This project was about a life long passion for automotive and mechanical design. Enjoying freedom with friends and tuning to the best of our ability, learning and building the dream machines of the time.
After owning the motorcycle for 4 years, it was time to strip, refurbish, replace and rebuild almost the entire machine. The focus of the design was then to build a more Road/Street biased motorcycle out of it.
The chassis was stripped and Powder Coated ready to accept new bearings and rebuilt suspension components.
The engine was refreshed with a modified 134cc TZR barrel and cylinder head with revised port timings and power-valve.
Replacement or restored hardware was used throughout.
Firstly, replacing the swingarm for a lighter aluminium design taken from a Yamaha WR200. Custom Drop Links were designed and made to work with the new shock absorber length and ride height change for quicker steering.
Machine polished upgraded WR200 Swingarm
Frame Geometry borrowed from a Yamaha WR200
Swingarm length and pivot points now require custom Suspension Links to be made
Water Jet Cut - Stainless Suspension Links, these were designed to a preferred ride height which in turn favoured less Rake angle for quicker steering
Tolerance was achieved by post processing the bearing faces using a larger drill bit
Parts were organised and stored ready for reassembly.
One of the biggest differences to classic motorcycles like the DT125R in this project to a modern motorcycle is the braking performance.
To be able to maintain a chassis balance with the modified engine both front and rear brake systems were upgraded. Front disc size was increased from 210mm to 298mm and from a Single Pot Calliper to a Twin Pot Calliper design which allows a larger brake pad to be used.
The front calliper upgrade was achieved using parts from other Yamaha models mated with a custom designed bracket to fit the original front suspension.
Starting quick and dirty with a wooden template and washers, this was done to help visualise the clearances needed to mount the upgraded calliper. This was then transferred into CAD where a DXF could be produced and the final Water Jet cut 7mm Stainless plate completes the design.
To achieve the most performance and to help manage supporting modifications such as Fuel, Carburettor and differing Exhaust designs, a programmable Capacitive Discharge Ignition (CDI) was used to control the Ignition timing, Rev limit and Power-Valve timing for the engine.
A custom mount needed to be made with a design that would act as a heat sink, allow easy access for connection to a PC for tuning and fix to an area of the motorcycle that was less vulnerable to direct water spray.
A completed chassis refresh of this 20 year old motorcycle then left Carburettor and Intake tuning to experiment with.
Lots of parts were used from other models of motorcycle as upgrades. This was done researching photographs and comparing dimensions with sellers across the world. Resources such as Repair Manuals and New Old Stock (NOS) distributors gave many reference images and diagrams which were used to determine elements which may need to be modified or would fit the chassis.
Parts non original to the motorcycle used were:
'2005 Yamaha YZ250 - Throttle Housing
'1991 Yamaha YZ125 - Throttle Cable
'2004 Yamaha YZ125 - ASV Clutch Perch & Lever
'1989 Yamaha YZ - Clutch Cable
'1992 Yamaha TZR250 - Rev Counter
'1999 Yamaha WR400 - Headlight Housing & Lamp
'2001 Ducati 900S - Front Brake Master Cylinder
'2007 Yamaha DT125X - Brembo Front Brake Calliper
'2014 Yamaha YZ450 - Front Brake Line
'2005 Yamaha DT125X - Front Wheel, Brake Disc
'2005 Yamaha DT125X - Rear Wheel
'2005 Yamaha DT125X - Speedo Drive
'1992 Yamaha WR200 - Side Stand
'1992 Yamaha WR200 - Radiator & Hoses
'1992 Yamaha WR200 - Swingarm & rear Spindle
'1992 Yamaha WR200 - Rear Brake Calliper
'1995 Yamaha WR200 - Water Pump Housing & Coolant Pipe
'1992 Yamaha TZR 4DL - Engine Covers
Yamaha WR200 - FMF Exhaust Silencer
'2007 Yamaha TDM 750 - Rear Brake Master Cylinder
'1987 Yamaha YZ490 - Rear Shock Absorber
'1992 Yamaha WR200 - Inlet Manifold
'2001 Aprilia RS250 - Carburettor