Several of you asked for details of the Yamaha TZ700 racing bike. Here are some black/white pictures of the early examples.
In the second production run many modifications took place. But that is another story!
Yamaha TZ700 (750) A
This big capacity racer, which Yamaha built in order to compete in Daytona and other 750 cc class races, is technically also a very interesting motorcycle. All the expertise that Yamaha had gained in the 250 cc and 350 cc World Championship classes production racers was “assembled” into the Yamaha TZ700. The following pictures are details from a machine from the first production run for the 1974 season, i.e. starting with frame number 409-000101, ending with 409-000313, so 213 bikes, which were all built before Daytona in 1974.
The nice girl on the Tokyo Motor Show in the Autumn of 1973 (she probably had no idea why she was standing there, I think) has to promote the “Beast”! You can see that that early machine did not even have a strap around the exhaust pipes!
One of the race team mechanics is busy checking a converted production machine, to be used for Daytona in 1974. The bike already has the exhaust pipe strap here and look at the quick-filling device on the fuel tank.
The Daytona machine was virtually identical with the production version. The brake callipers were actually the same as on the TX750 and XS650, only the pads were different. Also the disc brake brackets came straight from the TX750. This machine is the bike that brought Giacomo Agostini his famous first win for Yamaha in Daytona. Giacomo always had his brake pedal on the left and the gearchange pedal on the right, in the true old fashioned European (or M.V. Agusta) way! Here the machine is warmed-up by Suzuki-San, who is long-time retired now.
Opening the engine you see the clever layout of the motor. Two crankshafts as per TZ350 (most parts have different numbers) have on the inside a keyed gear which transmits the power to the primary gear. That shaft also drives the oil pump and the water pump . The small shaft on the left is for the ignition rotor.
Complete with the upper crankcase it still is a big engine.
All the shafts in place for assembly. The large diameter clutch, which is not shown here, has similar dimensions as the XS650 clutch. The steel plates have the same part number 256-16325-00! But is has 7 friction plates and 6 steel plates.
The TZ700 cylinders are equipped with reed-valves, normal DT2 (311 type) production ones. You can clearly see Yamaha’s famous “7” port in the inlet.
The cylinderhead is very similar to the TZ350 too, only some minor differences.
The TZ350 motors had a slightly angled spark plug, here it is a straight fit.
The crankshaft has different webs, but the conrod is the normal 328 type.
On the right hand side you see the slot for the key that holds the gear in place.
Pistons are of course different from the ones on the TZ350 as they have the “windows” for the reed valve induction.
The rear of the TZ700 cylinders show “347 cc” (type) 40900.
The engine was firmly fastened to the frame with 4 long 10 mm bolts, 2 on the bottom frame rails, 1 at the back above the clutch and 1 on front just under the exhausts.
This shows clearly the “doubling-up” from many TZ350 items, like water pipe joints, thermostat/housing, etc.
The fuel petcock was a very complicated piece of workmanship.
Maintenance was not too difficult when only the top end had to be done. Without loosening the engine bolts cylinders and heads could be removed.
The machine here on the picture has the alternative l.h. foot brake. It consisted out of a few optional parts, like (logically) a different brake pedal, spring and longer brake hose.
The Dutch Yamaha Importer received a few early bikes, out of the crate this one also had no exhaust pipe strap.
The engine number of this racer was 409-000101 as you can see on the crankcase.