I'll be honest here, I bought this bike on its looks alone. I saw it in the dealers and it made me smile. There's just no other bike that has the TDR's looks!
The TDR shares many components with Yamaha's other 2 stroke 125's: the DT dirtbike and the TZR race replica. The engine and gearing are exactly the same as the DT - a watercooled 2 stroke with crankcase reed valve induction. The TDR accelerates quickly like a dirt bike but doesn't have a very high top end. The frame is the super stiff steel deltabox variety and this combined with the suspension and wheels makes for great handling. The frame is so stiff it could easily handle an engine kicking out 2 or 3 times the power of the TDR's. The seat is high up off the ground, again similar to the DT. The wheels sizes are 18" front and 17" rear. If you are under 5"7 you might want to check you can get your feet on the ground first.
The handlebars are wide and the seat well padded and comfy. The twin headlights are very powerful making bad weather or night riding no problem at all. Fit Philips Blue Vision bulbs for the
finishing touch. Underneath the seat there is space for a U lock, a toolkit, mobile phone and wet weather gear. The brakes are up to the usual high Yamaha standard. The front brake is almost too good: slamming it on at 30mph results in the rear end lifting nicely. Lots of fun!
2 stroke 125's have the advantage over 4 strokes in that they have to be restricted in order to qualify for the 12bhp/60mph learner laws. In the TDR's case, the powervalve and exhaust limit the bike - max revs are 8,000 rpm which is about 60mph in top gear. This is great for learners and once you have passed your test you can get it derestricted.
To derestrict the bike, the dealer will rotate the powervalve so it can open fully at high rpm and remove the restrictor from the exhaust manifold. This will allow the bike to rev right up into the redline which is where 2 strokes make all their power. Restricted the bike gets 70mpg, derestricted gets 60mpg. Getting the exhaust/reeds/gearing changed will lower this further to 55mpg and changing the jets will drop it to just under 50mpg. The tank holds 11litres. Expect around 115 miles from a full tank and a further 15 from reserve.
My TDR came fitted with a Powervalve servo motor. Although it was set to the closed position whilst restricted, once derestricted the servo opened the exhaust port above 7,000 rpm. If you don't have a servo motor and set the port to stay permanently open you will rob the bike of low down power and once the RPM's slowly get to 7,000 the top end power will suddenly kick in making the front end lift. As far as I am aware, all official UK TDR's came with a Powervalve servo motor to ensure riders had the best of both worlds - low down pulling power and top end power. If for some reason your model does not have this then getting hold of one is the most cost effective upgrade you can do to the TDR.
Unfortunately someone at Yamaha decided to put a catalytic converter in the TDR's exhaust chamber which makes a slow bike even slower. Yes, you read that correctly: a catalyser on a 125cc 2 stroke! Even derestricted the bike struggles to maintain 70mph. Bear in mind this bike weighs 130kg so it's around 20kgs heavier than most other 125's. The gearing doesn't help either: a 16 tooth gearbox sprocket and 57 tooth rear wheel sprocket makes for great acceleration to 50mph, but as you crawl up to 70mph the rpm's are nearing the 10,000 redline. Not good if you value your engine.
In order to really release the potential of this little bike you need to replace the whole exhaust with an aftermarket variety: an Arrow system is the best. This is far lighter than the original Yamaha and looks and sounds great. There are no silly restrictors and best of all no catalytic converter! This system really makes use of the TDR's derestricted power and at 7,000 rpm the 2 stroke powerband kicks in and off you go.
The next thing that needs to be sorted is the gearing. The most popular modification is to swap the 16 tooth gearbox sprocket for a 17 tooth version. This will lower the rpms by about 500rpm for each gear. So 60mph will be 7,500 rpm, 70mph will be 8,500 rpm, 80mph will be 9,500rpm and 90mph will be just going into the redline at 10,500rpm. The bike will happily buzz along at 70mph all day without revving its nuts off like it did before. This will help to preserve the life of the engine and cut down on top end rebuilds. Always use top quality fully synthetic oil with 2 strokes.
Other popular modifications to the TDR include replacing the standard Yamaha steel reeds in the reed valve with fibre ones. These allow more air/fuel in for a better burn and more power at high rpm. The spark plug can be upgraded to a Splitfire type SF406B (equivalent to NGK BR9ES).
I would not recommend changing the main jet in the carb as the TDR only has an 11litre tank and bigger jets will lower your fuel economy and drop the tank range from 115miles to 90miles. They only provide a small power boost above 9,000rpm. If you wish to perform this modification, replace the stock 270 main jet for a 290 or 320 type. This also requires drilling holes in the lid of the air filter box in order to allow more air in. Keep an eye on your engine temperature and check your spark plug colour regularly to make sure the fuel/air mixture is correct. The engine must not run too hot otherwise damage will occur.
The wide (for a 125) wheel sizes are 100/90-18 front and 130/80-17 rear and these allow decent rubber to be fitted. Bridgestone Battlax BT45's are the best for road use and they even work pretty well going down gravel and dirt tracks as long as it's dry. If you really want to hit the muddy stuff, the Bridgestone Trail Wing tyre will be better. Although the TDR is not a proper off road bike -its a supermoto- a street bike with off road bike looks. Buy a DT if you are serious about off roading. Dropping the TDR at speed can be expensive with upper fairing and rear panels being vulnerable to smashing if you loose the front end getting caught in a rut whilst off road.
Getting this bike properly de-restricted is really worth it. The suspension and frame easily cope with fast 70-80mph cornering, and the engine will happily run and run as long as you keep the revs around 9,000 rpm which is 75mph with the gearing mod done. Flat out is around 85mph. This is a pretty good speed for a 125cc supermoto. You can't keep up with the 33bhp super sports 125's such as the Cagiva Mito or Aprilia RS but then the TDR doesn't go horribly wrong as much as they do!
The TDR proves that you don't need to be doing 100mph to have fun on two wheels. Buy one, derestrict/mod it, hit that 2 stroke powerband and thousands of miles later it'll still make you grin.
How helpful would this review be to a person making a buying decision? Rating guidelines
very helpful by (100%):
