It has more than once occurred to me that since all proper engines contain the same basic components – flywheels, con rod, piston and valve gear – they ought to be more similar than they actually are. In fact, some are lovely and some not so, but I am certain that optimising the timing of any engine will see it at its best.
One of the most useful tools in the workshop is a timing disc. It is the principal method by which we can optimise an engine’s performance. Time and money spent on new engine internals during a rebuild might bring little benefit if the valve and ignition timing are not correct to the manufacturer’s specifications. The most accurate way to confirm this is in degrees of the flywheel.
Setting the timing disc
It is said ‘that a job well started is a job half done’. Good preparation here will be well rewarded later. Take the trouble to devise a robust mounting for the timing disc and attach it to an engine main shaft, the drive side is usually the more convenient. The mounting should allow the disc to be rotated into position and then firmly locked. Make a good pointer with a small range of adjustment. A piece of wire really is not adequate. See picture one.
I have found that there is real benefit in marking on the disc the timing events specific to the engine being worked on, it saves referring to a separate sheet and makes it impossible to time the ignition on the wrong side of TDC (Top Dead Centre) firing stroke.
Accurate setting of the timing disc to TDC is crucial and best achieved using the ‘positive stop’ method. An arrangement to stop the piston at about 40 degrees before TDC has to be made. With the cylinder head on, this can be an old spark plug body, threaded, with a piece of stud and a lock nut. With the cylinder head off, the cylinder studs can be utilised. See picture two.
This story is from the January 2021 edition of The Classic MotorCycle.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber ? Sign In
This story is from the January 2021 edition of The Classic MotorCycle.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber? Sign In
Runs should be fun
The club run is an integral part of the old motorcycle scene. During 2020, a variation on the usual theme emerged, enabling people to ride in the company of like-minded souls.
Hybrid chicken
BSA Bantams come in many forms, and the ability to interchange parts between different models permits an almost endless number of variants.
Green WITH ENVY
Life aboard a 1950s 350cc British single is perhaps as good and as uncomplicated as it can get.
Worth the wait
Captivated by sight of one as a small boy, finally our man has the chance to try an NSU Max.And a ‘Spezial’ one at that…
The Motorcycle: DESIGN, ART AND DESIRE
The concluding part of a two-part feature, in which the history of motorcycle evolution is examined and a new book’s author interviewed.
Cream rises
There were several ‘star performers’ at Bonhams’ winter sale, as the choice machines achieved huge sums.
The Giant of Provence
With so few events to report from, it’s time to look back over a spectacular French event and look forward to its hopeful resumption.
Store cupboard special
A big box of presents? Must be Christmas! More deliveries keep the project on track.
By 1929, CJP Dodson was a bona fide top level road racer, pretty much unbeatable on the sand, too.
The diminutive Charlie Dodson was the last man to win a TT, the 1928 Senior, on a ‘flat-tank’ machine, then the next year became the first (and only) winner of a TT on a saddle tank Sunbeam, as well as recording the last ever success in the Island for the Marston maker.
Cassandra the Canadian Commando
After landing a new job and with time on his hands, a young man in Vancouver decided to restore a British motorcycle considerably older than him.
