A 1000cc, 50 degree twin with side-by-side rods on a robust 4 bearing bottom end. With a short pushrod valve train and dual valve guides for stability, though these machines will rev freely, are best known for their thunderous torgue in lower and intermediate rev ranges. As a high performance machine without peer in their day and then later, when the cycle parts well out of fashion, this massive power plant still a very viable basis for a race machine, 60 years later, on anything but a stock/neglected machine, there can be a myriad of ills. These pointers apply to unmolested appearing machines with little/no history for which every precaution must be taken as the power plant is where one can quickly experience the greatest expense and often the most frustration in acquiring the necessary services to restore it to its makers intended level of power, oil tightness and reliability. For a newly acquired or long owned machine never having run properly, it is imperative you make no assumptions and establish a baseline for exactly what you have by closely reviewing every component/component group. It is then that you can prioritize if/what may need attention given your intended use for this machine once running.
  • Crankcase Breather: Cutting to the chase this subject gets more attention than any other with a Vincent. With many locations inviting oil leaks if not tended too - like the compression release boss on the timing cover - lengthy seams along the vertically split crankcase, Vins have a reputation for having a crank venting problem when, paradoxically, they have far more crankcase chamber volume to swept stroke to absorb pulses than nearly every V twin made. The results of using a timing gear driven timed breather used by the likes of HD, for example, do not achieve the same effect because of the plumbing fitted where it exits the cases, namely a poor flowing banjo bolt and restrictive 1/4 inch line exiting down low under the machine. Resorting to a simple front on the front exhaust valve inspection cap with the series D does no better, not only because the restrictive banjo bolt and hose remains, but being open and not timed means the engine must turn around and pump out gases drawn in as the pistons rise to TDC and draw a vacuum on the case.

    Everything from large elephant trunk breathers off the mag drive cover to elaborate valve adjustment cap configurations await your purchase and fitment but a neat inconspicuous solution awaits at Autozone in the form of a partial bleed back positive crankcase pressure valve or PCV. Parial bleed back? Yes, Only of late have Vincent motors achieved close to the sealing of modern engines through o-ring, seal and gasket mod's, thus, a PCV with a complete vacuum seal will begin to effectively draw down crankcase pressure until the engine will attempt to "breathe" through any opening it can find. On original/older engines without benefit of sealed valve guides, this can occur most dissasterously at the exhaust guides which with any oil draining down the stem pulled back resulting in "dry guide". You only want as much positive pressure bled off as is necessary to eliminate the most prominent spot for leaks, and that is the port in the timing cover for your decompressor cable to enter the timing chest. On a healthy engine with minimal blow by, this particular PCV meets that criteria. Inexpensive, I got several with the range at this size from Autozone to find the one just halting leaks from the decomp port. You can then just block off your timed breather at the case, or for more original appearance, leave the banjo bolt/fitting in place with a short section of line and plug the end of that.

    To fit this PCV, cut just the hose retention ring of the nipple off, grip lightly with rubber or other soft material in the jaws of a vice as this housing is rather fragile and thread 1/2 x 20tpi. Be advised, as the wall thickness of the inlet nipple is less than .0025, you are lightly cutting as well as "rolling" the threads through deformation of the nipple itself, thus the reason for using course 20TPI. Though not as accurate as a typical application where the bolt threads making nearly full root contact in the received threaded recepticle, this configuration will impart enough enough thread purchase in the similarly modified cap that there's no risk of it coming adrift as it is further secured by the breather hose. Add some Permatex Grey to the threads to ensure oil tightness. Mark the location on your rear cylinder valve inspection cap (I'd order a repro from John Healey rather than ruining a patina'd  original) firmly tightened into the head where the valve will stand at the inclination illustrated, drill/tap your cap. If it does not come to rest in this position when tightened dress it down with sand paper (while checking for rocker adjuster clearance) till it does. Then route a 3/8" inch line down to exit, mine is anchored to the rear of the right hand foot rest and angled slightly out to the side.

    Be advised, if you don't plumb a short section containing a screen as a moisture trap as I elected to do then you may have some oil drips on the ground when initially parking after slow city/urban riding on a machine with worn rings as that is when your crankcase operates with the greatest pulse differentials enabling oil droplets to navigate the 4 inches of vertical run out of the cap to the point where the hose is routed downward.

