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xs650 > > High Performance Modifications > > Top End Work > > A tale of two heads


A tale of two heads
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scotts
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Joined: Apr 03, 2007
Posts: 689
Location: Rock Hill, SC

PostPosted: October 28, 2009, 9:39 am    Post subject: A tale of two heads

I have a running '78 engine with cracked fins on the head.
I have a non-running '75 engine that is frozen. The fins are in great shape.
I'd like to swap the heads when I do a general freshen up on the '78.
My main concern is what happens to the spring tension when valves are stuck in the same position for so long?

I assume that at the very least I'll need to lap the valves and bead blast the head.
Can I swap out the best parts of each head (cam, bearings, springs, rockers, etc.) over to the '75 head and make one good head?
I have not pulled the head off either bike yet, so no visual inspection at this point.
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jayel
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Joined: Apr 16, 2006
Posts: 3417
Location: SE Iowa 1974 TX650A

PostPosted: October 28, 2009, 10:58 am    Post subject: Re: A tale of two heads

the complete heads are the same part numbers as far as I can see, just go thru a parts site and compare numbers
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scotts
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Joined: Apr 03, 2007
Posts: 689
Location: Rock Hill, SC

PostPosted: October 28, 2009, 11:26 am    Post subject: Re: A tale of two heads

I know that the heads will physically swap. I was asking more about springs and valves in the '75 that have been held in the same position for years.
Could I use springs, rockers, valves, etc. out of the '78 head and put them in the '75? Assuming they check out and are in good shape....
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Srinath
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Joined: Sep 10, 2009
Posts: 343
Location: Charlotte NC

PostPosted: October 28, 2009, 11:51 am    Post subject: Re: A tale of two heads

scotts wrote:
I know that the heads will physically swap. I was asking more about springs and valves in the '75 that have been held in the same position for years.
Could I use springs, rockers, valves, etc. out of the '78 head and put them in the '75? Assuming they check out and are in good shape....

When the head is out get a 3 angle valve job and re do the seats etc. That should get it all nice and new and sealing up. The springs and seats should be OK as long as its had no exposure to the elements. The seals should be replaced but they cost very little.
I did that to a GR head that was rusted. Seemed good when done but I am yet to get it on a motor. Springs etc seemed OK.
Cool.
Srinath.
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gordo
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Joined: Oct 09, 2008
Posts: 559
Location: CT.U.S.A.

PostPosted: October 28, 2009, 3:39 pm    Post subject: Re: A tale of two heads

scotts, most machine shop's have the tool used to check spring pressure's. Spring's are usually checked in two spot's, one being at the 'set' height, the other at 'open' height. There is a spec for both height's, can be found in a clymer's or the knuckle buster's site. Or, you could just replace the whole set because being pressed open for so long doe's make them weaker. Your other head's have cracked fin's, so if they have been in use, they should be ok.
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oldkarkid
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Joined: Jan 25, 2009
Posts: 47
Location: Nebraska

PostPosted: December 17, 2009, 12:34 am    Post subject: Re: A tale of two heads

Agreed with Gordo, if you are in doubt, swap your springs too.
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