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Difference between revisions of "Yamaha TZ350"
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[[Image:Yamaha-TZ350E-Macau-Museum.jpg|left|thumb|What is essentially a TZ350E on display in the Macau Museum. This bike has an F model top end, Lockheed calipers and magnesium wheels. It also has the gear shift foot lever fitted to the right hand side of the bike indicating that possibly a British rider may have raced it at Macau.]] | [[Image:Yamaha-TZ350E-Macau-Museum.jpg|left|thumb|What is essentially a TZ350E on display in the Macau Museum. This bike has an F model top end, Lockheed calipers and magnesium wheels. It also has the gear shift foot lever fitted to the right hand side of the bike indicating that possibly a British rider may have raced it at Macau.]] | ||
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==TZ350D== | |||
Minor porting, piston and exhaust upgrades saw the peak horsepower output up by 2 to reach a claimed 64bhp @10,500rpm. The factory also chose to fit an offset, angled plug head with the "D", in an effort to combat cylinder and piston distortion as well as slightly raising the compression ratio. New expansion chambers were now fitted from the factory with removable silencers. Small changes were also made to items like the base gasket, crank webs, small end bearings, the gasket for the side oil draining bolt on the gearbox, carby floats and choke systems etc. Tyre widths were also increased from the factory though rim sizes remained as per the previous model. | |||
Not to say that the TZ350 became uncompetitive with the introduction of the "D", quite the contrary, with customer bikes winning 350cc races and domestic championships across the non-USA world from 1977 through 1978. (America didn't run a 350cc class but allowed 350cc bikes to run in other larger capacity classes.) | |||
==TZ350E== | |||
The "E" had a new frame which re-positioned the engine slightly more forward featuring detachable alloy engine plates and around 20 other additional bolts, nuts, washers etc. as well. The swing-arm length remained as for the "D" as did just about everything else apart from the rear lower engine mounting bolt which was lengthened by 5mm. . | |||
==TZ350F== | |||
The introduction of the "F" model in 1979 saw, finally, effective and much anticipated improvements to the now 3 year old TZ 350 C/D/E. Much to the relief of Yamaha devotees, the factory made several changes to the bike, some advantageous, in time owners learnt others were not. They included: | |||
a) The provision of a new "6 port" cylinder, with subsequent improvement in rideability, with an improvement in peak power output to boot. Also new "cross-over" style chambers to keep the muffler tips within FIM requirements length wise and a new piston. The "F" pistons were the first of the short pin "slipper" type but the side windows didn’t have the support web running down the middle, and the ring sometimes pulled the edge of the piston down into the window. | |||
b) A new conrod, which was lighter, but turned out to be prone to failure ( due mainly legend has it, to the wrong silicon content in the pistons causing them to wear and deposit aluminium on the small end bearings causing them to fail and take the conrod with them ), plus a new "3G3" piston to suit the new cylinder. | |||
c) The inclusion of 38mm "Powerjet" Mikuni carburettors to further enhance the new engine's usability through the ability to fine-tune the midrange mixture more effectively and also reduce the risk of seizure at high rpm, while actually contributing to the increase in peak output at the same time. | |||
d) A new, revised, lighter weight frame, which had a bad tendency to fail around the headstock, which is why so many of them were re-inforced in this area, or had aftermarket frames replacing the Yamaha items. (Click here to read about aftermarket TZ frames.) | |||
e) A new box-section aluminium swingarm, aluminium body rear shock (still with adjustable preload and compression damping only). | |||
f) New forks featuring 3-way adjustable spring preload via. an external adjuster on top of each fork tube, as well as revised fork internals designed to reduce the front end "patter" being experienced by a number of 350 riders. | |||
g) A new fairing which dispensed with the separate belly pan and was a sharper shape at the bottom-front (behind the front wheel). The fuel tank was now a tapered shape to match the sloping upper frame rails and the seat unit was changed to a more "current" shape. | |||
h) Minor changes included: the cylinder drain pipe, inner main bearing circlip/washer, gudgeon pins, introduction of an oil level "dipstick" and new ignition pulser coils, exhaust mounts, clutch cover and an additional o-ring was included in the exhaust header to assist sealing. | |||
[[Image:Yamaha-TZ350F-Frame-Failure.jpg|left|thumb|Yamaha TZ350F Frame Failure]] | |||
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Frame failures around the headstock area were a common problem with the "F" model 350's, for this reason a large number of owners chose to ditch the stock frames and replace them with units made by such manufacturers as Nikko Bakker, Bimota, Spondon, Maxton, etc. Others chose to reinforce the stocker with additional bracing such as that shown in the photo. | |||