Step-By-Step Yamaha XS650 Engine Overhaul Instructions

Yamaha XS650 Engine Overhaul

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Lorenzo’s Yamaha XS650 has languished unwanted and neglected in a damp cellar for just over five years. Once used as regular daily transport, the bike went sick during one daily commute and had to be recovered by the RAC. Despite several weekends tinkering Lorenzo was unable to diagnose or fix the problem, and eventually resorted to alternative transport. As weeks turned into months the bike began to disappear under the inevitable piles of old carpet and cardboard boxes that accumulate in cellars everywhere, and fixing it slipped off the agenda. Over the years the bike has cropped up in occasional conversation until eventually I spent a Saturday morning helping Lorenzo dig it out with an eye to putting it back on the road.

A late model SE (originally badged “US Custom” on our shores), the bike was looking rather sorry with advanced furry mold creeping across the alloy, scratched and oxidised paintwork and the expected seized calipers and flat tyres. The exhaust had seen better days too, though encouragingly the engine turned over on the kickstart and even showed some signs of compression. After several cups of tea and careful weighing of the piggy bank Lorenzo decided to opt for exploratory engine surgery to see if life could be breathed back into the bike. And so it was that after much heaving and dragging, we eventually manhandled the bike onto my workbench and the stripdown commenced.

Part 1 – Stripping Down the Engine

1. This looks like a challenge. We’ve decided to strip the engine completely and see what we find, though after standing for so long I anticipate spending some time with seized bolts and sheared off studs. The fuel tank and side panels come away easily, and I’m surprised to find the exhaust unbolts from the cylinder head without problems. Yamaha used big 10mm studs and dome nuts for the exhaust headers, so even after years of corrosion a good heave on a spanner slackens them off without shearing. So far so good. At this point I remove the sump drain screws and let the engine oil drain as work continues.

2. Removing the carbs on these bikes can be quite tricky as there is very little room between the rear of the cylinder head and the frame. I started by removing the air filters to make as much space as possible.

3. Even with the filters removed there’s insufficient space to pull the carbs off, and I found it easiest to unbolt one of the inlet rubbers first. The carbs can then be waggled clear as an assembly, leaving one inlet rubber on the head. I unhooked the throttle and choke cables, then laid the carbs aside for attention later. The heavy smell of stale fuel confirms that the carbs will have to be completely stripped and rebuilt before we can even think of starting the engine later on.

4. Next, the upper engine mountings. The head steady brackets themselves are quite heavily rusted but with a little persuasion all the bolts eventually come free without shearing. All bikes will suffer from some cosmetic corrosion in this area under the tank, as condensation accumulates here when the engine is warming up.

5. At the front of the engine this large diameter oil feed pipe runs upwards from the crankcase and branches into two seperate feeds for the rocker gear. A gland nut secures the pipe onto an adaptor screwed into the crankcase, and first attempts at unscrewing the pipe resulted in the adaptor loosening off with the gland nut securely rusted to it. Eventually I managed to use two 22mm open ended spanners to free it off, but it’s easy to damage the pipe in the process.

6. I continued the strip by removing the ignition components from each side of the head. The XS650 design is unique in that it carries the points on one side of the engine and the auto advance unit on the other, a shaft running through the centre of the hollow camshaft to link the two together. I marked the points backplate with a screwdriver before removal so I can replace it in the same position later on.

7. On the other side of the head the auto advance unit needs to be carefully dismantled for removal from the crossover shaft. A large flat sleeve nut holds the auto advance backplate in place, once unscrewed the crossover shaft can be slid out of the camshaft and stored away. This whole mechanism may look complex at first glance but it’s actually quite straightforward to work on, albeit a bit fiddly.

8. With the points assembly, auto advance and crossover shaft removed the two housings can be removed from each side of the head. Each housing carries an oil seal which runs on the camshaft itself. These oil seals will be replaced during the rebuild along with the gaskets and “O” rings which seal the housings against the cylinder head.

