TOPIC:

I had to redo the threads on one of the spark plug holes some time back and have read on here that some people replace them all. I will tearing the engine down over the winter and was wondering would it be worth the trouble to do the other three while the head is off?

"if it ain't broke don't fix it"

it is so easy to put a heilicoil in the spark plug threads with the head still on the bike until it's probably not worth the time nor money to do it now.

First, I personally would not install anything in the plug holes that required cutting while the head was on the bike... just too much metal. I know that you can do several things to keep the mess down but it scares me and would just as soon remove the head.

Second, helicoils are the worst choice as they are coiled wire that forms thread and these things have a tendency to back out when you remove the plugs. I suggest Timeserts OR NAPA sells a one piece insert. Get the 3/4" and cut it down some so it doesn't protrude into the combustion chamber. The NAPA insert is retained by using Loctite permanent red anaerobic stuff.

Last, I wouldn't fix thread using inserts that doesn't need fixing. You can clean the thread using a 14mm chase... run it through and it will clean up thread...

Post edited by: wiredgeorge, at: 2005/11/22 09:33

usually what i do is apply wheel bearing grease to the tool when cutting new threads. I'll make a couple of turns and back it out cleans off the old grease with the embedded metal shavings and apply new grease. I repeat this process until i have finished cutting the new threads. it works for me and is certainly faster than removing the head. However i do agree that removing the head is the most recommended way.

george is right, the insert is the best way to go, a heil coil will gauld to the spark plug at some time, they will back out with the plug, along with the insert or even just installing the plugs you should get the copper anti seize and apply a small amount to the plug threads to prevent problems

The last time I did it I used an insert. The depth was perfect and I had the head off, fixed and ready to put back on in approx 3 hours. I will be taking the head off over the winter and thought I would do some preventitive maintenance. I had read here before that some people redo their plug holes for that reason. The insert that I used required high temp rtv silicone and a curing time of 24 hrs under normal conditions.

If you are drilling the plug hole first set the motor up so the intake is closed and the exhaust is open. That way you can blow the pieces out with air when your done.