  • Heads: Head torque is critical to ensuring you do not deform your heads causing upper/lower valve guide misalignment and combustion gas/oil leaks. On a rebuild, torque to 30ft lbs, let sit overnight for the base gaskets to settle, then torque again. It’s advisable to go through a few heat cycles and torque again. You can perform this without removing the UFM, rather, slacken the retaining nuts while the machine is supported by the motor/trans, obtain a torque multiplication device from Sears along with an 18mm crows foot with 3/8 or 1/2 drive.

    If your machine has sat in poor storage for a long time and exhibits poor overall compression, large variance between cylinders and/or hissing of escaping gasses can be heard through any of the ports when turning the motor over with plugs in, it is likely some of the valves remained off their seats and those seats have corroded or have deposits (best outcome) preventing good valve seal. An engine started with this condition can etch exhaust seats if the valves are held even slightly off of them. It's highly recommended you pull your heads, removing the valve train and at a very minimum lightly fine Scotchbrite your seats and valve heads if no evidence pitting found and both surfaces can be made shiny. Otherwise, if a light session with paste does not removing any pitting, the seats will neat to be cut and valves surfaced. But, in advance of that step you'll want to determine the overall health of your heads and eliminate other possibilities for why you may have poor sealing. You can have the valves binding in the guides from misalignment between upper and lower guides which will also result in lack of perpendicularity between the valve and the seat preventing a good seal or bent valves from a plain over rev or use of cams with excessive lift with inadequate clearance to high compression pistons. Assuming your motor has run at some point in its current configuration, study your pistons closely for any arc profile impressions made by the valve heads.

    First, with the heads disassembled, chuck up your valves in a drill - or preferably drill press - and make sure they are concentric and the valve heads not wobbling. Then clean off the valves and seats as described, view the seats for any sign of the valves only seating partially on the seat perimeter in the form of shiny spots. If not evident coat both with a magic marker, insert the valve and rotate it a few degrees back and forth and remove. Look for shiny spots on your valve stems and/or guide bores which indicates misalignment between the upper/lower guides. A machining error much preferred here to heads deformed from over torqueing or excessive loading as experience with side car pulling, but in either situation if rotating the upper guide in its land in the hopes that it or may have been drilled off center (the lower guide as well) does not reduce binding and/or permitting full valve contact at the seat, you will need the heads professionally redone using a fixture for this particular operation wherein the upper and lower guides are of different bore diameter. Memphis Motorwerks can perform this operation.

    If your valves retain the small ring clips to anchor the keepers in the collars, if unduly spread during removal, not only squeeze them back so they grip the groove in the stem, ensure they are still seated in that groove when the keepers in place as the shock of the valve closing can easily cause them to burst out.


  • Cylinders: In a long stored machine, the rings may have rusted slightly, trapped in the bores or etched perimeter rings in the cylinders. Though these can be freed with Kroil and other concoctions, you'll want to remove your cylinders, ensure the rings not entrapped, possibly remove them and measure end gaps (in access of .020 should be replaced) and check to see what base gaskets fitted. The original gaskets very thin, not compressible and therefore stable, some older reproductions sharing characteristics of timing and primary cover gaskets and should be replaced. You'll also have an opportunity to check for obvious signs of rod bearing issues either in end play or radially. On a run in motor in which rings not replaced, ring re-seating can be established by breaking the glaze in the cylinders with a light application of course ScotchBrite rotated by hand in a criss-cross fashion as would result from using a hone, then, very lightly oil the top/bottom faces of the rings.


  • Oil Pump: Though a screw type and quite capable, this is a very large and circuitous oil system. Running a steel screw in a brass housing it is subject to rapid wear when digesting any metal crumbs on machines not have regular filter changes. If your machine does not return oil within seconds of startup when viewed through the oil filler opening, I’d think about renewing your pump. Some perceived crankcase venting problems/leaks can actually be traced to high oil levels in poorly evacuated cases causing oil laden windage.


  • Oil Feed: The makers thoughtfully provided a check valve and spring at the feed fitting on your UFM so that UFM could quickly be uncoupled from the engine without further leaks. Whatever it takes in the shop, my goal is never to have to wrench roadside - especially for something as major as requiring UFM removal - thus that thoughtful feature is unneeded, an impediment to oil flow and should be removed. As an aside, fit one of the drain bolt equiped banjo bolts where the oil feed goes into the engine cases so that you can verify the line is purged when changing your oil. These can be sourced through John Healey