9. I’m not going to disturb the rest of the top end until the engine is out of the bike and on the workbench, so at this stage I turn my attention to the side covers. The more I dismantle, the lighter the engine will be when I come to lift it out of the frame. On the left side the engine cover lifts away to reveal the generator unit and drive sprocket. The generator stator is retained in place with two long phillips screws, with these removed and the electrical connector unplugged the stator can be lifted away and carefully stored. I’ll leave the drive chain on the gearbox sprocket at this stage as it will allow me to lock the engine with the rear brake, useful when unfastening the clutch centre nut and primary drive gear.

10. On the engines right side now, the first step is to remove the oil filter cover and filter. The filter is a washable gauze type and can be cleaned in paraffin and dried off with compressed air before refitting later. The brake pedal and right hand footrest come off next, which allows room to remove all the screws and lift the cover away. I had to give the front of the cover a couple of light taps with a hammer to break the gasket seal. The tacho cable should also be disconnected at this stage.

11. Removing the right hand cover reveals the clutch and primary drive assembly. Unusually the XS650 engine carries its oil pump mounted inside the engine cover, driven off a gear from the primary drive. This gear also drives the tacho cable. I’ll take a close look at the oil pump later. The clutch assembly will have to be removed to gain access to the gear selector mechanism behind it.

12. With the clutch springs, pressure plate and friction plates removed the whole clutch assembly is held on the end of the input shaft with a single nut retained with a locktab. This nut is tight, and some means of stopping the clutch drum from rotating is useful whilst undoing it. Not for the first time I’m resorting to my trusty Kawasaki service tool, a rather crude device fabricated from two steel claws welded onto a pair of Mole grips. Not a difficult thing to copy if you wanted to make your own. Alternatively a couple of old clutch plates could be drilled and bolted together, effectively allowing you to lock the inner and outer drums together. A foot on the rear brake pedal with the bike in gear should then hold everything steady.

13. With the clutch removed the kickstarter mechanism can be lifted away, giving full access to the gear selector. The selector claw unhooks from the end of the drum and then slides out of the crankcase. Watch for the small springs that hold it in contact with the drum. Now is a good time to remove the detent roller and spring that clicks the selector drum into position. Watch also for any shims and washers on the input shaft, these will need to re-fitted in the same order during the rebuild.

14. Releasing this nut from the end of the crankshaft permits removal of the primary drive and oil pump drive gears, which should simply slide off. The primary drive gear is located onto the crank with a woodruffe key, collect it and store it safely for later.

15. The starter bendix assembly can now be released and lifted off its shaft. On the XS650 the starter motor is bolted underneath the rear of the crankcase and drive is transmitted to the bendix by a crossover shaft, seen here just to the left of the bendix. The crossover shaft has a splined gear at each end which simply push on to the shaft, the whole thing being located by the small catch plate and single screw seen here. Be careful if you’re not intending to strip the engine completely; if you remove the catch plate and slide out the crossover shaft it will be almost impossible to slide it back into engagement.

16. Now at last I’m ready to remove the engine from the frame. First I make final check round the bike to make sure I’ve disconnected all electrical connections and control cables. Surprisingly all the engine bolts loosened off without too much trouble, and with the engine plates removed the engine lifts up and clear from the right side of the frame. I was working alone at this point but the assistance of another pair of hands is always useful when lifting an engine out.

17. With the engine supported on the workbench I can now proceed to strip the top end. Firstly the cam cover unbolts and lifts clear, revealing the single overhead cam and two-valve-per-cylinder engine layout. The cam followers remain captive in the cover, at this stage I’ll put the whole assembly aside for examination later. The outer four cylinder head nuts sit atop rubber washers, these need to be replaced on the same studs on re-assembly to prevent oil leaks.

