Yamaha TX 750

The TX750 is a two-cylinder standard motorcycle built by Yamaha. The bike was released in 1972. Significant reliability problems affected the engines in early bikes. Yamaha made several changes to solve the problems but the bike was withdrawn from most markets after 1974 and production stopped in the home market after 1975.

Like Yamaha's earlier XS650, the TX750's engine was a vertical air-cooled parallel twin with a 360° crankshaft, a chain-driven single overhead cam, and two valves per cylinder. The engine was aluminum with a horizontally split crankcase and steel liners in the cylinder bores. The intake system was fed by two 38 mm Mikuni Solex carburetors.

New features in this engine included a positive crankcase ventilation system, hardened valve seats suitable for unleaded fuel and a balance tube in a cast manifold that connected the two exhaust ports together on the front of the engine. The balance of the 2-into-2 exhaust system were dual up-swept pipes with megaphone ends.

The engine used automotive-style plain bearings for the major rotating components. Three bearings were used for the crankshaft and two for the camshaft. The choice of bearings necessitated the use of a high-pressure lubrication system, which in the TX750 was a dry-sump system with two Eaton-type trochoidal pumps; one for pressure and one for scavenge.

Yamaha claimed 63 hp (47.0 kW) @ 7500 rpm and 50.6 lb⋅ft (7.0 kg⋅m) @ 6000 rpm. The engine had a more restrictive exhaust in the German market, which lowered output power to 51 hp (38.0 kW) and torque to 42.6 lb⋅ft (57.8 N⋅m). Some reviews of the bike report other differences, such as 8.4:1 compression ratios and 32 mm carburetors, but it is not clear whether these were changes for specific markets or running production changes.

Yamaha designed the engine with a unique oil-filter located in an unusual location. Replacement filters are difficult to find, and adapters that allow the use of more commonly available filters have appeared in the aftermarket.

To counteract the vibration that occurs naturally in a parallel twin, Yamaha introduced a system they called the "Omni-Phase balancer". The Omni-Phase system used one chain-driven weighted shaft in the engine sump rotating in the direction opposite that of the crankshaft to counteract forces created by the pistons moving up and down the inclined axis of the piston bores. A second shaft with weights rotating in the same direction as the crankshaft counteracted the force couple created by the difference in the vertical height of the fore-and-aft forces created by the crankshaft and the first balance shaft. The Omni-Phase balance system consumed some engine power to operate.
In early production models sold in Japan, Yamaha used a spring-loaded chain-tensioner to control lash on the chain driving the Omni-Phase balancer, but this was later changed to drive sprockets with a 1 mm offset which controlled chain lash while offering longer chain life and reduced noise.
Both kick-start and electric-start were standard. The electric start added a third chain to the engine's internals. The engine did not have a decompressor. The five-speed fully meshed sequential transmission came from the earlier XS650. The sprocket sizes were 17 front, 40 rear, connected by a #530 chain.

The TX750 instrument package included four lamps that warned of various problems. The upper lamp would light whenever the main headlamp was burnt out, while also sending power to a secondary filament. Below this was a lamp that came on when the thickness of the rear brake shoe fell below a specific amount. To the left of that lamp was an oil pressure warning light, and on the right a lamp that would glow solid red whenever the brakes were applied, and would blink red if the rear lamp was burnt out.

The TX750 had a double-cradle frame of tubular steel.

Front suspension was a hydraulically-damped telescopic fork with 5.9 in (150 mm) of travel and coil springs with a rate of 2.98 lb⋅ft (4.0 N⋅m). There were no gaiters on the 1.4 in (36 mm) standpipes. A vane-type steering damper was fitted.

At the rear was a steel swing-arm that rode in plain bearings. Springing and damping were provided by dual shock absorbers and progressively wound coil springs whose rate varied from 9.83–11.5 lb⋅ft (13.3–15.6 N⋅m) and provided 3 in (76 mm) of travel. The rear-shocks were five-way adjustable units.

The TX750 was the first Yamaha road bike to have aluminum wheel rims. The rims were copies of Akront valanced rims made by DID.
In Europe

The TX750 had dual front disc brakes with dual expanding pistons on 11.8 in (300 mm) discs. In Japan, the United States, and other markets the bike had a single disc, although the lugs needed to mount a second disc were in place. On all bikes the rear brake was a 7.1 in (180 mm) drum with an internally expanding single leading shoe.

The front wheel mounted a 3.50 - 19 - 4PR tire while a 4.00 - 18 - 4PR tire was on the rear.
The bodywork was finished with a metal-flake paint.

Source wikipedia.