Back in 1969, Yamaha were the first to put a trail bike into production and by the mid 70s the idea had caught on in the UK. The delightful DT series created a new way of getting about, and in fine style too.
Modern motorcycles don’t come much simpler than the DT, in the types day it had been the norm to squirt a dose of two-stroke oil into your tank for every gallon filled. Not so with this and most of the new generation of Japanese leisure vehicles, as the Autolube system, once set up and running correctly, takes care of the engines needs leaving the rider little else to do but keep an eye on the oil levels and the tank filled.
The twin shock DT is a small and compact machine, which, before riding it leads most to think of it as little more than a play thing, a paddock bike maybe, but never a serious on or off road machine. It is solidly built however, and, when ridden with skill, is a great mix of competition trial and motocross machinery with the added bonus of being road legal too. The package is wrapped up in a superb piece of tube work, the spindly looking tubes that weld together to form the skeleton, upon which the rest bolts to, is actually a very strong and more than up to the multi tasking that could be asked of it at the drop of a hat. Even the long travel forks and compliant rear suspension are up to the job on tarmac, making for a great ride; the DT could be used, and indeed has been, purely as an on the road commuter bike with ease.
The ideal size and weight, coupled with the right amount of usable power, is to be found in the DT175, it is the size of a 125 machine and yet produces power and torque akin to a 250. Its compact motor sitting high in the frame giving trial bike like ground clearance, while being little wider than the frame loops making for a lithe, and agile machine. The early DT175 engine was also used as the basis for the TY175 competition trials machine, although this was never a serious threat outside of clubmen’s level of the sport, it was still a great starting point for anyone looking to learn the skills involved in this challenging and most skilful of motorsports. The DT is a great introduction into the world of trail riding, even by today’s standards; its mild manners and predictable handling proving to be well up to the job. Owning and restoring one today needn’t be the arduous task that can be the story with classic Japanese machinery, the DT is a fairly common beast and so are the parts needed to keep it in tip top condition. Amazingly, the later monoshock model is still in production for countries in the southern hemisphere, the simple motor and tough chassis proving an ideal workhorse on remote farms and small holdings.
The single pot, two-stroke engine is great low down in the rev range, a mix of clever design, and the 360 degree port timing provided by the reed valve tucked away in the inlet tract, this characteristic alone makes the DT a great bike to be on, the rest of the machines abilities are just a bonus to be discovered as the ride unfolds below you. The engine isn’t just low down grunt, it is very flexible too, allowing it to cruise with ease on the hard stuff, happily topping the UK legal speed limit, although you do have to help out with this task and get down behind the clocks especially if a head wind is encountered. Even so the bike will easily keep up with urban traffic and is a great commuter machine with the added bonus of not having to strictly adhere to the roads should a tasty shortcut through the woods be a more tempting proposition.
On the road the ride is rock steady with no surrender being offered from the knobbly trail tyres, even when a fair bit of lean is added into the equation. Yamaha have judged the needs of this machine almost perfectly, just about every thing works very well on the hard stuff as the weight of the bike is never high enough to overcome the contact with the road. In these modern days of fuel injection and smooth power curves it may come as something of a shock to find that Yamaha had a bit of a handle on the art as far back as the early 70s. Their close work, and association, with Mikuni always meant their machines were among the very best throughout the throttle range. This is no different with the DT and the 24mm, round-slide Mikuni fuels the big bore engine very efficiently, providing a controllable throttle input wherever you find yourself in the rev range, just open the taps and the lively single leaps into action
The same is true off road, and the DT can effortlessly tackle some extreme terrain without further modification from its road set up. The only weak point in the DT’s armoury is the brakes, or the front one to be more precise, the small diameter, single-leading shoe drum stopper up front lacks the commitment needed by such an important member of the team, while the identically sized rear brake often has to be called on to help its buddy out, especially from high speed. At anything above a brisk walking pace, the front brake lever has all the feel of a sponge, the result of a combination cable stretch and drum expansion yields little in the way of solid retardation, you can keep squeezing but there is no noticeable increase in stopping power. This is a most welcome attribute off road however; the front wheel being difficult to lock up on all but the loosest terrain and it soon becomes second nature to rely on the footbrake.
Yamaha DT175 Model history
The Yamaha off road business began in earnest in February 1968 with the launch of the 250cc DT1. Before this point there was always some form of compromise whenever a machine was claimed to be a trail type with road based chassis and engines being press ganged into service with little more that a raised exhaust pipe and a set of off road tyres being fitted. Around the mid 60’s trail riding was something almost unique to the American market and one poorly understood by the Japanese who simply didn’t have the landmass to accommodate hoards of knobbly tyred bikers freely roaming around the land. Once the Japanese had a handle on the idea however the machines suitable for this task came through thick and fast from all manufactures and pretty soon the idea caught on in other countries too.
In 1978 the DT finally got the styling used in the factory’s world championship winning YZ motocross machines. The engine underwent a total redesign that included a six-speed gearbox and a base mounted barrel assembly, the studs that passed though the whole length of the earlier designs cylinder now making way for larger transfer ports. The chassis too was unrecognisable compared to the old style twin shock design that had remained largely unchanged since the original DT1 of the late sixties, in place of the two chrome sprung rear units sat a long single monoshock unit giving inches more travel and a much softer ride.
The front end came in for revision too with thicker and longer travel forks although the pitiful front brake remained unchanged in dimensions although the feel was better thanks to a stronger hub design.
Yamaha DT175 Timeline
A basic twin shock machine with styling based heavily upon the piston port DT1 series.
The DT still looks like a machine from the 60’s albeit a well sat up and alert looking one.
1978 DT175 MX
The first of the monoshock DT series and the machine is finally ready to move on, a beefier 31mm front fork and six-speed gearbox mark the start of a new era for the DT range. A round tube swing arm distinguishes this model for the later box section version both fabricated from steel however despite the latter’s aluminium paint finish.
1979 DT175 MX
There were no significant changes to the second year of production of the DT175MX
1980 DT175 MX
The last of the UK DT175’s before the type made way for the
liquid cooled 125 range. Although identical looking to the 1978 and 79 models the final incarnation of the DT did see some minor yet crucial changes that make life hard for those searching for parts.
Specifications 1976 Yamaha DT175
- Engine – air-cooled single-cylinder reed valve two-stroke
- Capacity – 171 cc
- Bore/stroke – 66 x 50mm
- Power – 15bhp @ 6500rpm
- Torque – 11ft-lb @ 5250rpm
- Carburetion – 24mm MIkuni
- Transmission – 5-speed wet clutch chain final drive
- Frame – steel tube twin cradle
- Suspension – 30mm telescopic forks. Twin shock rear
- Brakes – 130mm single leading shoe drum front and rear
- Wheels – 2.75 x 21, 3.50 x 18
- Weight – 107kgs
- Top speed – 70mph
- Wheelbase – 1246mm
- Fuel capacity – 7ltrs
Yamaha DT175 Gallery