18. According to my workshop manuals it is necessary to split the camchain at this stage, and rivet it up again during re-assembly. I have an aversion to riveting camchains, preferring to use an endless chain when possible, so I decided to see how far I could strip the engine without splitting the camchain. The camshaft is supported on two pairs of hefty roller bearings, one pair at each side, and with the camchain tensioner removed there’s enough slack in the chain to slide the bearings off the ends of the camshaft. With the bearings clear the camchain easily unhooks from the cam drive sprocket, and the camshaft can be lifted free.

19. Now the remaining three small bolts holding the head to the barrels can be removed, and the cylinder head lifted clear. Note the big screwdriver I’ve slid into place to stop the camchain dropping into the crankcase as I lift the head clear.

20. Removing the barrels is simply a matter of sliding them upwards and off the pistons. Be careful as the pistons emerge as they can rattle against the crankcase mouth. Again the camchain will need something to stop it falling into the crankcase. I’ve tied a piece of electrical wire around it and hooked the wire around a casing screw while I lift the barrels clear.

21. Now I can remove the pistons. Delicate work with a set of small pliers gets the circlips out, and the gudgeon pins slide out to release the pistons from their respective small ends. I always discard old piston circlips to avoid the temptation of re-using them, and I’ve marked each piston by scribing “L” or “R” inside the skirt to make sure they go back on the same rods on re-assembly. If in doubt it’s also worth scribing a mark to indicate the front of each piston, though on this engine I’ve already noticed Yamaha have cast direction arrows on top of the piston crowns.

22. The rear camchain slipper blade is fixed into the top of the crankcase mouth with four phillips head screws which can now be released. And here I finally discover why it’s necessary to split the camchain to totally strip one of these engines; the camchain loops around a small tubular brace on the slipper blade mounting. However I have learned that it’s possible to strip the engine’s top end with splitting the camchain, which should save a few headaches if you just want to do a rebore or valve grinding job.

23. Turning the engine over now, I can remove the bolts which retain the sump and lift it clear. The sump filter is a gauze strainer which can be cleaned off in paraffin and dried off. A small magnetic plate is bonded along the gauze and will also need careful cleaning before re-fitting.

24. A quick check round to make sure I’ve removed all the ancillaries and it’s time to split the cases. Like all Japanese engines, there are crankcase retaining bolts fitted from both the top and the bottom half, and it’s important to find them all and remove them before tapping the cases apart with a rubber mallet. With the joint split, the lower casing just lifts away and leaves the crankshaft and gearbox shafts in the upper casing.

25. And finally the crank and gear shafts lift out. Just to prove a point I’ve left the camchain in place while I lift out the crankshaft. So it’s even possible to remove the crank without splitting the camchain, should you so desire.

Part 2 – Sorting out the Bits

Last update I stripped Lorenzo’s 1979 XS650 engine down for exploratory surgery. The bike had proved troublesome on the daily commute, and had been relegated to the back of a damp cellar for almost five years, neglected and forgotten. Despite the ravages of time the engine proved fairly straightforward to dismantle, and I can now turn my attention to examining the internals to see what parts need attention before the rebuild.

1. With the cylinder head off the combustion chambers show signs of heavy carbon deposits, particularly on the left cylinder. This looks dry rather than oily, and leads me to wonder if the bike had been running too rich. Before cleaning up the combustion chambers I’ll take a closer look at the pistons.

2. The piston crowns also have heavy carbon deposits, but otherwise look in fairly good shape. A few minutes work with some steel wool and Solvol Autosol reveals shiny alloy beneath. The pistons are standard, indicating that the bike has not yet been re-bored. This gives plenty of scope for re-conditioning if required.

3. The ring gap measurements are well within factory tolerances. I always measure the gaps at both the top and the bottom of the stroke. No wear ever occurs at the bottom of the cylinder bore, so an excessive gap here gives a measure of piston ring wear. Any wear on the bore itself will be at the top of the stroke; if the ring gap is appreciably larger here a re-bore might be necessary to recondition the bores. These simple measurements give a quick and accurate indication of both bore and ring condition.

