you just know he has already been up and done a half a day’s work. He bought his Indian Scout new in 1920. He was 21 years old at the time and rode it to work for six years. A thousand stories can be told about the man and his machine between then and now — all funny.
At one point in the development of his 1920 Indian, new pistons were required.
Bert dug some little holes in the ground, poured in some molten aluminum, then went back to his $22.00 lathe and finishturned the pistons that are in the engine now. On the same lathe, he turned the cylinder sleeves from three-inch sewer pipe.
Persistent connecting trouble led Bert to cut up an old Ford front axle, and with only a hacksaw and file, he made the rods. The original Indian flywheels were not taking the revs and horsepower very well, so the ol’ man hacksawed two slices off a Caterpillar axle-shaft and took them to a friend with a heat-treating furnace. When they were heated to bright red, Bert pulled them out and beat on them with a sledge hammer. The process was repeated, until it was felt the wheels had been sufficiently “forged.” The handmade aluminum fairing took five years to build and looks like a stamping from Detroit.
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Admittedly, this all sounds rather “Goldberg,” but Bert has turned 195 mph. His goal this year is to break Bill Johnson’s 224.57 mph record. Bert has spent the past month with his sponsor, Sam Pierce, and a few weeks ago, for the first time in his life, the eager Kiwi used a milling machine. His only comment was “Gee, it would be easy to build a motorcycle if you had one of these things.” The worst insult you could come up with would be to call the machine an “old” Indian. He has kept track of the times it has blown up — 157 times to date — and says, “What do you mean old. It has been re-engineered 157 times.” Seeing a man with such spirit such as Bert’s, how can anyone help but hope he will break the record this year?
WHILE we read about exotic European and Japanese multis, one of motorcycling’s great characters has created a four-cylinder bomb virtually under our noses. But to appreciate the motorcycle, you have to know the man. CYCLE WORLD did a story on Speedy Babbs in the Jan.
1965 issue, and we are happy to find Speedy has not changed one ounce. Although a few crashes have curtailed his “Globe of Death — The Man From Mars” act, Speedy is busy building a Silodrome in Stuart, Florida; but for recreation he and Ollie Raunser, of West Palm Beach, decided to out-do the Count a bit and toss together their own four.
With the help of such refined production equipment as a hacksaw, bench vise and a welding torch, they have come up with a creation that Speedy refers to as “The Monstrosity.” The main frame is basically Indian Chief, which employs the now extinct plunger rear suspension. To give the “Monstrosity” a modern flair, Speedy mounted a pair of telescopic front forks from a long-gone Indian Arrow.
Heart of the beast, and this was a wise choice, is one of the very good McCulloch air-cooled, two-stroke opposed fours, which were built to power target drones and can still be found in surplus yards. Speedy then made a housing to couple the engine to a BMW transmission, the drive being fed through a BMW drive shaft to a standard rear wheel of the same make.
The whole thing started as a “lark,” to build a one-off as a conversation piece, but as it neared completion the boys found they might really have something. Speedy became so serious that he fitted a 300-mph aircraft speedometer, which he claims “will tell whether I have a head or tail wind, when I compare it to my regular speedo.”
Now that Speedy has a 72-horsepower motorcycle, which really works, he would like to see a class at Daytona catering to machines of any displacement. He is sure he can beat aircooled Chevy sizes and the like. His proposal is an unlimited displacement category with no restrictions on gearboxes, fuel or supercharging. Only the oval would be used. (I can see why).
All this makes you wonder whether Speedy is serious or kidding. One thing is certain, the “Monstrosity” is born from backyard daredevil ingenuity possessed by men like the Wright brothers, and all too quickly fading from our modern lives. ■
