26 - 28 - 30mm. Features: - Piston-type throttle valve - Indipendent starting circuit - Idling system with jet and mixture adjusting screw or air adjusting screw - Main circuit with mechanical mixture adjustment by conical needle - Versions with idle adjusting screw on the left and/or on the right - Bowl. Factory-new Dellorto PHBH 28FD carburetor for the Honda NSR 125. This carburetor is the original equipment on Honda NSR Raiden 125cc, but can be re-jetted to suit any engine. It features a 42 mm plain air intake connection and 36 mm rubber sleeve type engine connection. ![]() SETTING UP - Engine Carbs 2 PART 2 JETTING IN AND SETTING UP CARBURETOR INSTRUCTIONS This follows on from where I have explained how to prepare your engine ready to set up the jetting in procedure. We will cover as many popular carbs that MB have used over the years. If there's a carb not mentioned then the chances are we have not used one so we are not experts to give advice. But ALL carbs work in the same way so a lot of information is relevant and given enough jets you should be able to set up a carb whatever it is. As previously explained, fuel flow is very important from the petrol tank through to the float bowl so the engine can take what fuel it needs at any part of the rev range. FLOAT AND FLOAT BOWLS These are important as they control the amount of fuel which the carb can hold and supply into the engine. Most engines standard or mildly tuned do not need every thing to be fast flow. BUT it is always better to make sure the head of fuel can flow straight into a carb to prevent fuel starvation which can and does happen from engine to engine. AMAL Amal offer 3 float bowls; each has its own needle valve • 1.6mm needle valve hole is for engines fitted with a fuel pump • 3.2mm needle valve hole is standard with fuel fed by a petrol tank • 4.0mm needle valve hole is for alcohol fed engines Amal offer two floats • Standard (large) fitted to all 28 – 34mm carbs • Shallow (small) fitted to all 22 – 26mm carbs. Use the small float in all high revving engines DELLORTO Dellorto offer a number of float needle valves • • 2.25 • • 2.75 • • • 4.00 The smaller is fitted to low revving motors, the larger to higher revving engines, changing them controls either fuel starvation or flooding • PHBL 22- 26mm use 2.00 - 2.50mm • PHBH 28 - 30mm use 2.50 - 3.00mm • VHSA/B should use 3.00 - 3.50mm Dellorto offer a number of float sizes, shapes and weights, usually standard works fine. Dellorto offer a various types of float bowls • PHBL/PHBH are usually standard, plastic or alloy (there is no difference) • VHSA/VHSB have varying sizes use the larger type to hold the most fuel A word of warning! We have found that all flat slide Dellortos have a fault from the factory and require what we call a blue print modification. None converted carbs will get fuel starvation below 3/4 of a tank, (mainly on fast high revving engines). A word of warning! Using an Amal power-jetted carb on a TS1 engine could result in fuel starvation at high rpm as the carb is at an angle and where the Power Jet is would suck air! Convert the carb to a none power jet type. PWK Type carbs, Kiehin, BGM, Stage6, OKO, Koso The down side of the PWK type of carbs is the fuel flow is slow, these are excellent on mild or low revving engines and usually work fine. But on a TS1 or high revving or powerful engine the engine can need more fuel than the carb can give! Harlem diary of a summer raritan. PWK's don't have removable float needle valves or smaller floats or larger float bowls as does the other carbs mentioned. Fuel flow can be adjusted by bending the float arm, we see this tip on forum threads but only helps the problem.
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