Kawasaki KX250F Factory Tuning And Fuel Injection to keep expert riders at the front of the pack

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Filed Under (Kawasaki) by admin on 08-02-2011

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Battery-less fuel injection system Designed specifically for motocrossers, the fuel injection system incorporates a small lightweight ECU and operates without a battery to further eliminate unnecessary weight. And of course, fuel injection eliminates the need to adjust engine settings to suit track and climate conditions. Ensuring quick starting without a battery was a prime directive when developing this fuel injection system. Using only electricity generated by the kick starter, the engine can be started with only three rotations of the crankshaft. The system delivers electricity in the following order:1) ECU, 2) fuel pump, 3) injector. With a warm engine, starting can be accomplished in a single kick. The compact, lightweight ECU, located just in front of the steering head (behind the number plate), was designed specifically for motocross use. To help cope with the shocks and vibrations of motocross riding, the fuel pump relay is built into the ECU. A 43 mm throttle body makes use of a progressive throttle link to deliver airflow in much the same way as would a FCR carburettor. Using two linked shafts, the throttle body opens more quickly after the 3/8 open position, delivering sharp response and excellent power. Lightweight throttle body is approximately half the weight of a FCR carburettor – a weight savings of about 600 g. To ensure the high-rpm engine’s demand for a high flow of fuel in a short period is met, the KX250F’s injector features larger holes than that used on the KX450F. A fine atomising injector with 4 holes disperses spray particles with a droplet size of 120 µm. Fuel flow is about 20% greater than on the KX450F. The newly designed fuel pump, located in the fuel tank, is a lightweight aluminium construction. (Fuel tank capacity is now 7.2 litres.)

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Triumph Bonneville Tuning Manual

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Filed Under (Triumph) by admin on 20-11-2010

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1. The Float The float bowl acts as a fuel reservoir to meet engine demand. The float is hinged on a pin in the float boss. It rises and falls with the fuel level in the float bowl. The small metal tang integrated in the plastic float supports the float valve, also known as the float needle. As the fuel in the float bowl rises, the float valve is pushed into the valve seat, until it’s high enough to shut off the fuel flow to the bowl. As fuel is used the level in the bowl drops lowering the float which pulls the float valve from its seat, and fills again. Adjusting the height of the float has a big effect on the mixture as a low or high float level makes it harder or easier for the vacuum to suck fuel into the venturi. Differing float levels cause an imbalance which may be perceived as vibration. 2. The Choke This system is referred to as the choke. But that’s a misnomer. When you pull the choke knob, what you’re doing is retracting a plunger that opens a tube connected to the starter jet, allowing additional fuel to enter the venturi just below the vacuum hose nipple. It supplements the pilot system at start up. 3. The Pilot System The primary purpose of the pilot system is to supply the mixture at idle. It continues to supply fuel throughout the entire throttle range, but after about 1/8 throttle is reached the main system starts to put out more of the total mixture, up to full throttle. By adjusting the idle with the big screw on the left side of the carburettors the position of the butterfly is altered, so exposing one or more of the four small holes that are drilled into the venturi, (leading to the pilot jet) just under the butterfly valve, letting more or less air pass the butterfly. Adjusting the pilot screw that’s under the carburettor varies the amount of air premixing with the fuel before it enters the venturi. 4. The Main System Open the throttle and the cable that’s connected to the butterfly valve turns it from vertical to horizontal, so letting more air through the venturi. This increases the vacuum effect that is transferred up through the vacuum drilling in the slide to the diaphragm valve that leads to the diaphragm chamber. The top chamber is separated from the bottom by a rubber diaphragm. The bottom chamber is open to atmospheric pressure from the airbox. When the vacuum in the top chamber rises enough, the constant ambient pressure of the lower chamber helps the diaphragm valve overcome the downward force of the diaphragm spring, so it rises from the ven- turi. As the diaphragm is raised the needle is pulled out of the needle jet, exposing a thinner portion of the needle taper which allows more fuel to rise into the venturi to meet the increased engine demand. The key parts of the main system are shown in the photo below

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Mikuni HSR 42/ 45 Installation Instructions

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Filed Under (Mikuni) by admin on 31-10-2010

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To install, remove the stock carb per Yamaha shop manual procedures. Remove stock throttle cables. Install Mikuni HSR carb into intake manifold and tighten manifold clamp. Install new HSR series throttle cables and adjust cable slack per Yamaha shop manual procedures. Hook fuel line to HSR carb and fasten clamp.* Start motorcycle and fine tune HSR carb for proper running per supplied Mikuni tuning manual. *NOTE: Mikuni HSR series carburetors are designed for gravity-feed fuel systems. You should bypass your stock fuel pump and directly feed your HSR carb right from the fuel petcock. We have noted, though, that you may not be able to get good fuel flow from your Road Star fuel tank in low-fuel situations. You may run your stock fuel pump with the HSR carb, but to do so requires the purchase and installation of an adjustable fuel pressure regulator (set at ½ to 1 lb. of pressure). These are available from most auto parts stores. The stock carb has 2 wires running to the lower rear of the float bowl , these were for a carb warmer, they are not used in this application. Unplug these wires at the main wire harness and retain with your stock carb. The Road Star ignition system uses data from the stock throttle position sensor (TPS) to manage your ignition timing. It is necessary to give the bike this information. You may do so by removing the TPS sensor from the stock carb, leaving it plugged into the main wire harness (the sensor must be fixed to a closed-throttle position), or you may locate the plug for the TPS on the main wire harness and test the leads – you will find one ground, one with .5V and one with 1.5V. Connect the 1.5V to the ground and this will give the bike the same information as stock fully closed throttle.

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