Tappet ticking noise?

[tinram]

Skorpion: If there is a noise coming from the top end that sounds like a tappet, even though the tappet clearances have been adjusted correctly, then the de-compressor mechanism is the probable reason.
It works using a shaft running inside the drive end of the camshaft and is rotated via bob-weights that are located on the drive sprocket. On the inside end of the shaft there is a flat onto which sits a stepped pin with retaining spring. The end of this pin sits proud of the camshaft when the engine is stationary or cranking such that one of the exhaust followers is lifted slightly to reduce compression. As the engine fires up the bob-weights fly out causing the shaft to rotate and the spring to push the pin down out of the way. However, if the spring relaxes over time (as mine did), the pin is then floating and gets smacked back down every time the camshaft rotates. The solution is to buy a new spring or (stretch it slightly if you want to save money).

To lift off the cam cover, the engine does not need to be removed from the frame. Try this…
Remove the seat, side panels and tank.
Then remove the exhaust, radiator and front down tube.
Slacken off the carburettor clips and breather hoses.
Take out the rear wheel spindle and lift off the chain from the rear sprocket.
There are two engine bolts on the top of the cam cover – remove one and leave the other with the nut removed.
Slacken the lower engine-mounting bolt slightly but do not remove.
Place a support under the engine – such as an axle stand or blocks of wood.
Undo the swinging arm spindle bolt and push it out to one side without removing it completely, but enough to free off the engine.
Hold the engine while removing the last top bolt and the engine should be free to swing down by a few inches – enough to remove the cam cover screws.

To gain access to the de-compressor mechanism, remove the two bolts holding the cam sprockets onto the camshaft and lift out.
WARNING: when replacing the camshaft, make sure the de-compressor shaft is in the correct position as it can be fitted 180 deg out, and that the drive pins sit in the slots on the bob-weights. To check, swing the bob-weights out and the pin should retract.

TIP: The thread pitch on the tappet adjusting screw is 0.8mm. So to set say 0.1mm clearance, slacken the locknut, turn the adjusting screw down till it touches, then back off just over 1/8 turn or 45deg before tightening the locknut making sure the screw does not turn further.
Hope this helps somebody.

Cheers tinram

P.S. My 1995 Skorpion Sport is for sale - in North Gloucestershire, UK. Will send details on request