Need help, cracks in combustion chamber?

[eran_k]

I took of the head yesterday and today after a good cleaning i noticed what looks like cracks in the head near the spark plug hole.
i'm hope i'm mistaken and they are not cracks but some casting marks or something.
they appear the same shape and location on both cylinders. i took off the head of my second bike and although it had lot of carbon deposit it looks like there are the same "cracks" on it as well.
I tried to take pictures i hope they're clear, these are the two cylinders.

 

[chuck hahn]

The two look like the same marks in the same spots. Right now I am thinking casting marks. They didn't have to be perfect and this seems like the case to me anyway.

 

[posplayr]

I had a head on an 1100e 16v and it did not seem to hurt anything

 

[eran_k]

I had a head on an 1100e 16v and it did not seem to hurt anything

Sorry, not sure i understand. do you mean you had the same thing on a 16V head?

 

[posplayr]

Sorry, not sure i understand. do you mean you had the same thing on a 16V head?

Yes same cracks on at least one cyclinder ; put it back together with no issues.

 

[rapidray]

I build heads & those cracks make the heads junk. If I get one that has a lot of money in it, porting wise, we will weld them up & fix them. Cylinder heads crack between the plug hole & exhaust seats due to heat, detonation, or both. You can keep running it if you want but check to see it isn't leaking. To ME, cracks like that make need for a replacement. Ray.

 

[rapidray]

You can check to see if the head leaks through the cracks by doing a leakdown test & spraying soapy water around the spark plug hole when you are leaking it. Of course, this needs to be done with the head on the motor & torqued like it is ready to run. Ray.

 

[blowerbike]

this is common on turbo 16v. heads...
i still have a record setting star head from 87 that looks baddd around the plug holes but still performs.
run it till it won't run no more!

 

[Guest]

Seen cracks you can fit a dime into,
I suppose once you have the spark plugs out you can see if the crack has propagated up the threads. The spark plug should seal it though. You could set the head upside down and fill the combustion chambers full of solvent or something to see if it seeps out. The valves might leak more than those cracks.
I'd ignore them.
As long as they don't go I to the water jacket it should be fine.

 

[Guest]

This is a common problem on the older twin 8 valve engines. I think after 83-84 they made a change to the head that fixed that problem.
Some have even seen it crack bad enough to leak out the plug hole and puff like a steam engine. I'd use a different head if possible, or run it until it gets bad.

 

[blowerbike]

water jacket??
just checking

 

[tkent02]

Just a guess, you think these cracks form from running a cold engine hard and heating it up too fast?

 

[GregT]

This is a common problem on the older twin 8 valve engines. I think after 83-84 they made a change to the head that fixed that problem.
Some have even seen it crack bad enough to leak out the plug hole and puff like a steam engine. I'd use a different head if possible, or run it until it gets bad.

Correct - and it's what you were warned against too on your one...

I'd doubt if there's a lot of heads in the middle east and your chances of getting a good one off ebay are probably pretty slim. From personal experience they will go for a long while with cracks like that. it is possible to machine out the inserts and weld/remachine etc but it's a difficult and costly job....never know, someone here may have a good head.

 

[eran_k]

Well i went to a specialist machine shop today that only do heads, the guy inspected the head and said it's good. so with that and the opinions here i'm going to use it for as long as it'l work.
Thanks
Eran

 

[eran_k]

Two better shots,each one is a different cylinder

 

[Steve]

As long as they don't go I to the water jacket it should be fine.

It would have to be a pretty BAD crack to get into the water jacket on a GS. :-\\\

.

 

[sharpy]

Well i went to a specialist machine shop today that only do heads, the guy inspected the head and said it's good. so with that and the opinions here i'm going to use it for as long as it'l work.
Thanks
Eran

Car or bike "specialists"?

 

[Nessism]

Big Jay from Ape commented about such cracks in a previous thread (that I can't find), but I seem to remember him saying they are common. Don't think they are a concern unless they open up - matter of degree. If in doubt you might want to shoot him some photos for his opinion.

 

[eran_k]

Some more information;
Today i took the head to a more "motorcycle" oriented machine shop that was recommended by many guys in our local bike forum.
he will take it apart,check all measurements and will give me a verdict.
hopefully it will be in good shape and i can use it.
if it's bad my other option will probably be to use a GS500 top end and see how to work around the exhaust port issue.