4. Satisfied that the bores and piston rings are serviceable, I can now turn my attention to the valve gear. Each valve is retained in place by two split collets engaged into the top valve spring collar. A valve spring compressor is needed to compress each spring far enough to remove the collets, then the springs can be lifted off and the valves slid downwards out of their guides.

5. Once again, evidence of heavy carbon deposits. The backs of all four valves need a good cleaning up with a rotary wire brush before proceeding. The inlet valve on the left has still to be cleaned off, the one on the right has been cleaned up. Carbon build up like this won’t significantly affect the running of the engine, but does nothing to help gas flow and should be removed while the valves are out.

6. The valves need to have a good compression seal in the cylinder head. After many thousands of miles the valve sealing surface, indicated here, will begin to develop small pits as the metal suffers from constant wear and heat. Running the engine with incorrect valve clearances will also contribute to rapid valve pitting.

7. The valve seats in the cylinder head suffer in exactly the same way. With the combustion chambers cleaned up some pitting is evident in the seats. This is the area to watch carefully on older engines designed to be run on leaded fuel. Modern unleaded petrols do not have the additives required to protect these vulnerable areas, and a professional unleaded conversion will include the fitting of new valve seats and new valves made from higher grade hardened steel.

8. In my experience most Japanese engines, even quite old designs, will cope quite happily with unleaded petrol. However the hardened steels are tough to re-condition by hand, and traditional valve grinding methods don’t usually make much of an impression on them. Before sending the head out for re-conditioning I decide to try the traditional method of valve grinding using a wooden stick fitted with a rubber sucker. With a little grinding paste smeared on the valve seat I can then rotate the valve by hand, lapping the valve head into its seat.

9. Lo and behold the traditional method works a treat, producing a splendid matt grey ring around the valve head and its matching seat. Two or three applications of grinding paste are sufficient to remove all traces of pitting, and I can finish off by carefully washing the valves and seats with petrol. However the ease with which I lapped in these valves makes me suspicious of running this engine on unleaded fuel, and I’ll be recommending Lorenzo uses a fuel additive like Wynns Valve Guard when running the rebuilt engine.

10. The XS650 follows a traditional SOHC design and has four rocker arms held captive in the rocker cover. With the large diameter chromed plug removed the rocker pivot pin should simply slide out and allow the rocker to pull free. In practise the pivot pins are quite a tight fit in the rocker cover, but Yamaha have thoughtfully drilled and tapped each one so that an M6 screw can be wound in to help remove it. I found that by packing washers against the side of the casing I could progressively wind an M6 allen screw into each pin to withdraw it.

11. The rocker arms have the valve clearance adjuster at one end and the cam follower at the other. Each follower rides over its respective cam lobe whilst the engine is running, and is susceptible to wear, particularly if oil changes have been missed. Some slight scuffing is evident here but doesn’t warrant the price of fitting a replacement. Heavy wear would mean replacement, and possibly a new camshaft to boot. Check the valve clearance adjusters too, these are prone to pitting on the XS650 motor and might need to be replaced.

12. To remove the ravages of corrosion and years of baked on dirt we have opted to have the head, rocker cover and barrels bead blasted. This is a specialist job and needs to be done with care. It’s all to easy to get tiny amounts of grit into engine oilways, leading to horrors once the rebuilt engine is started up. I entrusted the parts to Paul Coward at Bikerworld, who once again carefully masked up all the vulnerable surfaces before producing a splendid finish. The next step is to thoroughly wash the parts in paraffin and blast everything clean and dry with a compressed air jet. To make doubly sure everything is spotlessly clean I then pop the bits in the dishwasher, making sure the wife is well out of the way first!

13. Before the valves go back in these valve stem seals need to be replaced. They just pop over the tops of the guides, and serve to stop excess oil running down the guides which would cause the engine to smoke on the over-run. Replace them every time they are disturbed.

