Cracks in cylinder head

[JHN]

I am working on an engine from GSX400E (82) and just discovered some small cracks around the spark plug hole toward the exhaust valves. I have also checked a spare head I have, and it has the same problem. Is this something to worry about? The attached picture is showing the worst case.

[GregT]

They're noted for it.

I've seen them puffing smoke from around the spark plug but I've never heard of a valve seat falling out. The spark plug threads eventually get eroded away.

The very last model 400 heads are supposed to be better.....We got a lot of the early ones here in New Zealand but didn't see many of the last version.

[JHN]

Thanks for the quick reply. I will go for the cylinder head with least cracks in it and see how it goes.

Are you thinking about the GK53 with black engine?

[Guest]

Couldn't you drill and weld the crack?

Then drill and use a heli-coil for the spark plug?

I'm just curious.

What else is better in the later models?

[Guest]

you could do with removing the exhaust valves & looking to see if the cracks come through into the ports.

[JHN]

I checked the exhaust port and could not find any cracks. I tried to measure the dept of the crack with a very thin tread of steel in it seems to be around 1-2 mm. I will try go get a quote for welding it.

[7981GS]

Can't you find a used non-cracked head for less than the cost to weld/shape that one?

Eric

[GregT]

They can't be safely welded without removing the valve seat inserts - then remachining and reinserting....Welding without removal will inevitably cause the seats to loosen.
They haven't got to the stage of rarity yet where this is cost effective.
Just look for a better head.

[tkent02]

Just look for a better head.

Might as well throw it together and ride while you look for the new head. I bet it lasts quite a while.