Replacing welch/core plug in cylinder head
 

Hi all,

My 1993 XT600Z Tenere has developed an oil leak from the welch plug (aka core plug) that is fitted in the cylinder head to fill the hole where a decompresser shaft would have come out on earlier models.

I have bought a Yamaha replacement part and am wondering on the best way to remove the one that has been there for 20 years. Can I just hammer a screwdriver through it and lever it out? I would rather not take the cam cover off to hammer it out from behind, but I suppose that might be the last resort.

Anyone have experience of doing this?

Thanks

Mark

If it's of rubber then i would try with a simple corkscrew. If it's made of steel then i would weld a 6mm bold to it and pull it out with a slide hammer. If it is made alu the i would drill a small hole cut a thread to it and install bolt and use the slide hammer to pull it.

If that doesnt work then have to take the valvecover off.

Thanks for your reply Christian.

The plug is plastic coated steel. As I don't have a welder or a slide hammer, I am considering passing a very big self tapping screw (with a big washer under its head) through a suitably sized socket in the hope that tightening the screw will draw it out. I have seen a picture of a core plug removal tool that works in this way.

I have also read on a car sites that people just hammer a metalwork chisel through them and lever them out.

Mark

Have you tried just cleaning the surface with rubbing alcohol and then gooping it up with silicon? It isn't a REAL fix but then neither is just replacing the part on a 20 year old engine...

This might help:
Fitting a new oil plug
It's on a TTR250 but probably similar.

I've done the job twice on 250s. Once it came out with some easy levering with a screwdriver.
The other one needed a hole drilled in the plug to insert a screwdriver blade or similar, and lever out.

But,
...sounds the neatest method. Should work unless the plug is real tight. If it doesn't, you'll then have a hole in the plug to help lever it out.

Hi McCrankpin,

I had seen the link you posted (I also have a TTR250) It's interesting but doesn't say how to remove the old one.

I'm probably making a mountain out of a mole hill, but can you expand on what you did exactly when you used 'some easy levering with a screwdriver'?

Thanks

Mark

Hi Mark,

I did this on two TTRs.

One of them was quite easy. The plug is hollow steel covered with thin plastic.
As in the photo, the top of the plug protrudes a little from the head casting. Using a screwdriver with a thin blade in good condition (no rounding of edges) I found the blade got a good grip on the plastic, and could be pushed in a tiny bit between plug and the inside of the hole.
Some gentle levering outwards, with the blade digging into the plastic, got it moving a little, then straightaway repeat in a different position, then again further around the part of the plug that's accessible. Then it came out fairly easily.
Look at the picture of the removed plug, you'll see the gouge marks on the edge.
Take care not to damage the inside of the hole.

On a different bike that process wouldn't work. So I drilled the face of the plug (a bit of grease on the drill bit to try to stop swarf entering. But if it does it's easy to clean out I think).
Then a decent pin-punch or similar in the hole and the plug levered out, after a bit of effort and bending of the plug. Use a good punch, if the tip breaks off while levering it might make things difficult.

For belt-and-braces I smeared a bit of gasket goo on the new plug.
Hope that helps.

Hi again McCrankpin,

Thanks for that excellent description. Not sure if the plug on my Tenere protrudes enough to stab a screwdriver into the side as you described, but I will give it a go before resorting to more involved methods.


:offtopic:By the way, really enjoyed reading on your web site your memories of your father's motorcycling times in the 1950's.

Mark