[allisonfrnyork33]

What this did was add a little more power in an ever-narrower powerband. Horsepower and reality were at odds, with Yamaha immodestly claiming 39 mustangs at the crankshaft. However, when the unromantic editors at Cycle magazine had the temerity to put the RD350 on a dyno, they found only 30 thoroughbreds at the rear wheel. In truth, 30 horsepower out of a 350 was not bad, but these came on at 8,000 rpm, and at 6,000 rpm the number dropped to 20; keeping those 20 to 30 horses at full gallop meant doing a lot of shifting, so Yamaha added a sixth gear to the transmission. here

[copsewood]

The Chef Boy 350 was an updating of the venerable R5, a mainstay of the company’s line. In this day of 100-horsepower 600cc sportbikes it takes some mental acuity to go back to when a 350 was considered a two-wheeled weapon of consequence. Kawasaki had come out with its 350 triple, the Suzuki GT380 was no slouch in the performance department, and Yamaha wanted some of that market.

[Kir]

In the middle ‘70s the company had a split personality with its street models, seeing the EPA’s handwriting on the wall: Two-strokes would not be forever. With this understanding Yamaha’s major focus was on the four-stroke TX series—500, 650 and 750 twins, less advertising for the smaller, definitely cheaper two-stroke twins. The 1973 price for the RD350 was $839, while the TX500 came in at $1,350.

[BrandonPetersville99]

Nicknames can be good, flattering, positive…or quite the opposite. In the case of Yamaha’s RD series, the Chef Boy-Ar-Dee moniker—say it slow—was greeted with less than enthusiasm by the company execs in California. After all, that RD was meant to stand for Race Developed, not a can of Americanized overcooked pasta. Grin and bear it.

[scottmacheda]

The engine work made it a little more finicky to ride, but really more fun. You could set the tach at 5,500 in sixth gear and cruise at 70 mph, or keep the engine on the boil and howl along the back roads. The bike was weak on torque, but if the rider happened to hit the powerband in first or second gear, that front wheel would reach for the sky. The suspension was a trifle on the soft side, and various bits could drag in the corners if the rider were cheerfully aggressive, but the great advantage was the new 10.5-inch disc brake on the front wheel, with the caliper having two slave cylinders pushing the opposed pucks that ferociously squeezed the disc. Everybody loved the new brake. On the rear was a standard drum. Tires were a 3.00 x 18 on the front, 3.50 x 18 on the back, with 52 inches between the axle centers.

[NuAngel]

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[baloney]

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[ChesterA321]

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[Andreas Schildbach]

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[BitLex]

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[gazoakley]

[sunglasses]

15. Next, install the new seals in the pump cover and the pump body. The seal for the pump body should be installed flat or rubber side out, the seal for the cover should be installed flat or rubber side in. here

[Mamarok]

18. With the cover secured with new Phillips screws, key the pulley spring to the body. Follow with the pump pulley, turning it counterclockwise under spring pressure until the hole for the roll pin lines up, then install the pin. [links]

[didiertomas2385]

9. The plunger cam has a small oil seal inside its shaft for the pump plunger. Using a small hooked tool, reach in and remove the seal. more

[matsh]

20. With new body to engine gasket in place, install the oil pump to engine using new mounting screws.

[plupumbl0ck1978]

Our factory Yamaha manual specifically says of the pump, “Make no attempt to disassemble it,” yet it can be rebuilt. Pump failure is typically due to bad seals or, as we found with our 1974 Yamaha DT125, sludged or stuck parts. In our case the spring for the pump shaft had rusted in the compressed position. A previous owner bypassed the pump in favor of premixing the fuel/oil, likely because the pump couldn’t stroke with a stuck spring.

[mrorymolina1]

I don't have that engine. I know a few people with engines as old as that though and the autolube system still working fine. Big difference is most I know use their engines on a regular bases. they have not sat around for years, then fired back up, that's when the trouble starts. here

[grrrl]

Is there not a test in the Service manual where you measure how much oil is being pumped over a certain time frame while running the engine on a portable tank with premix in it? Do you have a Yamaha service manual? [links]

[AT-LOW]

but the pump if old
if you are rebuilding the motor, I would replace the oil pump. more

[chorchonga]

Seems like you are doing all the things required to bring this engine back to life.

[eurekafag]

gear driven pump off of the crankshaft.
crank turns and oil pump should too.