  • Oil - PreLube: Vincent engines are easily pre-lubed for starting after long storage. The heads/valve train are the last to get oil as they are lube'd with the oil return line to the UFM so are particularly vulnerable on start up. Remove each of side facing rocker inspection covers, squirt oil back at the rocker bearing where the rocker pivots and then let oil run down the pushrods to lube the cups and cam followers. Remove the cap nut (M018 - OP40) on the timing cover and jet (M018 - OP39) and with a small rubber sealing washer pump oil until resistance is felt, let this subside and refit components. Remove the small screw in your quill (MO18 - OP/2) and with sealing washer engaged, pump till resistance felt, let pressure subside and refit components. If you've change your oil filter, remove the banjo bolt (MO18 - A22/1) just below your ATD cover and fill the oil filter cavity. Upon startup, with the oil cap removed, within seconds you should observe oil returning to the tank from a small port at the back of the filler neck, a mere dribble is customary. As some motors prone to wet sumping, you will need to operate your machine several minutes to ensure the "real" oil level in the tank is achieved - just above the rectangular cross bar viewed through the filler - before making adding any oil.


  • Oils General: Everyone has a favorite, the guideline here is multi-weight (20-50 or thereabouts) over straight and presence of the additive ZDDP or suitable replacement to protect running surfaces experiencing sheer for which the Vincent is an excellent example utilizing flat cam followers bearing on the lobes of the cams with rather high valve spring rates. The determined ZZDP content threshold for protection on flat tappet motors is .12%, as of 2009, synthetic oil mfr's had dropped this additive to only .07% and some had elected to use a less costly replacement. Though gas engine oil formulations have essentially eliminated it, non-catalytic converter operated machinery (diesel) have retained it and for a time the most readily available was Shell Rotella T. As of 2010, divining their increasingly cryptic spec sheets to determine if it's still present has become difficult. Classic car suppliers and some auto parts stores sell it separately as an additive.


  • Oils Leaks: Until you are confident your crankcase breathing arrangement is thoroughly addressed, you cannot accurately determine the state of your engine's oil tightness. That aside, the principle source for oil leaks on an other wise sealed engine is at the de-compressor fitting in the timing cover, click here and scan down to De-Compressor Setup on guidance to rectify. Other sources are as follows.

    Crankcase Breather Pipe (stock location): As it goes from a port not even at the top of the compartment containing your lower and then exits immediately downward, there is not chance for the pipe's inner surface to utilizing surface tension of liquid to capture oil droplets and then have them able to be drained back in the case as would be with an elephant trunk, standard D configuration or mod like my PCV arrangement. Thus, you will have drips here, most notably in slow speed urban stop/go riding where crankcase pressure differentials are highest and able to project oil laden vapor more vigorously to this pipe.

    Top Oil feeds - Rockers (compression fittings): Unlike most compression fittings using malleable material for both mating surfaces, these (MO18 - A45AS) utilize only one and maybe none on some aftermarket component where both are steel and will not deform to effect a seal when tightened. Excessive tightening only serves to fracture the gland nut thus ruining them. If careful bending of both pieces to get better engaged alignment does not create a perimeter seal when checking the mated surfaces marked with a black pen, then dress down the male insert with fine sandpaper (and clean thoroughly) till full contact made. If this impossible then a seal can be effected by inserting a small rubber o-ring the diameter of the inner perimeter of the gland nut. As there is nearly no pressure being managed in this line, merely cinch up this assembly, do not over tighten.

    Cylinder Base Gaskets Oil can leak at the joint between the cylinders and the engine cases either from crankcase venting issues or from oil intend to lube either piston skirt from ports within the cylinder/liner walls. As outlined in the Heads section above, these will need to be changed as a precaution regardless.

    Oil filter Nut As this is retained by very fine threads, never a good idea to tighten excessively, rather, coat the last few outside threads on a thoroughly de-oiled nut and bore with Grey Permatex, tighten then blow dry with a hair dryer. I use a 1.75 inch (44MM) 3/4 drive  socket (with 1/2 drive adapter) sourced from NAPA instead of the intended K1 for better purchase on this nut.

    Oil Feed/Return Banjos (at engine): The feed (MO18 - A66AS) and return line (MO18 - A58AS) banjos have sealing rings on both sides of the fitting faces against the bolt (MO18 - A22) and the engine case. If fiber, these should be replaced with John Healey's aluminum washers containing a rubber o-ring with the perimeters. As mentioned above under Banjo Fittings (Oil Feed/Return), many reproduction pipes are not of the correct inner diameter, especially the straight bored ones as sighted and are occassionally too large, the o-ring not make contact thus that benefit lost. John H and the VOC Spares sell the proper piping.

