TZ350 and 250 Website

5 Фев 2015 | Author: | Комментарии к записи TZ350 and 250 Website отключены
Honda VFR 750 R / RC 30

Click on these links for a hot lap of the and 250 Website:

Big Brothers

Right the conception of Yamaha’s all conquering and 250 the factory was already developing a 4 cylinder doubled up version of the twin. By casting special, engine cases, to allow the of what was, essentially ( not exactly ), a pair of 350 top ends, had created an in-line 4 cylinder 2 production racer engine, in the capacity.

Picture: Kerry TZ750B

Despite releasing different models of factory GP race bikes for the contracted top riders to use, it wasn’t the end of the decade that Yamaha their production 500cc GP Unlike the 750, this was a little more unique compared to the smaller capacity

The mighty TZ 750

In 1972 Suzuki the world at the Daytona 200 by turning up a brace of watercooled, 750cc cylinder racers producing an (for the early 70’s) Unfortunately for them, all of the bikes due mainly to the power destroying rear tyres.

The cards were on the table, knew they had to do something to this threat and also of Kawasaki’s immensely fast, yet at un-reliable KR750, if it was to have any in the new Formula 750 class. A prototype was and Kel Carruthers tested it, coming believing the approximate 90bhp it was was lazy and the bike was capable of a lot He was right.

Yamaha unleashed first production 4 cylinder 750 two racer monster on the public in 1974, in the shape of the awesome Priced at around $Aus3,500 bike had in fact been development as early as 1971. ground-breaking model weighed in at dry and produced 90bhp @ 10,500rpm it’s watercooled 694cc Formidable figures in the early by any standard.

Interestingly, Yamaha the bike had the potential to produce 140bhp with TZ350 fitted.

Picture: TZ750A ( Joris van de Wiele )

Technically, very similar to the TZ350 it differed in a few crucial areas, being:

1. The head’s squish band was from the 350’s 2.0mm to 1mm and combustion chamber was made a deeper so as to keep the compression to 7.3:1.

2. The exhaust port was 1.5mm and four petal valves added to help the influx of fuel mixture the 34mm Mikuni carbs and to tame the power delivery of awesome machine. along an additional fifth transfer inlet port if you like.

3. The dia. pistons had inlet cast into their though a few of the early examples did not this.

4. The four cylinder order was 1 and 4 (simultaneously) then 2 and 3.

Due to the the factory had trying to fit the four expansion chambers underneath the they chose to make the section of each basically box to utilise the limited space Unfortunately the shape caused the to be prone to splitting open, a rectified by owners and tuners by cutting each pipe and welding short pieces of wire across in an X pattern as a measure. Other problems as cylinder head nuts causing water leaks and bearings seizing appeared at as well.

From the A model the TZ750 minor improvements for the following B. There were just an up-rated waterpump to better the cooling duties for the four cylinders, strengthening of the split-prone a beefed up chain tensioner, a of gears were improved and importantly, an increase in bore to 66.4mm to take the formerly machine out to a full 747cc, the first 46 B’s were with the smaller capacity, after these bikes off the production line did the bigger appear. (Click here for on new TZ750 piston kits for The improved chain tensioner was welcome because one component really copped a beating on a was the drive chain. Savvy eventually worked out that the needed to be pre-stretched in order to the distance in a longer event !

The C was unchanged from the B and was really a way the factory could supply the big to those in need while the D was developed and produced.

Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30

The OW31 racer was released around time. Motor-wise the bike had 6 ports per cylinder, unlike the TZ750’s. Other improvements the customer 750’s were amounts of titanium and magnesium to 18kg in weight and a mono-shock (Picture: OW31 factory shot supplied by Tim Keyes.)

( OW31 cylinder, courtesy of )

1977’s TZ750 D was marketed by as a works OW31 replica and as a a high percentage of ( though not all ) like to claim their Ds are when in fact they are more than a mono-shock C mufflers. (Still an absolutely machine none-the-less.) None of the metals or components from the were used on the D, obviously to costs down. The only to the motor were alterations to the exhaust ports, jetting, and ignition wiring.

Other components to receive an were the exhausts, which now had the hand outer pipe around behind the carbs to the chambers underneath the motor to be the round section. The exhausts also now fitted with and the frame bracing was increased. about 20 or so genuine OW31’s produced that year, and 10 more (30) TZ750 Ds.

The Ds for Ј7,000 including a spares

Over the next two years, and 1979, 162 more of the OW31 TZ750’s were made. the bikes remained basically from the D model, apart 6 petal reed valves introduced, though with an of 120bhp @ 11,000rpm utilising a 747cc and pushing just dry, they were not to be ( They say the roofs of the transfers had angles changed with the F, this is unconfirmed.)

Picture: factory shot (Courtesy Hulme)

Sadly, the FIM dropped the 750 class from World status in 1979, effectively the TZ750’s reign.

Apart from competitively in various Formula One classes the world until 1983, and of today’s Forgotten Era class the beast has become little than a fond memory of who raced, worked on, and observed incredible machine. Not forgetting of a truly prized possession of the few who still own one.

The last F was sold in January 1983.

Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30
Honda VFR 750 R / RC 30


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