The ignition timing mark is on the flywheel. To set the timing, the first job is to remove the flywheel cover. There is a special tool for setting the timing according to the reference mark, but they are no longer available. Don't despair, you can make one.
You will need:
A piece of corrugated cardboard or other stiff card
A piece of plywood or hardboard
A wooden block, about one inch cubed
Some glue
A pencil
Cut the card into a crescent shape - hold it behind the rim of the flywheel and draw the curve, then cut that piece away. You want to make a piece of card that is roughly banana-shaped. The top end of the banana needs to cover the hole of the casing bolt above the engine sprocket, and the bottom end of the banana to cover the hole for the bolt down near the neutral switch. Cardboard is cheap, so keep trying until you can make a shape that fits.
Poke holes in the cardboard with the point of the pencil, where the bolt holes are. Push two of the casing bolts through the cardboard and tighten them. Check the shape and fit of the 'banana' - it needs to lie flat against the joint face of the crankcase, and clear the flywheel and the engine sprocket.
When you have a shape that fits, use it as a template to cut the plywood. Drill the bolt holes, and then bolt it up to the side of the engine.
Remove the spark plug and put the pencil down the hole. Gently turn the flywheel (clockwise as you see it from the flywheel side of the engine) until the piston is at top dead centre. Note where the line marked PMS on the flywheel rim lies in relation to your wooden banana. Glue the small wooden block onto the banana as close to the edge of the flywheel as you can, so that the PMS mark lies lidway along one side of the block.
Go and have a cup of tea, until the glue is dry.
Take the pencil and mark a series of thin lines across it, down its length. Small scratches with a penknife will do. Put the pencil down the spark plug hole again, and very gently move the flywheel backwards and forwards. Watch the marks on the pencil against the edge of the spark plug hole and look for the highest point. When you are sure that the piston is at the top of its stroke, mark the wooden block on the banana with a pen, opposite the PMS mark on the flywheel. You have now made a timing tool.
To set the timing, open the points cover and turn the engine over until the points are at their widest setting. Measure this with a feeler gauge. It should be 0.42-0.48mm. Move the points backing plate to adjust it.
To set the opening point, turn the engine over (turn the flywheel clockwise as you look at it, or reach over the bike from the ignition points side and turn it anticlockwise). Bring the line marked AF 10 on the flywheel up to meet the timing mark on your wodden banana tool. This should be where the points are just opening. Slip a scrap of cigarette paper between the points, and it should be released just as the AF 10 mark passes the timing mark. For greater accuracy use a resistance meter, but do remember to pull the points wire off the coil first, or you will only see a short circuit (due to the neutral and oil pressure switches being closed).
Check the points gap fully opened again, it should still be between 0.32 and 0.48mm. If not, you will either need new points, or to fiddle and file them a bit.
If the autoadvance is worn, it is a good idea to check the timing at full advance. There is no mark on the flywheel for this, so you will need to make one. Use a tape measure to measure around the rim of the flywheel from the PMS mark. The standard 270mm diameter flywheel has a circumpherence of 848mm. The AF 10 mark (ten degrees before TDC) should come at 23.5 mm away from the PMS mark. Full advance is 44 degres, so measure in the same direction as the AF 10 mark a distance of 103.7mm away from the PMS mark and draw a line on the rim.
You will now need to lock the autoadvance at full advance. The ideal tool for this is two of the little alloy nuts that go onto the tops of spark plugs. Pull the bobweights out and jam one of these little nuts under each one. Once you are sure that the unit is locked at full advance, use you cigarette paper or resistance meter to measure the points - they should open just as the new mark goes past your timing mark on the wodden banana tool.
If the autoadvance is worn, it is better to set the timing at full advance. The engine seems to tolerate some inaccuracy at low revs, whereas it can run rough or poorly if the points are not accurate at normal speeds.
And then put it all back together and go for a ride. If the bike does not run smoothly, check your work. If it is still not smooth, try setting the points opening to one or two mm either side of the timing mark and see what works best.
>
Home
Search
Login
Register