1992 Yamaha TZR250SP
In 1992 Yamaha only made 500 of these beauties. That was just enough to make it legal for Japanese Super Sport
racing. The TRZ250SP model host many upgrades that the standard model does not have. My goal was to modify
my TZR250SP to bring out its full potential, but still keep it street legal for the highways. |
|
Yamaha's TZR250SP Number 346 of 500 produced
My challenge was make a fast 250 street motorcycle. To do this I would have to derestrict the Japanese 45HP legal motor, update
the suspension and still have it remain street legal.
|
1992 Yamaha TZR250SP
As you can see the Yamaha TZR250SP is a good looking machine. But underneath the body work lies some trick parts. I will try to explain the various modifications I made to my machine. If you have question, feel free to e-mail! |
|
|
|
What Lies Under that body work??
The Motor is Yamaha's 90 degree V twin engine. It incorporates a dry clutch. The cylinders were ported and the heads milled by Stan Stephens out of the U.K. The crank has been polished , balanced , and trued by Falcon engineering. That crank was such a beautiful piece, you almost hated to hide it in the motor were nobody would see it. The TZR crank cases are the same as the TZ race bike. |
Daytona Chambers - Stor Damper & Fox Racing Shock
Daytona chambers hold several Japanese records for 250 Super Sport bikes. My TZR uses Daytona racing chambers with hand made carbon fiber silencers. The fit and craftsmanship are excellent. In addition, a Stor Steering damper is installed to keep things going straight. I had my friends at Fox Racing make me a full race rear shock. This shock has more adjustability than the stock "SP" unit |
|
|
|
Ignition System
An Yamaha Factory racing igintion box is use to boast the over all performance. Top is the Racing box. Below the stock "SP" box. The standard TZR black box number is 3XV-00. The "SP" box 3XV-10. The "SP" box giving a slight performance increase over standard. The Factory Yamaha racing box number is 3XV-80. This box gives you much increase in performance and is the main ingredient to derestriction of the bike. The race box is also need to activate the electronic power jet circuits. I will expalin this in more detail below. |
The TZR250SP Carburetor
The TZR250SP uses 36mm Carburetors. The carburetors use an electronic activated power jet circuit. You can see it sticking down the middle of the intake with the wiring loom on top. This circuit opens up at high RPM's to let more fuel in the motor. In stock form the TZR power jet circuit is not hooked up. You need to full race hardness and race black box for it to be used. However I figured a way around this! |
|
|
|
TZR Jet Kiting
The factory Yamaha race jetting kit was installed. As you can see it consist of all new components.
Recommend Jetting:
.........................Factory..........My TZR
Main Jet...........#260...........#250L #260R
Needle Jet....6FI80-61(3)........6FI180-61(2)
Needle Seat.........#2.5...................#2.5
Pilot Jet................#35.................#35
Needle Value.........3.5mm...............3.5mm
Emulation Tube.XP6536/01........XP6536/01
Needle Jet.................R-2.............R-0
Power Jet..................#60.............#55
Air Screw...................1.5.............1.5
This kit is an important piece to the motorcycle performance.
|
Activating the Power Jets
I aquired one of the racing hardness for the TZR. However I did not want to use it as I needed the lights and all street equipment to be hooked up. I was able to trace the wires to see were they hook up to the black box. I then spliced into the stock hardness and plugged the power jet circuit into it. It worked. I now have them working with the stock hardness. |
|
|
|
TZR Dry Cell Battery
As you can see the TZR battery is a small light weight dry cell unit. This unit lies on its side and is about 2 inches thick. Don't look for one of these at your local bike shops. The only place I have found to buy one of these 12 volt batteries is in Japan. |
Under The Tank
The Stock air box is gone. Under the tank I used heat shield material to keep the hot air from the raditor going into the carburetor. One feature the 'SP" model has over the standard is that the side fairings have air ducts in them. The right side fairing has its duct going straight to the front carburetor's intake. The left side goes to a point under the frame. I ran tubing from their to the rear of the back carburetor. You might see it as the silver tube in the centre of the picture. Now fresh cool air is supplied to the carburetors. |
|
|
|
Daytona Rear Sets
To increase the ground clearance on my favorite canyon road, I installed these beautifully machined rear sets from Daytona racing out of Japan. They are light weight and have excellent workmanship. The controls have a very percise feel. Excellent braking and shifting. |
TZR250 Fronk Brakes and Suspension
This bike has the best brakes from the factory of all the 250 2 strokes. Excellent stopping power and feel. Ferdro brake pads and kevlar brake lines are used. The front suspension is fully adjustable for, preload, compression, and rebound damping. Forks have been re-worked by PPS Suspension Services of California. The "SP" uses 41mm fork tubes as opposed to the 39mm for the standard model. |
|
|
|
Rear Drive Chain
The rear wheel was powdered coated red from the ugly looking grey. Harden aluminum spocket was used. Michelin Pilot "Soft" compound tires are incorporated. Rear tires size used is a 150/60/17. I tired using a 160/70/17, but found the bike handles much better with the 150 size rear tire on it. Kevlar brake line with Ferodo pads are also installed. |
Naked TZR250 !
As you can see, the coolant over flow bottle and the oil injection pump are retained. Pre-mixing for the street is not practical. You would have to pre-mix at 33:1 which is about what the pump does at high RPM's. However the pump is calibrate to lean the engine out at lower RPM's. Pre-mixing would make the bike smoke to much around town, and doesn't add much to the performance. The Transmission is a close ratio racing unit. A little work to take off from a dead stop, but once you get moving, it easy to keep this jewel in the meat of the power band. Yamaha makes a special "AP" dry clutch plate, which is different from the standard dry plates. You have to order them seperately from Yamaha Japan. The raditor is straight off a TZ250 race bike. Same part number. Since the bike is used on the street, little foam filters are used on the carburetors. |
|
