Topic: Engine builders: I need your eyeballs on this 750 combustion chamber

[Brantley]

Chopstick is pointing to a raised edge that I believe is the outside of the valve seat. I can just snag my fingernail over it. To the left and below is a small dent I found beneath all the carbon. No damage to the piston, valve or seat. Do these issues need addressing (other than the obvious cleanup)? Thoughts on effect on performance/ reliability?

Edit: I suppose I should be more specific in my questions... One valve stem is dented and needs replacement- I have used spares. Planning on having all refaced, installing APE guides, and having the seats recut. Don't really want the expense of replacing the seat or wasting money on all this machine work if that valve near the dent will be in danger of burning. Can I grind that little lip down to match the chamber? This is a K4 head- I have a K3 I could use but is in worse condition in other areas (rust on a few valve seats, ports need more attention, etc.)- and want it to "match" the K4 jugs I've already over bored.

[lucky]

It is not clean enough to tell what is going on.

[Brantley]

It is not clean enough to tell what is going on.

Chopstick is pointing to a raised edge that I believe is the outside of the valve seat. I can just snag my fingernail over it. To the left and below is a small dent

[Old Scrambler]

Apply some brake cleaner and give us a better pic.........I think all will be good after you re-surface the seat and valve.  I had a similar value problem on my K3 and had to replace that one valve because it was worn to the point was recessed into the seat and I had no adjustment left on the rocker.  All seems good after a few thousand miles.

[cgswss]

One of the problems with running no lead gas in an engine make for premium leaded gas it that the valves beat the crap out of the "soft" valve seats.  I can't help but wonder if this isn't the result of something like that.  At any rate, My old eys thick they see metal movement inside that chamber.  You get that engine tuned right (leaned out enough to give best performance) and get the head temps up high enough and that ridge might cause detonation.

At any rate, If I were working on that head, I'd be doing some cutting on those chambers (so all are the same).  I'd be putting in hardened valve seats too.  But then again, I'm like Mike Holmes (the builder guy on TV) "Tear it all down and make it right!"

On the other hand, if you can clean up the valve seat and get it to seal, I'm sure it will run just fine for as many miles as you choose to put on it.  Lets face it, how many times do you ask 100% power out of your engine on the street?  If your still driving, not often.

[Brantley]

One of the problems with running no lead gas in an engine make for premium leaded gas it that the valves beat the crap out of the "soft" valve seats.

Didn't the old tank stickers read something like, "Use unleaded gas, wear a helmet, preserve nature"? Confused.

At any rate, My old eys thick they see metal movement inside that chamber.  You get that engine tuned right (leaned out enough to give best performance) and get the head temps up high enough and that ridge might cause detonation.

Are you talkin foreign metal or shifting of what's supposed to be there? Every other time I've seen foreign matter in a cylinder/ combustion chamber there are signs of entry or exit on the valves or seats. As I said I see none. I am worried about heat as I am gonna run an 836 kit and the only other one I've had was super hot.

At any rate, If I were working on that head, I'd be doing some cutting on those chambers (so all are the same).  I'd be putting in hardened valve seats too.  But then again, I'm like Mike Holmes (the builder guy on TV) "Tear it all down and make it right!"

On the other hand, if you can clean up the valve seat and get it to seal, I'm sure it will run just fine for as many miles as you choose to put on it.  Lets face it, how many times do you ask 100% power out of your engine on the street?  If your still driving, not often.

I am planning on light porting and cleaning up the chambers. Don't get me wrong- it's tore down for a reason- to get it right. I'm mainly wondering if this is salvageable without replacing the seat as the valves actually seal quite well- several days of sitting upside down with the chambers FILLED with WD40 yielded very little leakage. This is planned to be my new daily. I have no illusions about my riding ability (I aint no roadracer), but I do like to use the power available...

[Don R]

Hard to see but it appears smoothing that area might unshroud the valve. that's not such a bad thing just match all 4. if it's indented past the seat then maybe another head might be better.

[bryanj]

These are designed to run unleaded and i wouldnt trust a Honda head with a replaced seat--far better to get another head in better condition, probably cheaper too.

[Brantley]

Hard to see but it appears smoothing that area might unshroud the valve.

I'll try to get a better photo up tomorrow after another cleaning (you should have seen it before). Thought that the carbon contrast made what I'm trying to point out easier to see. Then again, I have a three dimensional reference... The slight crescent moon shape is the edge of the steel (?) valve seat protruding slightly above the aluminum. Thanks for the input so far, fellas.

[dave500]

it looks like maybe water has been sitting and corroded the alloy away exposing the seat?is the seat fully seated,can you see where it should bottom out in its opening?

[MRieck]

Bead blast that chamber and the ports....you have to R&R guides. That casting anomaly won't effect anything but you can grind it a small amount to get rid of any sharp edges. I have a head sitting on my bench that has the same type of casting.....obviously caused by the die used by one of Honda's vendors.
 It is obvious that valve was not sealing based on the carbon on the 45 cut on the seat. You need a VJ after guide replacement....get it done on a Serdi. The machinist can than perform a vacuum check for valve seal while the head is mounted in the machine. Mill that head .005 or so too.
 OEM Honda seats are soft....especially the intake. The exhaust cuts much better. I replaced the intake seats in the last head I did for my bike to fight valve recession secondary to increased spring pressure and a large cam. those seats cut mint.

[Brantley]

it looks like maybe water has been sitting and corroded the alloy away exposing the seat?is the seat fully seated,can you see where it should bottom out in its opening?

No water in the last 10 years. Been sitting in my spare room (and oiled every couple months). Can't speak for the previous 27, but I know it "ran when parked" cause I parked it!

Bead blast that chamber and the ports....you have to R&R guides. That casting anomaly won't effect anything but you can grind it a small amount to get rid of any sharp edges. I have a head sitting on my bench that has the same type of casting.....obviously caused by the die used by one of Honda's vendors.
 It is obvious that valve was not sealing based on the carbon on the 45 cut on the seat. You need a VJ after guide replacement....get it done on a Serdi. The machinist can than perform a vacuum check for valve seal while the head is mounted in the machine. Mill that head .005 or so too.
 OEM Honda seats are soft....especially the intake.

Which blast media and grit do you use?
R&R? Remove and replace? Replace and ream? I think I get ya, just makin sure... Why mill the head? (unless, of course, it's warped after I get the gasket surface cleaned up) Do I need to get the jugs milled, too?