With unit construction primary runs with cam-actuated damped compensator and clutch baskets fixed in oil bath, primary chain tensioned by flexed blade, and clutch running (presumably) dry in isolated compartment. Click pic here and numbers are referenced in notes below.
- Compensator Sprocket: If your machine feels vibratory under high load or harsh in throttle response, you may have broken or kinked over compensator sprocket springs causing drive slackness with the former. The latter especially can bind the whole mechanism making it operate solid. With that primary off to look at the tensioning blade, folded over springs are readily visible but you’ll need to load the engine on compression with the kicker arm to see how far the cams spread apart to diagnose broken springs as the break may have occurred deeper in the well(s).
If you elect to disassemble this component when re-assembling - if not done previously - install your ring plate (#1) with the smooth side facing the spring ends rather than the side with the wells intended to located them. Though this will increase spring compression reducing dampening marginally, more importantly, it will permit a little shuffle on a machine with worn splines/broaches without capturing the spring ends and folding them over.
- Primary Chain: For the damage a broken one can impart, I'd replace it. At a minimum, inspect for damaged links caused by generator sprocket at improper depth.
- Primary Chain Tensioning Blade: The forward end of the tensioning blade nests via to ears into a cross rod (PD12) that is secured to the adjuster bolt anchored at the lower forward end of the primary. If the chain is permitted to run slack, high deceleration rates under load - like engaging clutch at high speed into too low a gear or bump starting an engine without using the compression release can break off the mounting ears. Primary chains runs in very close proximity to the perimeter of the case and if blade breaks, the chain will wad up most likely at the compensator sprocket end bursting your case. On a newly acquired running machine, for insurance against a possilbe problem, pull the clutch, outer primary and inspect this item (#2).
- Clutch: Volumes have been written on the Vincent clutch but issues as identified by owners generally can be traced to the pilot clutch assembly consisting of the C21 and all components outward in MO02 rather than the more complex main shoe assembly which with a perfect working pilot clutch can be made to operate satisfactorily even if significantly worn out. We'll focus on the pilot clutch as Richardson and Stevens cover the main clutch thoroughly. yours is in good condition, it’s worth having a go, modern alternatives start at $700, but you will need to address/confirm the following. The outer pilot clutch lifts off evenly, if not it will drag, arrange your 6 springs to position tallest/shortest opposite each other or carefully grind the end lands slightly to achieve even heights on all. To reduce offset lift, try to seat the outer adjustment pin on your pressure plate lower and take up the slack with the adjuster at your r/s trans cover keeping in mind it should not be bottomed out against the stop nut because the mechanism will have fouled the inside of the cover limiting movement. . The single Lightening type fibre plate is much prefered over the multi-puck stock pilot. Place your C21 and C23 together to determine if they are flat and rub each thoroughly with course ScotchBrite to break the glaze in a fashion much like cross hatching a cylinder bore with a hone. These two plates should be thoroughly cleaned with BrakeKleen. As it regards the main clutch, if your shoes (MO02 - H30/2) obviously ruined, you can have them religned/replaced with oil-resistant modern bonded linings but be advised the heat used in bonding may damage the fragile plunger springs (ML02 - OP11. Also be sure to camber the leading edges of these shoes as original. More info regarding the the standard Vincent clutch can be found along with some modern replacements here at thevincent.com
- Modern Clutch Alternative: Originals can be made to work by the proud and determined. Give all the purists the slip quitely and install an alluninum basket Ducati clutch available from John Healey at Coventry Spares. With washers, shim the 6 spring buckets for even liftoff and it’ll work flawlessly hot/cold/long storage with the same desirable low lever effort as the original and never needed adjustment or servicing.
- Clutch Rod (Original): Clutch disengage. Early models had single rod all the way through, install the two-rod-ball-in-middle version.
- Modern Throw Out Bearing: It can be very difficult to get the pilot clutch plate to lift off evenly all the way around which leads to drag, especially when warm, and difficult in selecting first gear from any position other than neutral. Norman Walker with the VOC (timetraveler on the forum) sells this kit. #1 points to the replacement for your adjuster (C26), in some rare cases C23's may not have an outward portruding raised lip in the threaded section causing this nut to nest in to far. If your C23 does have this pronounced lip, advise in order to his email address email@example.com (click here to generate an email to him) and he will supply the suitable distance piece with the kit.
#2 illustrates how your pushrod now nests in this piece to ensure square lift off. #3 shows how the bearing is nested in the unit ensure/reduce any grease is not centrifuged off onto your C24. #4 indicates how centralizing is ensured. You’ll not the pushrod is hardened on the end abutting your bearing. Norman advises to back your ET27 out as far as possible, fit up the assembly and then trim (carefully) the end of the pushrod inserting into your new C26.