    Generator Drive Though your generator sprocket fitted with an oil deflector (MO14 - PD28) on its backside facing this opening (confirm presence), as essentially a slinger, it is not entirely effective as vapor can still exit and on poor vented machines, lots of it as they tend to breathe through drive side crankcase into the primary and then exit at this point. Packing between the face of the generator sealing the taper into the opening is required and that seal is best provided by the petroleum high temp resistant black tar like tape used to insulate automotive air conditioning condenser lines (available at NAPA). Before removing your generator, precisely measure the gap between the face of its drive end and the backside of your engine case, this distance represent the centralized position for your generator to mesh the sprocket correctly within the primary chain run in which it meshes. Warm it the packing material by gneeding it with your hands, make an o-ring, affix to the face of your generator, place it in the cradle and lightly press it into position. Viewed through the generator access port in your primary, the seal should conform to the perimeter of the drive opening without and well on the bottom where warm oil could collect and eventually work its way out. Re-affix your sprocket and adjust.

    Clutch Cover If you find oil leaking here it is either originating from the main seal (MO32 - PD26) on your inner primary of migrating down your transmission main shaft past the (MO14 - PD25) seal which is the harder of the two to rectify. If you have a modern type clutch (Ducati based V2 for example) this is not an issue but can be one with the stock clutch, the one of the two, the pilot clutch (MOO2 - C24) the most noticeably impacted.

    Final Drive Sprocket Though not as common nor prone to occur on machines ridden in predominantly in high gear where the output shaft and transmission main shaft turn at the same rpm reducing seal wear, a leak can originate from here and manifest itself and dark greasy splotches on the right side rear rim or as oil laden strakes centrifuging outward on the side of the rear tire. As your trans cover (MO09 - G1/1-2) must be removed along with the contents and the plate thus disturbing your shift adjustment, this issue best left alone if tolerable.

    Engine Cases The big one saved for last. Original cases were sealed with no hardening hylomars which with the advent of modern silicone based sealers from Loctite were dispensed which to the misfortune of some (me - this Shadow) as the original sealants were far less prone to breaching, especially from pressure/vacuum generated in the cases. If you have a leak you cannot source or seem to stem the tide which only goes away while machine is running if my breather mod fitted then your machine is leaking at the joint faces either along the seem itself or within the through-bolt holes where bosses for their castings portrude into the case itself but have much less mated area. If your leaks can be sourced to these then removed the through bolts, clean thoroughly, coat with Permatex grey, retighten and hope for the best. If from the case seem and between oil changes, disconnect your oil feed/drain pipes, drain off the sump, dry the seem thoroughly and run a bead of JB Weld or similar along it. With the understanding that some day when you split the cases, this little bodge will certainly slow down their parting. If you have determined that it is indeed your case seems then you may have some equalizing between your engine and transmissions as the rear wall of the engine case is the front wall of the transmission. As engine oil is less viscous and the pressure originates on the engine side, it's your transmission that will take the brunt. Check your dipstick for discoloration as trans oil never clouds between prescribed change intervals unless you have the misfortune of a bushing breaking up or engine oil being forced into it.


  • Banjo Fittings (Oil Feed/Return): It's advisable to remove banjo bolts from each and confirm you have the banjo fittings with the internal clearances radiused for proper flow. Various reproduction feed/return pipes available over the years have only had these fittings straight drilled to the diameter of the banjo bolt insert from the washer into the fitting which is completely inadequate, especially for machines desiring to run heavier single weight oils. It is highly recommended to replace the oil feed banjo bolt at the engine with one drilled/tapped for a drain screw. Beyond the convenience of draining the UFM without disturbing the banjo bolt on its sealing washers, this screw allows one to purge their feed line following an oil change as oil should be allowed to drain here until all air bubbles removed. Secure the feed bold itself with a wrench before loosening/tightening the drain screw.


  • Idler Gear: Though alloy quieter and capable of high mileage - often impossible to detect this benefit with the din of the rest of the valve train clattering away - it is prone to shed teeth if not factory original and/or poorly adjusted, installing a steel Lightening type is recommended, but alas, it’s diameter may not be identical to your previous one requiring a half time pinion change to a different size. Be sure you have them on hand before undertaking this change. I have included a PDF download of an article dating to 3/77 from the Chicago section STOP newsletter on how to set one up courtesy of Rip Tragle, a noted Vincent restorer of the 70-90's. Click here to download.


