Stuck cylinder head plug

I've got a cylinder head plug that won't budge. This is on a 1979 KZ 750 B twin. It's one of the four plugs that go over the cylinder head bolts.

The other three plugs popped out without much fuss. They're threaded to receive the cylinder head bolts and I was able to pop them out by just running a bolt through and with a little encouragement they popped out.

The fourth one won't budge. I actually broke the cylinder head bolt off in the hole.:S

I guess the next step is to get a drill and try to get the broken bolt out. (Any tips on this would be appreciated.)

Once I get the broken bolt out, what do I do about the stuck cylinder head plug?

picture? :S

Here you go.


That circle in the center of the plug is supposed to be a threaded hole. Instead that's half of one of my cylinder head bolts.

can you push down on one corner and pry it out?

No, it won't move. I tried a little penetrating oil to see if it would loosen it up, but no dice.

Before I sheared off the bolt I had tried gripping and prying the bolt with some pliers. Still no luck.

There's a rubber o ring down in there on the plug. I guess it's swollen or something.

pm steel,he probably knows how to get it out

Topper wrote:

I've got a cylinder head plug that won't budge. This is on a 1979 KZ 750 B twin. It's one of the four plugs that go over the cylinder head bolts.

The other three plugs popped out without much fuss. They're threaded to receive the cylinder head bolts and I was able to pop them out by just running a bolt through and with a little encouragement they popped out.

The fourth one won't budge. I actually broke the cylinder head bolt off in the hole.:S

I guess the next step is to get a drill and try to get the broken bolt out. (Any tips on this would be appreciated.)

Once I get the broken bolt out, what do I do about the stuck cylinder head plug?

It took me a while to figure out your situation, but after studying the parts diagram, I think I've figured it out. The head is held down with studs, not bolts. The nut on the stud under the stuck plug is still there. The plug is threaded for a bolt used only to remove the plug. Am I correct so far? If so, here's what you do. Drill into the broken bolt and back it out with an Easy out. If that wont get it out, carefully drill out the bolt you snapped off. If it was a 6mm bolt, drill 1/4" You'll need to drill down very close to the center of the bolt. When that bolt is gone tap the hole for a 5/16" bolt to try to jack out the plug again. But this time use some heat. You should be able the warm up the area around the plug to about 350 degrees without affecting the aluminum head. Go gently with a propane torch. When it's hot apply some penetrating oil to cool it and heat it up again. The repeated heating cooling cycles will cause a little movement in the stuck parts. When it's hot, turn down that jacking screw and it should come out. If it doesn't, I have further instructions involving explosives. :woohoo:

I took another look at the picture. Get that camshaft out first. In fact take them both out and any rubber parts in the neighborhood.

You're spot on with your assesment of the pic and parts diagram.

Reading your suggestion I was going to ask about rubber parts. There's also loads of motor oil all around there. Will a propane torch be hot enough to catch that on fire?

Topper wrote:

You're spot on with your assesment of the pic and parts diagram.

Reading your suggestion I was going to ask about rubber parts. There's also loads of motor oil all around there. Will a propane torch be hot enough to catch that on fire?

The torch flame is certainly hot enough to start the oil burning but I think it will only burn while the torch flame is on the part. Dry up all the oil you can before proceeding. It will smoke a bit anyway. Of course your carburetors are already off, right? If you're trying to remove the head everything that's attached to it has to be removed anyway.

I'm wondering what the purpose of the plugs is. If there is a threaded hole all the way through oil can just run through them anyway. ????

Do whatever you have to do to get that plug out, then e-mail me your address and I'll send you another one.

TomW wrote:

I'm wondering what the purpose of the plugs is. If there is a threaded hole all the way through oil can just run through them anyway. ????

Yeah I'm not really sure what they're supposed to do. The gasket sort of lays over the holes. I wouldn't think that would do much good, but there wasn't any oil down inside the other three so I guess it works.