14. Now the valves can be re-fitted in their original positions. The valve spring compressor allows me to hold the valve springs down whilst popping the split collets into place on the valve stem. A smear of grease holds them in place while I unwind the compressor and remove it. Don’t forget the steel washers under the valve springs.

15. For purely cosmetic reasons I’ve cleaned up the crankcases and given them a coat of silver engine enamel. I’m reluctant to opt for bead blasting on such complex castings due to the risk of getting grit into the oilways. An hour spent with paraffin and steel wool before another application of the dishwasher gives a good enough surface to take the paint. Inside the top crankcase I noticed the legend “Paul 1991” scratched into the alloy, evidence of a previous re-build. I’ve now scratched “Rod 2002” alongside it!

16. Last month I commented that the engine can be stripped without splitting the camchain, and here’s the evidence! Unfortunately the chain does loop around the rear slipper blade mount, so will have to be split if it is being replaced. The “soft link” can be easily found as then end plate is a lighter colour.

17. The front slipper blade is mounted into the barrels and retained by two M6 screws. On this engine the rubber face has become separated from the alloy blade and will have to be replaced. Apparently this is not an uncommon problem on XS650s and is worth checking at every top end strip.

18. The oil pump follows conventional Japanese design and consists of two concentric rotors running in a carefully machined housing. Unusually the XS650 oil pump lives inside the clutch cover, and the tacho drive will have to be removed first to access it. Check carefully for score marks in the housing and rotor faces, but if any damage is evident the clutch case itself may have to be replaced.

19. While the tacho drive is apart check for this tiny oil seal which stops engine oil escaping and leaking out from the tacho cable. The threaded part of the cable mount screws out and the oil seal presses into the housing beneath it.

20. The gear cluster shouldn’t usually give much trouble, but older XS650’s can sometimes develop a fondness for jumping out of gear. Careful inspection of these dogs should reveal any problems, rounding or wear on the pins indicating a problem. I don’t normally strip gears from their shafts unless strictly necessary, but if replacing a single gear cog support the gear shaft upright in a vice and carefully remove each gear, circlip and washer before replacing in the same sequence.

21. Any gear selector problems can usually be traced to the selector forks. Watch for excessive wear or signs of blueing due to excess heat on the fork tips here. Bent selector forks will fail to engage the gears correctly and should be replaced.

22. The kickstarter mechanism is a pretty sturdy affair and is unlikely to give problems, though this is a good time to replace the return spring if it has been showing signs of weakness. The drive gear shows signs of polishing on the teeth but this doesn’t look excessive.

23. The starter bendix gear looks to have had a rather harder life, and is showing signs of wear on the edges of the teeth which engage with the crankshaft. However looks can be deceptive; the gear teeth are actually relieved as part of the manufacturing process to help the starter engage. Though some wear is evident I consider this gear still serviceable, and we’ll be re-using it.

24. The old sump filter (right) proved to have a piece of gauze missing. Not only was this not filtering the oil as it should, it also makes me wonder what happened to the missing piece! However as no signs of foreign bodies were evident in the engine I’ll simply replace it with a new one (left).

25. Final thing to check before the rebuild are these two carbon brushes which fit onto the alternator stator and bear against two copper tracks on the rotor. Excessive wear on these brushes is a common cause of charging problems on these bikes, and is easy to overlook. These are about half worn, and should be good for a lot more miles.

And that’s all the bits sorted out. The engine has proven to be in better condition that we’d expected, and I’m wondering if Lorenzo’s original problem was down to a carburation fault as evidenced by the excessive carbon deposits in the top end. Reconditioning the valves should help it to run better, and we’ve decided to replace the camchain as a precaution while it’s being rebuilt.

Next month I’ll be clearing the workbench and bolting it all back together. Thanks to Paul Coward at Bikerworld (tel 01422 844681 or 07944 698793) for the bead blasting.

