2. Engine - Timing Case
The timing case of a Vincent twin is a relatively busy place, certainly
there are quite a few bits in there, especially if you have to replace
The Timing Case Itself
Cam and Follower Spindles :
|Exhaust Valve Lifter Assembly:
At first I was not going to fit the valve lifter mechanism, partly because I didn't have the bits but mainly because for racing I was concerned it might come adrift and damage the engine. Actually, now I think about it, I am not sure if original Lightning's were fitted with the valve lifters, but I assume not.
Anyway, as my plans for the bike have now changed and I might consider putting the bike on the road, I have decided to fit the valve lifter mechanism. I was lucky enough to pick up the main lifter arms a few years ago and the remaining parts have either been made up or purchased from Maughan's.
It took a lot of fiddling before I was able to get the adjustment of both lifters right, it being very difficult to stop one of the lifters lifting even when it was not being pulled. Eventually I found that one of the lifters was fouling the timing case, which was cured by grinding a fraction away.
At a recent Mallory race meeting, I did ask someone who had raced Vincent engines for many years his view on fitting valve lifters. He seemed most surprised at my doubt over reliability, having told me he had fitted them for years!
|Cams and Followers
Like most racing people, I decided to use MKII profile cams, I don't know if other racing people have developed a better profile over the years but if so I haven't heard about it, therefore it seemed a quite straight forward decision. I had managed to get hold of one original MKII camshaft (the larger one) in very good condition, but with the other had to get a very ropey standard cam re-profiled.
Actually, from a restoration point of view it was quite a luxury for me not to have to worry about this area myself, just contract it out to that well-known Vincent cam exponent - Gary Robinson in the Isle of Wight. With my racing ES2 (see Other Bikes section), I was more used to having to draw out a valve lift graph and then convert that into a wooden blank. I would then use this as the 'master' on a jig I had made for grinding cams, a laborious and time consuming job with sometimes mixed results!
As well as sending the cam for re-profiling, I also sent a set of followers for stelliting. In both cases the quality of the work that came back was first class. Since then I have also stellited a second set of followers myself, as spares. It is a bit of a acquired skill stelliting, where the stellite is applied once the base metal starts to 'sweat' as opposed to looking for fusion as with normal welding.
To help with the process of stoning the followers after stelliting, I came up with the idea of a small jig that holds the follower secure. This could be adjusted so that the follower face can only be stoned to a certain depth, while being held parallel to the spindle hole (see photo).
Final job was to highly polish the followers, standard procedure for most racing engines, with Lightning's no exception.
|Timing Case Gears:
The biggest gear in the timing case is the idler gear. There have been a number of different types over the years, made from bronze, aluminium and steel. The aluminium version for many years was fitted as standard, but is not considered by many as strong enough for racing.
When I bought the Vincent another of the 'goodies' with it was a brand new steel idler gear. It was only recently, when I came to fit it that Steve (Maughan) and myself discovered it was slightly oversize. Only a few thou, but enough to ensure that we could not find a crankshaft gear with enough clearance.
Luckily, Steve and Graham at Maughan's had previously made up a batch of special racing idler gears and had one left. As well as being of correct size and being drilled for lightness, it is also slightly slimmer in width than a standard gear. Although, in theory this might mean slightly more wear it also means less weight and less friction - they look very pretty too!
I did have a set of original camwheels in good condition but could not resist a set of Maughan's racing camwheels, which are drilled for lightness and just look the business! The cams were pressed on to the camwheels with the help of Maughan's special jig, which sets the all-important position of the cams in relation to the wheels. When the first cam came back from G.Robinsons after re-profiling, I noticed he had put a line of weld between the camshaft and camwheel, to prevent any movement. I thought this a good idea so duplicated it on the other cam.
Final job was to press new phosphor bronze bearings inside the camshafts, then ensure they ran freely on the spindles. Job done.
|Idler Wheel Boss:
Similar to the steel idler gear, the alloy idler spindle housing, fitted as standard, should be replaced by a steel bossed version if serious speed work is considered. Again, this was another of the goodies that came with the bike.
This boss holes are drilled slightly oversize, so the boss/spindle can move slightly on its mounting studs in the timing case. This allows the correct gear backlash to be set with the cam wheels before the nuts are tightened, then locked, to stop the boss moving. Rather than using the traditional method of punch locking, once I had set the correct gear mesh I used more modern Nyloc nuts to lock the boss in place, along with Studlock for good measure.
With the idler gear set in position to give correct mesh with the camwheels, it is then necessary to fit a crankshaft gear (ET49) with the correct oversize/undersize to ensure perfect mesh with the idler gear. Again, Maughan's can supply these in all sizes, although it is recommended to take the complete engine to them, to ensure the correct gear is selected. As I had already done this, to have the crankshaft balanced, I sized the gear at the same time.
|Next gear to be looked at was the
breather gear (ET141). This is actually a standard size ET49 gear, but with
a slotted sleeve fitted that works in conjunction with the slotted spindle
to offer effective breathing of the timing case. The bike came with an original
gear but this had a badly chipped tooth as well as a worn alloy sleeve.
Maughan's supplied a very nice ET141 with a phosphor bronze sleeve fitted.
When I was fitting it, I realised it did not have the 'B' mark etched on it, so rang Steve at Maughan's for advice. He told me the method used to ascertain the mark; put a ruler over the flat of the phosphor bronze bearing slot. Then looking at the gear, as it would be when fitted in the timing case, find the tooth that intersects with the flat of the ruler, on the right side. Finally, go one tooth further clockwise and that is the correct tooth. Simple!
|The only gear left replace was the magneto gear, so as you probably guessed, I replaced that too. The fibre gear supplied with the bike was reasonable, but did not look quite good enough quality for serious racing, so a new Maughan gear was fitted. I will also fit a rev counter, so needed to fit the quite elaborate set of parts needed to do so. Maughans makes all these parts and again, the quality is superb. With these parts fitted it is no longer possible to fit the road going automatic advance/retard unit, however, as the bike is fitted with a manual KVFTT magneto this is not a problem.|
Assembling the Gear Train
|That about completes the timing case.
Obviously the timing cover parts, including oil quill have all been replaced.
Currently I have a problem with the original pressure release plunger been
very stiffly jammed in the timing cover, I'm sure I'll figure out how to
get it out though.
As I described in another section, the oil pump was also replaced with a twin pump, so all in all, I guess that I must have replaced or refurbished almost every part in the timing case. Not sure I would like to sum up the cost, but hey, it's better than peeing it up a wall . . .