Author Topic: 350F head inspection. Is this any good?  (Read 1017 times)

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Offline fmctm1sw

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350F head inspection. Is this any good?
« on: January 19, 2009, 04:51:31 PM »
If you followed my other threads about burning oil, thanks for the replys.  So I decided to see what level of effort was going to be required to replace my stem seals WITH the engine still in the frame.  I picked up a spring compressor at Autozone and decided to practice on the original head that was in my bike.  It was locked from sitting 15 years and I found another engine locally and popped it in figuring I'd rebuild the original later.  I was growing dishearted knowing Honda didn't put stems seals on the exhaust valves and knowing I may have no other option down the road than new guides (and valves.. and finding someone to do it.. etc).  I get one exhaust valve off and I find a stem seal.  Oddly, all 4 exhaust valves have stem seals.  Whatever was done was done a long time ago.  I bought it in 1988 and it sat in my Mother's basement all those years.  The bike was a 1973.  I'm hoping someone put new guides in it and didn't just jam stem seals on it (that would be my luck).  And speaking of my luck, look at the bearing surface.  It looks damaged.  There is nothing obvious on my camshaft but I may have swapped the cam into another engine I have.  And it might be in a bike I sold, not sure.  I planned on replacing the stem seals, cleaning up the valves and trying it out but I'd hate to sieze anything if that bearing surface is shot.  Then again, if I did, I could pop the guides and valves out and put them in another head?
« Last Edit: January 19, 2009, 04:54:56 PM by fmctm1sw »
Quote from: 754
Dude is that a tire ? or an O-ring..??

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This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
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Offline OakBehringer

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Re: 350F head inspection. Is this any good?
« Reply #1 on: January 19, 2009, 05:08:30 PM »
Those seals aren't just "jammed on" - I don't think that would even be possible. If it is, it wouldn't look like that.

Can you re-use the valves? Maybe - depends on a few factors. These are the same questions you'd be asking yourself if you were putting the valves back in their original head.

- The stem needs to be measured for straightness and wear.
- Judging by the corroded sealing surface on the bottom of the head, the valves are probably corroded too. They would most likely need to be re-ground. Oh yea- putting them in a new head? I assume the head and valves will need to be ground to have matching surfaces.
1974 350 Four - SOLD
1966 CL160
1981 XS650
1972 CT70

Finished CB350F

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Offline Bodi

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Re: 350F head inspection. Is this any good?
« Reply #2 on: January 19, 2009, 07:24:05 PM »
I wouldn't plan on using guides twice. Others may have experience with such a trick, but I haven't. After pressing the guide in the hole must be reamed to final bore, presumably because the guide is squeezed a bit smaller by being pressed in the head. Would two heads have exactly the same guide hole size?
After installing new guides the valve seat face on the head has to be recut to ensure concentricity, then the valve is lapped in to seal. Changing seats is not an economical proposition, and you only get a few recuts before the seat is too far recessed in the head.

Offline many408

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Re: 350F head inspection. Is this any good?
« Reply #3 on: January 20, 2009, 11:29:18 AM »
And speaking of my luck, look at the bearing surface.  It looks damaged.  There is nothing obvious on my camshaft but I may have swapped the cam into another engine I have.  And it might be in a bike I sold, not sure.  I planned on replacing the stem seals, cleaning up the valves and trying it out but I'd hate to sieze anything if that bearing surface is shot.  Then again, if I did, I could pop the guides and valves out and put them in another head?

Those don't look too bad; the outboard ones are the ones that go first.  If the cam is smooth I'd put it in and see how it went...you'll probably heal a bit of squealing just before (~30 seconds) it does any galling.    Change the oil and filter frequently.