Part 3 – Rebuilding the Engine

Lorenzo’s XS650 has proven to be in rather better condition than I’d expected after being stored in a damp cellar for over five years. A full strip of the engine revealed no major problems, only the front camchain slipper blade being urgently in need of replacement. I’ve had the head and barrels bead blasted and we’ve opted to replace the camchain, so armed with a gasket set and a full set of replacement oil seals I’m now ready to rebuild the engine.

1. The roller bearings fitted to the main and big ends are more or less bulletproof unless a major lubrication failure has occurred. The crank has shown no signs of distress, so I’m happy about re-fitting it. The starter drive gear, indicated, shows some signs of wear but this is not excessive.

2. Before assembling the crankcases I start by re-fitting the starter crossover shaft and it’s drive gears. This can be really difficult to engage later, as I discovered during the engine strip.

3. The gear selectors also need to be assembled into the top crankcase half at this stage. I’ve been careful to keep the three selector forks in order, and can simply slip them over the selector drum as I slide it into the crankcase. Each selector fork then needs its respective pin sliding into place until it engages with the track on the selector drum, then I slide a cotter pin into place and bend the ears over to secure the pin.

4. This cross shaft also serves to locate the three selector forks in the correct position. There’s a fair amount of movement in the selector forks with everything correctly engaged which undoubtedly helps gear selection, but is also probably responsible for the traditional Yamaha “clunky” gearbox.

5. Now I can position the crankshaft and the two gearbox shafts into position in the upper crankcase half. I’ve placed new oil seals on each end of the crank and on the gearbox output shaft at this stage, and made sure the gearbox bearings are engaged with their respective locating rings in the crankcase. I’m fitting a new camchain too, so I’ve hooked it around the crankshaft before proceeding.

6. After applying a thin smear of Blue Hylomar to the jointing faces I can now fit the crankcase halves together and refit and tighten the bolts. The workshop manual gives a tightening sequence, but if in doubt I always tighten the bolts in a diagonal pattern working from the centre of the engine outwards. Make sure the shafts rotate easily in their bearings before proceeding. The starter motor fits underneath the XS650 engine, so I re-fit it now to save problems later. The starter reduction gears can then be fitted as an assembly to the left side of the crankcase.

7. Turning the engine right way up, I can now lower the barrels into place after greasing and fitting a new base gasket and “O” rings. Many people like to use ring compressors for this job, but I prefer to gently ease each ring into the freshly oiled bore with the aid of a small screwdriver. Once all the rings are engaged the barrels should tap gently home with a rubber mallet.

8. With the barrels seated on the crankcase mouth I can fit the new front slipper blade into position and bolt it up with the two M6 bolts. The cylinder head then simply slides into place over the studs, having first made sure all dowels are in place, and I’m ready to re-fit the camshaft.

9. As with all engines, the valve timing needs to be spot on and it’s worth taking time to check and double check the timing before progressing. I’ve started by temporarily re-fitting the generator stator which allows me to accurately line up the “T” mark, ensuring the engine is at TDC.

10. The camshaft now drops into place in the head, and I’ve rotated it to line up this punchmark with the cylinder head flange. This will index the timing correctly. The new camchain is wrapped around the sprocket and temporarily retained with a loop of electrical wire to stop it dropping into the engine while I double check the timing marks.

11. Riveting up the soft link into the new camchain is a delicate job as it’s easy to drop the link or its end plate down into the engine. It’s possible to buy a special tool for riveting up the link but I’ve always got satisfactory results using a nut splitter like this.

12. With the camchain tensioner re-fitted to the rear of the cylinder block I can now tension up the chain. On this design the threaded sleeve winds down around the plunger until the plunger end is flush with the housing. This correctly pre-loads the tensioner spring. The new camchain was quite a tight fit, so I’ve set the tensioner up with almost zero pre-load for the time being. It will need checking once the engine has run.

