Honda MBX125, MTX125, MTX200 Repair Manual 1983-1993

This Haynes repair and service manual covers 1984-1985 Honda MBX125F, 1983-1993 Honda MTX125RW, and 1983-1986 Honda MTX200RW off-road motorcycles.
Book Excerpt: 1983-1993 Honda MBX125, MTX125, MTX200 Repair Manual COOLING SYSTEM

RADIATOR AND RADIATOR CAP: REMOVAL, CLEANING, EXAMINATION AND REFITTING

1. Drain the cooling system as described in Section 2 of this Chapter.
2. On MBX125 models remove its two rear mounting screws and two from mounting nuts and withdraw the belly fairing, then unclip the radiator shroud from it's mountings and release it. Disconnect the expansion tank tube at the radiator filler neck. Disconnect the top and bottom hoses as described in Section 6 of this Chapter. Remove the two bottom mounting bolts and lower the radiator away from its top mounting grommet.
3. On MTX125/200 models disconnect the expansion tank tube at the radiator filler neck and secure the tube end above the tank so that no coolant is spilled. Disconnect the top and bottom hoses as described in Section 6 of this Chapter. Remove the single bolt which retains the radiator guard (its other two mounting screws will have been removed with the radiator mounting bolts (two at the front, one at the rear). Withdraw the radiator.
4. On all models, note carefully the relative positions of the mounting rubbers and the metal washers and spacers before removing the mounting bolts. When the radiator is removed, check the mounting rubbers for perishing or compaction. Replace the rubbers if there is any doubt as to their condition. The radiator may suffer from the effects of vibration if the isolating characteristics of the rubber are reduced.
5. The exterior of the radiator core can be cleaned by blowing from the rear surface forwards with compressed air. Most garages have an air line which can be used for this purpose, but if none is available a garden hose can be substituted, using water instead of air, and a fine-bristled toothbrush. It is essential that all dirt and debris are removed from the radiator matrix as any obstructions to the constant flow of air over its surface will severely reduce the radiator's cooling efficiency. On MTX 125/200 models which are used regularly off-road, great care musts be paid to ensuring that the radiator is washed off at every available opportunity so that mud and dirt is not baked on to the matrix; if this is allowed to happen the radiator will be very difficult to clean.
6. The interior of the radiator can most easily be cleaned while the radiator is in place on the motorcycle, using the flushing procedure described in Section 3 of this Chapter. Additional flushing can be carried out by placing the hose in the filler neck and allowing the water to flow through for about ten minutes; in some cases obstructions can be cleared by placing the hose in the bottom hose stub to reverse the flow through the radiator. Under no circumstances should the hose be connected to the filler neck mechanically as any sudden blockage in the radiator outlet would subject the radiator to the full pressure of the mains supply (about 50 psi). The radiator should not be tested to greater than 14 psi (1.05kg/cm2).

FUEL SYSTEM AND LUBRICATION

ENGINE LUBRICATION SYSTEM: THE BLEEDING PROCEDURE

1. Bleeding must be carried out whenever any part of the system is disturbed, if the oil in the tank has been allowed to drain completely or run dangerously low, or if you have any reason to suspect the presence of air in the system. Air in the system will rapidly produce an airlock which will interrupt the constant supply of oil, resulting in severe engine damage due to the consequent loss of lubrication.
2. The bleeding operation consists of two parts, removing air from the oil tank, the oil tank/oil pump feed line, and from the pump itself, then removing air from the delivery side of the pump and from the oil pump/inlet stub feed line.
3. To complete the first part, thoroughly clean the oil pump and the area of crankcase around it and pack clean rags around the base of the pump. Check that the oil tank is full of oil, topping it up to the base of the filler neck if necessary. Slacken the hexagon-headed bleed screw which is situated on the top of the pump. Oil will flow from the orifice thus exposed. Watch carefully until you can see no more air bubbles in the oil, check that no more bubbles are visible in the transparent feed line, and then replace and tighten down the bleed screw. Remove the rag and clean away the surplus oil.

Subject: 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993 Honda MBX125, MTX125, MTX20 service, maintenance, repair. ISBN-10: 185010901X | ISBN-13: 9781850109013 | Haynes 1132