A tachometer that shows the wrong reading and get stuck sometimes could be caused by faulty wiring between the transmission and tachometer. It could be caused by a defective instrument cluster.
most likely a vacuum leak
Fuel starvation. Blocked air/fuel filters. Fuel pump delivery rate wrong or carburetor needle valve stuck.
Could be the tach is set for 6 cylinders?
ignition module It's possible that the CDI module went bad. If the car has a tachometer built in to the dash you can use that to make a simple check. Crank the engine while watching the tach. Does the needle on the tach bounce slightly when cranking or does it stay still? If the tach needle doesn't move the CDI module is dead. If the tach needle does move the problem is somewhere else.
Inserts a needle at the wrong angle or uses a large-bore needle
there stuck in china what do you think is wrong with them
It depends on what is wrong with it.The tachometer takes input from the revolutions of the engine, so can you identify if the connection in the engine is okay, or if the connection to the actual guage(tachometer) on the dash is okay.A test would be to get a working instrument panel,replace yours and see if the rev-counter(tachometer) works. If it does then it might be cheaper to replace the whole instrument panel. If it does not then the problem might be in the engine, you might want an auto-electrician to trace the cables etc.
It means you stuck it in the wrong hole!
the person that change the plugs probably knocked the wire that goes to the tachometer off of the distributer. and they either got the plug gaps wrong,messed up the wires to the plugs, or put them back on in the wrong order.
My guess is a stuck ring.
There is something wrong with the tach. Take it to the shop. <--- wow, that is insightful!!