13. Next, the rocker cover. I’ve already re-fitted the rocker arms, but these four sleeves need to be pressed into place with new O rings before fitting the cover. The sleeves and O rings will prevent oil leaking out past the head bolts. A thin smear of Blue Hylomar will seal the rocker cover to the cylinder head.

14. This is a convenient time to set the valve clearances. These could close up slightly once the engine has started up, so I’m setting them slightly wide. I’ll be re-checking them once the bike has run after the rebuild.

15. All that’s left to assemble on the top end is the ignition components. With the points and auto-advance housings re-fitted to the head with new gaskets and oil seals, I can lightly grease the crossover shaft and slide it through the camshaft.

16. The auto-advance unit fits onto the right hand side of the crossover shaft. The easiest way to fit it is to locate the baseplate first and clamp it up with its locknut. The centre boss then slides into place before engaging the bobweights and tightening the centre nut. Each bobweight is retained by a tiny circlip which needs to be carefully clipped into place.

17. On the other side of the head I can now re-fit the points backplate. Before removing it I took the precaution of scribing a reference mark on the housing face. Now I can simply line up my reference marks and clamp up the screws. I’ll be checking the ignition timing with a strobe once the engine is running to make sure its spot on.

18. Now for the clutch and primary drive. I’ve opted to start by sliding the starter bendix assembly onto its shaft. The whole starter clutch mechanism is unusual on the XS650, the starter motor drives a set of reduction gears on the left side just beneath the gearbox sprocket. Drive is then transferred to this bendix assembly via a crossover shaft. A rather convoluted system which suggests that the electric starter was adapted to fit an engine originally designed for a kickstarter only.

19. Next I’m refitting the detent roller to the end of the gear selector drum. This clicks the selectors into their correct position when changing gear. Make sure the return spring is in good condition and correctly engaged.

20. The gear selector shaft can now be fitted. The shaft slides right though the crankcase, the selector claw engaging with the pins on the end of the selector drum. I’ve taken the precaution of fitting a new gear shaft oil seal into the left side of the crankcase first.

21. With the gear selectors in place the clutch can be rebuilt onto the input shaft. A washer and spacer slides onto the shaft first, followed by the clutch basket and inner drum. I’ve used a new locktab on the clutch centre nut to make sure it can’t loosen off later. Before the clutch plates go back in I’ve done a quick check for worn or buckled plates. Then with the clutch pressure plate fitted the primary drive and oil pump drive gears can be re-fitted to the crankshaft.

22. The oil pump assembles into the inside of the outer clutch casing. I’m taking the precaution of priming the pump with lots of fresh engine oil to give the lubrication system a hand when the engine is started for the first time.

23. After refitting the oil pump drive gear the tacho drive shaft slides downwards into the clutch casing to engage with its worm drive. The tacho drive boss, with a new oil seal fitted, slides over the shaft and into place in the casing, and is then secured with its lock screw.

24. After greasing and fitting a new gasket the clutch case then goes back on the right hand side of the motor.

25. Finally, before re-fitting the engine in the frame, this rubber faced guide plate clamps in place around the gearchange shaft. This not only protects the shaft itself, it also stops the drive chain cutting into the alternator wiring. The rubber facing on this guide plate is quite heavily worn but is still serviceable.

With the engine re-built we’re now ready to fit the engine back in to the frame. However Lorenzo, the bikes owner, has been so pleased with the condition of his engine the he’s now considering a full restoration to take the bike back to its former glory. The next step is to get the frame powder coated, then we’ll be looking at some re-chroming and new paint as funds become available. I’ve a feeling this could turn into an extended project, so I’ll keep you posted on developments as work proceeds. In the meantime the engine will be kept safe, dry and warm in Lorenzo’s living room.

Thanks to Granby Motors of Ilkeston (tel 0115 944 1346) for their help with gaskets and spare parts for the re-build.