  • Rocker Feed Bolt Conversion: Your rocker feed bolt (MO17 - ET100) acts merely as a stake or pin to locate your rocker bearing (MO17 - ET26/1)in the bore. Though this mod requires pressing out the rocker pin (MO17 - ET28)from the rocker and bearing to insert the retaining nut, for piece of mind, retrofitting a rocker feed bolt that clamps your bearing firmly within the bore not only minimizes shuffling and wear of the bore but reduces noise as well. The pin and rocker (MO17 - ET25) are an interference fit, I would press all of them out beforehand as any that are loose must be re-fitted with over sized pins and the rocker and bearing machined as appropriate. A loose fit leads to the same noise as a loose valve as the rocker not struck in a perfect line so thus offset forces bang the rocker off the side of the bearing. You can purchase this conversion from John Healey at Coventry Spares.


  • Exhaust Nuts: Fine threaded into the ports of alloy heads and prone to damage from improper tightening techniques, over tightening in attempts to settle unmatched header inserts into a stack of washers as distance pieces, you will be fortunate if yours are still usable. A bit more thread purchase can be obtained by grinding the purtruding insert of your nut down till the start of the threads proper with careful dressing of that first thread to ensure a gall-free start. For those good with a vice, one can every so lightly "ovalize" their nut so that there are opposing spots on its threaded length to engage the threads. This deformation should only be about 5 to 10 thou at most.


  • Pushrod Tube Gland Nuts: If your machine has sat any period of time or the prior owner used any non setting sealer in conjunction with the gaskets, it is likely you will not be able to dislodge these nuts with the commonly available tool supplied for the task (MO41 - K1). The ears bend and the slots in your nuts readily damaged as they are only plated brass. Take a small pair of adjustable pliers and grind the ears as depicted to fit firmly in the slots. When freeing the nuts on my motors having sat over 30 years, I securing the handles with a hose clamp so as to enable delivering a light blow with a small rubber hammer much easier. Be advised, non setting sealers may tear the faces of the gaskets and attempt to ball up binding your nuts even after having initially freed them from their seats. The first one or two turns of the nuts are the critical phase.


  • Air Cleaners: If your machine fitted with original carbs you will note in all likelihood no filters or provisions for mounting them present..unless you are most fortunate to have a pair of the exceedingly rare Vokes filters. Original Vincent heads have hardened valve seats fitted to reduce wear from uncleansed induction, so, unless you ride in extremely dusty conditions engine wear is not the primary issue. But carb slide/bore wear is as these carb's design and intake reversion (that small cloud of fuel you see behind your carb bell mouths when backing off on a rev'd engine) cause fuel to coat the working surfaces of the slides where any dust/grit collects to form an abrasive paste. If nothing else, hit your slides with Brake Clean and wipe off this residue regularly. These carbs were designed to run with bell mouths, complete removal to affix flange type filers like K&N's or obscuring part of the trumpet with slip on foam filters will alter air flow/channeling into the venturi area creating flats spots in your rev band, particularly in mid range and up felt as either power tailing off noticeably under acceleration or a tendency for the motor to "hunt" at light steady state throttle openings, especially on engines with aggressive ignition advance settings - you may need to back off a few degrees to mute this effect. Though not an influence at low/part throttle, if your new filters found restrictive, you may also need to step your main jets down and drop the slide needles. To make the filters more unubtrusive, I adapted valve cover breathers grinding out the rubber mounting flanges on the inside where my bell mouths could be accommodated with the important leading edges still exposed to air flow.

    As the only remedy for worn slides/bores which ruin good idle and disrupt throttle roll off from start is sleeving these rare carbs and fitting new slides.  This alone is incentive for some to fit filters as a precaution, so whereas encouraged for high mileage tourers, optional for weekend recreational use. Though not cheap, Steve Hall makes reproductions of the Vokes air cleaners in the U.S. You can email him regarding a set by clicking here.

  • Fasteners (primary, clutch and timing cover): It is not uncommon for the threads to be stripped in the cases at these points, especially the clutch cover. Fortunately, the drillings for these screws were threaded deeper than the lengths of the screws themselves. With a probe, Brake Clean and compressed air, work any grit out of the bores and confirm all are threaded the length of the drillings (if not, get the appropriate tap when ordering form BTF). British Tools & Fasteners not only carries the correct cheese heads in plain steel now, they come in extended lengths. Trim each one individually to suit the bore length.


More info can be found at thevincent.com regarding engines and performing Vincent engine overhauls.



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