I Gotta Beeg Problem

I've been fighting a sooty sparkplug in the 3rd cylinder of my '75 Z1B 900. Tried the WG coil relay mod, checked compression, valves, fuel levels with the clear tube method, put in Z1Ent carb kits, dialed it in with the online help of this forum, including wiredgeorge. Still problems.

Mostly at low throttle opening levels and rpms, stutter, runs ratty. Very good at middle and higher, strong acceleration.

Tonight I pulled the carbs, recleaned them (4th time), checked the plugs. When I put the plugs back in, the 3rd, the problem cylinder, wouldn't tighten. I've been very careful, but I think the threads have worn down. I've always hand threaded it in, to ensure I don't strip the threads. Not cross threaded, just worn down. Little metal shavings around the top of the plug opening.

So, what do I do? Will teflon tape work on a temporary basis? Do I have to pull the heads, and, ... what?

I'm bummed.

Epoxy!


No, really, I'm just kidding. Could you move up to an 18mm plug. Is there something resembling a8es??

How about just bore it to 18mm and screw a 14mm-18mm adapter in it...?

you need to helacoil the head to fit your plug

I not familiar with a helacoil. Is that when you drill our the hole and thread in a new threaded opening? I guess that involves pulling the head, since I don't want shavings in the cylinder. Sounds like something a machine shop does, rather than little ole me.

Do what I did...go down to ACE hardware and get a
14mm plug rethread kit that they sell.

Its better that a heli-coil and easy to do. Coat
the rethreading tool with grease and it will hold
onto the chips. What few chips that do fall in
the cylinder won't hurt nothin.

I'm over here in Emmett by the way...

Bob

go to napa, get the thread inssert, it will last longer than a heli coil, if you dont want to pull the head, coat the tap with grease it will catch most of the shavings, use a shop vac and rig up some hose to go inside the spark plug hole to suck it out before installing the plug and running it

Sounds like you have some good ideas to work with so far. My first guess was a helicoil.

Almost forgot check the chock plunger o-rings. Take the enrichening valve out the sooty spark plug cyinder and switch it with another cylinder and see if it soots a different plug.

There has been a lot of talk over the years whether it is necessary to remove the cylinder head or not to repair spark plug hole thread. I personally would remove the head. Get a new head gasket. Re-anneal your four outer bronze crush washers that go over the engine studs and pull the head off. I just don't think you can do a good enough job of keeping shavings out.

I personally won't use Helicoil brand thread repair kits for spark plugs. I use NAPA brand as they are ONE PIECE and won't unwind over time. They install using anaerobic thread locker to hold them and if it ever fails and the insert comes out with the plug, you can just clean the insert and put it back in.

NAPA has two lengths of spark plug insert. Once is 1/2" and is too short and the other is 7/8" and a tad too long. Get the longer and cut it to the proper length.

Cutting the thread is HARD TO DO... see if they have instructions on drilling the hole which makes the job a lot easier.

Good luck... if you have the opportunity to buy Timeserts, these are superior to other inserts but do cost a bit more. There are plenty of inserts on the market and in this application, a solid insert is better than a coiled wire type.

Thanks again, guys. I guess I have yet another opportunity to learn something. Thread inserts, here I come.

Didnt kknow that there was a difference:huh: in inserts. I thought that all there was is helicoil. What do the other ones look like?

the inserts are thin ss with a shoulder to seat the plug and the insert to the head, that way when you install a plug all the thread pressure is on the insert not on the threads in the head