Author Topic: Is this head ruined?  (Read 1020 times)

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Offline Untold

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Is this head ruined?
« on: July 17, 2013, 07:15:14 PM »
CB125.  A valve had broken at the stem and punched through the piston. The spark plug was also broken into bits.  There are gouges in the metal, but if the spark plug threads are good, and I lap the valves and they seat ok, are the other gouges a concern?

http://imgur.com/vuCqj8s
1976 CB550K

Offline Greggo

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Re: Is this head ruined?
« Reply #1 on: July 17, 2013, 07:37:22 PM »
It would take some work to save it.  The gouges in the edges can create hot spots, so they have to be smoothed out.  But, how much material will you have to remove to smooth it all out, and then how much will that affect your compression ratio...How much is another head?

Offline kghost

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Re: Is this head ruined?
« Reply #2 on: July 17, 2013, 08:40:07 PM »
Blend it, rethread the spark plug and do the valve seats.

It's a 125. You'll never notice any difference
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Offline trueblue

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Re: Is this head ruined?
« Reply #3 on: July 18, 2013, 02:40:56 AM »
Blend it, rethread the spark plug and do the valve seats.

It's a 125. You'll never notice any difference
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Offline Untold

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Re: Is this head ruined?
« Reply #4 on: July 18, 2013, 06:09:35 AM »
Thanks, I figured it's relatively easy to pull the engine and rebuild, so might as well give it a shot with this head rather than jumping through hoops trying to source another one.  The 125 is just a side toy, so it doesn't need to be perfect, just needs to run.
1976 CB550K