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Author Topic: Should I be worried (cracks in head)?  (Read 6586 times)

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Offline Noddy78

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Should I be worried (cracks in head)?
« on: April 16, 2015, 09:25:33 PM »


Thoughts?
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Offline scottly

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Re: Should I be worried (cracks in head)?
« Reply #1 on: April 16, 2015, 09:31:25 PM »
Yes, those cracks are a problem. Time to look for a new head or a good welder/machinist. New head would probably be cheaper than repairing....
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Offline Don R

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Re: Should I be worried (cracks in head)?
« Reply #2 on: April 16, 2015, 09:31:34 PM »
 Yes it's time to worry, the crack can loosen the seat and cause it to drop not to mention the obvious compression loss / broken part falling into the engine.
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Offline Stev-o

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Re: Should I be worried (cracks in head)?
« Reply #3 on: April 16, 2015, 09:41:47 PM »
I wouldn't be worried, I'd be lookin for a new head.
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Offline SOHC4 Cafe Racer Fan

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Re: Should I be worried (cracks in head)?
« Reply #4 on: April 16, 2015, 10:03:04 PM »
Time for a new head.
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Offline Noddy78

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Re: Should I be worried (cracks in head)?
« Reply #5 on: April 16, 2015, 10:13:52 PM »
#$%*, that's what I was afraid of. Surely the machinist should have picked those up when he was lapping the valves and installing the new guides? Looks like I've got some yelling to do...
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Offline brandEn

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Re: Should I be worried (cracks in head)?
« Reply #6 on: April 16, 2015, 10:19:38 PM »
Time to find a new machinist.
seriously...
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Offline Retro Rocket

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Re: Should I be worried (cracks in head)?
« Reply #7 on: April 16, 2015, 11:19:46 PM »
Quote from: brandEn on April 16, 2015, 10:19:38 PM
Time to find a new machinist.
seriously...

And a refund, what an arse...
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Offline lrutt

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Re: Should I be worried (cracks in head)?
« Reply #8 on: April 17, 2015, 04:21:11 AM »
never seen cracks that big in a head before. wow.
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Offline evanphi

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Re: Should I be worried (cracks in head)?
« Reply #9 on: April 17, 2015, 05:50:37 AM »
Quote from: Retro Rocket on April 16, 2015, 11:19:46 PM
Quote from: brandEn on April 16, 2015, 10:19:38 PM
Time to find a new machinist.
seriously...

And a refund, what an arse...

If they didn't see it, stop work, and tell you about it... they probably caused it!
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Offline Stev-o

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Re: Should I be worried (cracks in head)?
« Reply #10 on: April 17, 2015, 07:25:15 AM »
Quote from: evanphi on April 17, 2015, 05:50:37 AM
Quote from: Retro Rocket on April 16, 2015, 11:19:46 PM
Quote from: brandEn on April 16, 2015, 10:19:38 PM
Time to find a new machinist.
seriously...

And a refund, what an arse...

If they didn't see it, stop work, and tell you about it... they probably caused it!

That brings up a good question: what would cause cracks such as those?
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Offline flybox1

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Re: Should I be worried (cracks in head)?
« Reply #11 on: April 17, 2015, 07:34:45 AM »
heavy handed with the valve seat cutter maybe? 

your only hope might be that you've got a few good 'before it went to the machinist' shots of this area  :-\
« Last Edit: April 17, 2015, 07:36:31 AM by flybox1 »
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Offline 754

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Re: Should I be worried (cracks in head)?
« Reply #12 on: April 17, 2015, 07:51:02 AM »
I was going to ask if it had compression, as I recall an old dragbike single that had cracks like that but ran fine.  I think though on my Ducati single , it was blowing back thru the intake when it cracked.

I got a 750 72 750 head that has two seats that look like the sealing surface. Of the seat sunk down about 1/8 inch..not sure what happened there.

