[GlennF]

Tighten plugs firmly but not too tight.  If you can turn it by hand without a spanner its too loose

With an alloy head there is a very real risk of cross threading or stripping the thread in the head if you get too flamboyant putting the plugs back in.

[Arizoni]

You should have been able to screw the sparkplug into place with your fingers using just the socket wrench until it stopped.

Then, using the bar thru the wrench for leverage you should finish the tightening by using quite a lot of rotational force to compress the gasket.

If you had used a torque wrench with a socket the value you  would be tightening to would be about 20 foot pounds (although 15 would probably do if an anti-seize compound was applied to the threads before installing the spark plug ).

To give you a feeling for what 20 foot pounds of force is, that is a 20  pound load applied to a bar or rod that is one foot from the spark plug.

If the rod or bar was only 6 inches (1/2 foot) long a 40 pound load would need to be applied.

If the spark plug was installed to seat against the gasket but was not tightened down enough the engine would probably run all right but the spark plug would overheat if the engine was run fast.

The spark plug needs to be tightened so it can transfer its heat to the cylinder head.

Not pushing the spark plug wire boot fully down onto the spark plug is one possible reason for misfires after changing the spark plug.
If the wiring connector is not making contact with the metal thread on top of the spark plug the spark will have to jump some distance from the wires connector to the tip of the spark plug.

This works pretty well when the engine is just idling but when the engine must produce power the higher pressures in the cylinder can keep the plug from firing.

[singhg5]

So my question is, how far down is it supposed be tightened? All the way?  

After NGK spark plug is screwed as much as possible with fingers, use a socket and turn 1/2 to 3/4 TURNS.  This will compress the washer on the spark plug to right tightness.

The reason for 'lurch and stall' - may be that spark plug cap is not firmly connected to spark plug (As Arizoni said).  PUSH Down the cap on spark plug or Tap it gently a few times with the back of a screw driver until it stops going any further.

You can also check Clutch play, it may need adjustment to 2 - 3 mm.

Also check Idle setting, 1050 rpm works well.

[Pauly]

also did you check your plug gap before insatlling, saome say they are "pre-gapped" but always check them anyway

P.S. shes running great with the champion plug in

Pauly

[aikischmid]

Awesome - you guys rule! Thanks again!