| This site will tell you how to remove the oil pump mechanism . I am very receptive to comments and suggestions but you use this information at your own risk . Skill Levels explained . Skill Level with engine out : 1. with engine in frame : 2. Personally dirty : 2. Work mess : 1. Tools : 1. Space : 1. You do n't need to remove the engine from the frame . In most of these pictures , Valiant 's engine is removed , but it was out anyway , for other work to be done . All nut and bolt sizes are given as the spanner size required to fit them . Warm the engine and then drain the oil . It is not absolutely essential to remove the radiator , as you can get by with just lifting it out of the way after unbolting it , but really it 's better to remove it . The front casing is much easier to remove if the radiator and fan are not in place . Disconnect the clutch cable at the clutch end . This is secured by two 10mm nuts ; slacken them full off , use a pair of pliers to raise the clutch arm , and slide out the nipple ( at the end of the cable ) from the clutch arm . Remove the 8mm head bolts which attach the front crankcase , and gently pry off the front cover . Do n't use force , and especially do n't use a screwdriver between the mating faces . In the photo ( right ) the clutch cover has been taken off as well , but you need n't do this . The bendy black tube is one of the oil feeds . Carefully remove all traces of the old gasket . Inside the open engine ( left ) . The oil pump itself is hidden behind the large shiny sprocket . This is driven by a chain directly from the crankshaft . Close-up of the crankshaft end , the oil pump drive chain , its sprocket and you can just see the oil pump behind the sprocket . The large outer pinion on the crankshaft is what drives the clutch outer basket . This drives the inner basket and that connects to the gearbox . Remove the bolt which holds on the sprocket , and pull it off with the chain ( left ) . Unbolt the oil pump from the opened crankcase , and pull it off complete with its lower pipe and the metal strainer . Frightening is n't it , what was caught on the strainer ? Having upturned ( left ) the strainer , this is what I found . Tiny bits of metal , plus some slivers of gasket and sealing compound . If you are not replacing the pump , wash off all these bits in paraffin or petrol . The oil pump chain is a continuous one and does not have a split link . If it shows sign of wear , or on reassembly it cannot be correctly tensioned , you should replace it . The CX500 oil pumps are extremely simple in operation and correspondngly reliable ; they often go to 100,000 miles without replacement . They are what 's called trochoidal , which means that they work rather like a heart . An inner star-shaped steel rotor , with four arms , rotates inside an outer rotor with five corresponding cutouts . Oil is pumped between the chambers as the assembly rotates , and goes out into the oil passageways inside the engine . I 'd recommend changing the chain at 40,000 miles but the pump will be good for more than this . If you want to dismantle the pump itself , do so under surgically clean conditions . You can check the internal tolerances if you want to , but you 'll probably need an impact driver to get the holding screws out . If you dismantle the pump , there should not be more than 39/1000ths clearance between the inner and outer rotors , and no more than 138/1000ths between the outer rotor and the body of the pump . On reassembly , note that the punch mark on the outer rotor faces outwards , you should be able to see it during reassembly . Before reassembly , wash or wipe out the oil sump at the bottom of the crankcase area ( left ) . You can see the dipstick poking through in the picture . Any sludge or muck shows neglect in changing the oil and filter . A well maintained engine should be free of all deposits . Reassembly is a simple process . Do n't forget to renew the O-rings around the oil transfer passages . Ensure the 2 hollow dowels are in place ; the one at the top ( right ) and the one between the oil pump body and the front casing . Do n't omit the oil jet and O-ring adjacent to the clutch ( right ) . Finally remember to replace the O-ring directly beneath the oil pump . This feeds into the curly pipe built into the front crankcase cover . To correctly tension the chain , replace the oil pump on its mountings and insert the holding bolts not quite finger tight . Loop the chain over the crankshaft pinion and over the oil pump sprocket and locate the sprocket on the pump . It sits in a shaped slot on the oil pump 's spindle . Insert the sprocket 's locking bolt and tighten it to 6-9 ft lbs . Now wiggle the pump on its mounting bolts so that there is no slack in the chain and tighten the bolts to 6 ft lbs . Check the chain again afterwards . When replacing the front cover , I recommend using a gasket sealant like Hylomar , spread thinly onto both faces , with the actual gasket in between . Insert the 8mm head bolts and tighten finger tight , then in a diagonal sequence to not more than 6 ft lbs - they are easily stripped . Wipe off any excess sealant . Tachometer ( rev counter ) drive CXs sometimes develop an oil smear from the behind the radiator . This weep comes from a failed oil seal on the tachometer casing . It is easily replaced without removing the front cover , but you do need to remove the radiator and fan . You 'll need a new oil seal and tacho casing gasket . The tacho drive assembly is bolted over the front end of the camshaft , directly behind the radiator and directly above the crankshaft . It 's held on with four bolts , and then the assembly can be gently prised off ( left ) . Carefully remove all traces of the old gasket . The leaking seal is the one which fits inside the tacho drive casing , over the end of the camshaft . Poke out the old seal and insert the new one , it goes with its closed end facing outwards , towards the fan . Before refitting the casing , smear a glob of grease over the camshaft 's end . Then fit the new casing gasket , again with a sealant like Hylomar . Tighten the four holding bolts back to 6-9 ft lbs . I recommend changing the oil and filter after 500 miles . |