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.
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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 8,500+ magazines and newspapers.
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