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longa
Quasi manico
387 Posts |
 Posted - 21 Apr 2006 : 22:30:26
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Per chi ha la pazienza di leggerlo, tratto dal forum tz350.net, il racconto dei records conquistati a Bonneville da Scott Guthrie sulla sua TZ 750 e (prima) TZ 700.
Ispirazione per qualche membro del forum tecnicamente superdotato??
Through the years, there have been several fast TZ750's at Bonneville. I am fortunate that mine was (and is still) the fastest, with a one-way full mile average speed of 203+ MPH. The next day, I made a two-way average of two full miles at over 201 MPH. This was with a 700cc twin-shock bike (I couldn't afford the 750cc kit at the time.)
I believe that I am the only person, and that this is the only "open wheel" (non-streamliner) TZ750 to be officially timed at over 200 MPH.
With the same basic bike, and about a bushel basket of parts, I also could set records in the 125, 175, 250, 350, 500,650, 750 and 1000cc classes. If you go the BONNEVILLE MOTORCYCLE RECORDS SECTION, of the SCTA website, you will see that a number of my records on TZ's still stand. http://www.scta-bni.org/ You might look closely at the 750cc records section.
The TZ750 can be configured in a number of interesting ways by eliminating some of the individual cylinders, or by changine the bore on cylinders. By using the outside flywheel on the crank, and pairing it with the flywheel that connects to the crank drive gear, the outside cylinder can be eliminated. I first did this to creat a single-cylinder engine for dyno work. LOTS easier to just modify one cylinder, or make one pipe than four!
By adding the same sort of single-cylinder crank on the oposite side, a twin can be created, either 360 degree, or 180 degree. Add a standard crank, and you've got a triple, all standard cranks, and you have the usual 4-cylinder.
Put a 250cc cylinder on the single-crank engine, and presto, 125cc's. put on the 350cc cylinder, and 175cc engine results. put on the 375cc top end, and 187cc's are displaced. Put the 250, 350 or 375cc tops on the "twin" lower end, and 250, 350 or 375 cc's are counted.
The "triple" can be set up as 375cc's (125 cylinders x 3) or 475cc's (350 + 125), or even 562cc's ( 375+187) The standard lower end can be fit with 2 x 250 tops for 500cc's, with 250 + 350cc = 600cc's, 350 x 2 = 700cc's, 375 x 2 = 750cc's.
In the 1960's, some Europeans ran their 350cc TZ's with off-set crank pins to "stroke" their TZ350's to just over 351cc's. This allowed them, with just a crank change, to run in the 500cc class. In 1985 at Bonneville, I ran just such off-set crank pins in the RIGHT HAND crank of my TZ750, with a result of 751cc's. This allowed me to set 4 records in the 1000cc class. At inspection, the "car guys" were surprised to find a bike with two different strokes in the same engine. They were even more surprised later in the week.
After 4 records in the litre class, I substituted a (1973)TZ250A top end that I had purchased from Don Vesco unto the left side of the bike, for a 376cc + 250cc = 626cc engine, well suited for the 650cc class. The bike gathered two more records, which still stand, more than 20 years later. The inspecting "car guys" were even more surprised to find an engine with 2 different bores (54mm vs 66 mm), and two different strokes.
Fine student's of the horsepower arts will remember that in the late 1990's, I ran a 600cc setup at the BRUTE HOWSEPOWER SHOOTOUT at Daytona Beach, and won the 650cc class. This bike was done up with a 250G top end on the left side of the bike (36mm powerjet lectrons), and a 350G top end on the right with 38MM lectrons. Synchronizing the carbs was a problem, but the bike won it's class with a showing of 148 Rear Wheel Horsepower. Matter of public record.
That bike is waiting for Bonneville!
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