Trials Taming: Yamaha DT175

The bike I chose was a Yamaha DT175, a ‘76 model, the last of its type with twin rear shocks, with 1100 miles on the clock in as new condition. The handling was quite good considering the knobbly tyres and even the tiny drum brakes seemed adequate. The bike was tall and very comfortable with long travel suspension, although the front forks dived like a rabbit going down a hole (cured by using thicker oil).

The seat was comfy and well padded. The exhaust was an up and over job which crossed sides under the seat, resulting in a warm backside in the winter and potential piles in the summer. Thick cooking foil fixed under the seat meant I did not have to spend any money on pile cream come summer. Because I did a fair amount of off road riding, chains only lasted 2000 to 4000 miles as they were very thin and cheap. Tyres lasted around 6000 miles when they would go square, although still legal they did horrid things to the handling.

Petrol consumption stayed at 55mpg whether I thrashed it up the M1, pottered around trails or whatever. Which brings me to the most serious drawback on this sort of bike. 55mpg isn’t too bad for a seventies two stroke but coupled with a one and half gallon tank it is totally stupid. I must have known the location of every petrol station within a 50 mile radius.

Off road riding was great stuff, the bike could handle most terrain and was light enough to lift out of what it couldn’t manage. I had many tumbles and the majority were harmless to the bike. The design was such that indicators et al never came to any harm.

There were three problems. A hole in the gearbox casing caused by a tumble, cured by Araldite. I painted over the Araldite with silver paint until I could get another casing, but I never bothered as the bodge lasted until I sold the bike, never leaking a drop of oil. The second problem was a slight vibration that slowly became worse - after I'd overtaken a Plod mobile whose ad had asked if it was a suitable vehicle to ride on the motorway. He wasn’t too amused when I said it must've been if it was fast enough to overtake him!

By the time I got home the vibration was horrendous, blurred vision stuff. I really thought it was serious, but it was just a missing engine mounting bolt. After much searching trying to find a nine inch bolt with a half inch diameter, I picked one up at the local car breakers, it was embedded in mud near his hut.

The third problem was more serious as it kept reoccurring. Every now and then the head gasket would blow. The gaskets are made from copper and come in different thicknesses, just like the riders. I had the idea of annealing it. As I was camped out in North Wales at the time and had a handy gas burner upon which to brew me tea, I set about this task. After cooling down my burnt fingers in a nearby stream, I tried it out. Great, no leaks. Whenever I fitted a new gasket after that, when doing the odd decoke, I softened the gasket first. Never had a gasket blow after that.

North Wales brings me to the point again of the daft petrol tank. It may have been very inconvenient for local trips but as halfway through the year I was introduced to the delights and perversities of motorcycle touring by an Irish friend, it took on a whole new dimension. Or lack of it. I made the trip with my Irish friend many times and became awfully familiar with the petrol stations along the length of the A5 from sunny Milton Keynes. All this didn’t stop us going even further afield to the Lake and Peak Districts. We made sure to carry a length of fuel pipe to take some fuel out of his tank when I ran out.

I know it wasn’t designed for touring, but funnily enough it was great for just that, notwithstanding the petrol problem. The comfort was fine, the riding position ideal for cruising along and looking at the scenery. Very laid back. All that stood me in good stead when I went back to faster bikes. I think Yamaha could have given it a larger tank without making it look like those hunchback Paris Dakar things. An extra gallon would have made all the difference.

One thing that was a bind was having no centre stand. At home, I had a handy bucket which fitted neatly under the engine bash plate, dunno what would have happened if I had a puncture. Trail bikes, these days, do have larger petrol tanks but still no centre stand. I owned that Yamaha exactly one year and in that time had done enough riding to put 16890 miles on the mileometer. I really did enjoy my time with the DT and would seriously consider owning one again, but as a second bike. It would be much more sensible for trips to work and down town than my present bike, a 650 Katana. I changed it for a MZ250 with a huge tank, I wonder if a MZ tank would fit a trail bike?

Maintenance was dead easy. The points and timing very rarely needed attention. Decoking was a regular feature despite what people will tell you about Posilube two strokes never needing it. Fortunately, Yamaha had fitted this model with sleeve bolts on the cylinder head which meant you could leave the rest of the gubbins in place and slide the head out sideways. This was done every 2000 miles, or else performance suffered.

The chain needed a lot of care. It was too thin for the bike, coupled with the long length that trail bikes had, it suffered badly. I did try tensioners but they really did not help. The sprockets were flat and straightforward, so if you were really keen the answer would be to go up one size in chains. Lights were summed up by the 25 watt headlight, the 6V 45 watt MZ one was a revelation after that.

To sum up, if you get a chance to sample a small trail bike do so. Most of the models are of a muchness so it's not worth bothering about makes (excluding Hondas, of which I am not a fan). And, if you get the urge to go touring on one, don’t forget to go in the company of a mate with a bike with a large petrol tank and three foot of petrol pipe.

Stephen Bergman