I am not not thinking of any scenario where working on it could have caused that.
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Offline madmtnmotors

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Re: Should I be worried (cracks in head)?
« Reply #13 on: April 17, 2015, 07:58:45 AM »
Almost looks like the piston struck the spark plug.
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Offline calj737

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Re: Should I be worried (cracks in head)?
« Reply #14 on: April 17, 2015, 08:01:44 AM »
I was going to say it looks to me as though the seats are the source. Widest crack begins on both seats, then travels to plug hole. Also upper seat looks chipped where it approaches the lower- Be interesting to hear from Mike R on his opinion to cause and recommendation.
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Offline iron_worker

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Re: Should I be worried (cracks in head)?
« Reply #15 on: April 17, 2015, 08:19:14 AM »
What bike is this off of that has valve seat inserts?

I would definitely be looking for a new head. You could have it welded but I think with the time that it would take to do it properly in prep, welding, and machining you would $ ahead to just get a new one.

IW
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Offline PeWe

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Re: Should I be worried (cracks in head)?
« Reply #16 on: April 17, 2015, 12:05:52 PM »
I have no experience at all regarding head damages. But I can find others with help of Google.
I found one other case where the reason was said to be overheating. Lean carbs, not closing valves or late ignition?
http://georgiajag.com/Documents/HeadArticleJCNA07/XKHead.htm

I'm happy that my cb750 head  did not crack when I melted a hole in a piston back in the days, rods bluish in the upper end. Also close to crack my head 4 times when I was much younger, a few stitches each time
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Offline LesterPiglet

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Re: Should I be worried (cracks in head)?
« Reply #17 on: April 17, 2015, 12:33:40 PM »
That seat is definately farked and there is another small crack between the seats as well.
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'Then' and 'than' are completely different words and have completely different meanings. Same with 'of' and 'have'. Set and sit. There, their and they're. Draw and drawer. Could care less/couldn't care less. Bought/brought FFS.


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Offline Noddy78

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Re: Should I be worried (cracks in head)?
« Reply #18 on: April 17, 2015, 02:57:54 PM »
Great, thanks for the replies guys. Follow up question, they installed new valve guides in this head, if they remove them again are they useable in another head, or are they a once-only type deal? This is the best 'before' shot I've got - looks to be cracks there already, but I asked them to see if they coud fix the rusting on the valve seat, so that's the same cylinder:



Also, if we're trying to figure out what happened, bear in mind these also came out of the same engine:



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Offline calj737

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Re: Should I be worried (cracks in head)?
« Reply #19 on: April 17, 2015, 05:42:43 PM »
Yeah, I would not jump to the conclusion that the machinist is responsible for the damage of that head. I think we all agree a new head is in your future. Just make sure it fits your cylinders and not your hat size!  ;)
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Offline BPellerine

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Re: Should I be worried (cracks in head)?
« Reply #20 on: April 17, 2015, 05:43:26 PM »
cam towers must have gotten loose at one time,maybe due to stripped threads and the whole thing was floating around rubbing on cover.bill
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Offline Retro Rocket

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Re: Should I be worried (cracks in head)?
« Reply #21 on: April 17, 2015, 06:09:11 PM »
Quote from: calj737 on April 17, 2015, 05:42:43 PM
Yeah, I would not jump to the conclusion that the machinist is responsible for the damage of that head. I think we all agree a new head is in your future. Just make sure it fits your cylinders and not your hat size!  ;)

I think the damage was originally there, the machinist needs his head read for doing the seats on that head.... :o
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Offline PeWe

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Re: Should I be worried (cracks in head)?
« Reply #22 on: April 18, 2015, 03:15:08 AM »
Is the cam ear really welded? This indicate a series of severe events, or is it one only that cracked head and broke cam?
I remember that kind of cam damage and found the thread.
http://forums.sohc4.net/index.php/topic,125377.msg1424921.html#msg1424921
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http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline LesterPiglet

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Re: Should I be worried (cracks in head)?
« Reply #23 on: April 18, 2015, 05:33:31 AM »
Ive also had a cam like this. The owner broke it peening the bolt.  :-\
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'Then' and 'than' are completely different words and have completely different meanings. Same with 'of' and 'have'. Set and sit. There, their and they're. Draw and drawer. Could care less/couldn't care less. Bought/brought FFS.


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Offline Lostboy Steve

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Re: Should I be worried (cracks in head)?
« Reply #24 on: April 18, 2015, 06:39:51 AM »
Wow. That's a good one....


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