Spark Plug Thread question

When installing plugs on my 75 z three of the four plug holes are very smooth. #2 plug hole is very tight. It doesn't appear to be stripped but the plug goes in with resitance and seems to get harder to tighten towards the head. Any old tricks to fix this problem with the head on the bike. I just installed a new header and smooth bores so the plugs been in and out a few times.
thanks
gregz

Probably ought to chase the threads with a die before you gald them... just clean out the cylinder good afterwards, and oil the threads of your plugs anytime you install them.

Ok. What size tap would I need for a spark plug hole ?

Post edited by: GregZ, at: 2007/09/13 21:49

use anti seize lubricant, as oil has a tendancey to carbon up and cause your plugs to sieze up in the head.

unless you take them out every 100 miles like i do.

GregZ wrote:

Ok. What size tap would I need for a spark plug hole ?<br><br>Post edited by: GregZ, at: 2007/09/13 21:49

Had same problem a long time ago and used an old plug to make a tap. Used a hacksaw blade and cut four slots in the threads and at right angles to the thread. You could probably do this pretty fast if you have a Dremel type tool and a cutting wheel.

Screw in about a turn at a time and remove and check for any metal shavings. repeat etc.

The hacksaw trick can work in a pinch, but I trust a regular tap more as the have more room to get rid of your shavings, which is really important on aluminum.



Any auto supply can set you up with the right tap... just bring in your spark plug for a measurement. They are much cheaper than heads:P

standard 14 mm plug tap/thread chaser