Valve grinding

Tim Allman · Post by **Tim Allman** » Wed Apr 29, 2015 1:31 pm

I have a vague recollection of Honda warning against grinding CB77 valves but I have not been able to find any documentation of it. Has anyone here heard of this?

Thanks.

LOUD MOUSE · Post by **LOUD MOUSE** » Wed Apr 29, 2015 4:18 pm

You can grind the face of the intake but not the exhaust.
The exhaust has been treated with stelite? which hardens the face and if you grind it away the valve isn't good.
You can grind the stem of all of them. . ............lm

Tim Allman wrote:I have a vague recollection of Honda warning against grinding CB77 valves but I have not been able to find any documentation of it. Has anyone here heard of this?

Thanks.

G-Man · Post by **G-Man** » Wed Apr 29, 2015 4:33 pm

It would be interesting to know how thick the stellite application is on the valves. Triumph cam followers used to have stellite pads welded on.

http://en.wikipedia.org/wiki/Stellite

G

Tim Allman · Post by **Tim Allman** » Wed Apr 29, 2015 5:25 pm

Is lapping the exhaust valves permitted?

LOUD MOUSE · Post by **LOUD MOUSE** » Wed Apr 29, 2015 6:16 pm

Yes.
I always cut a new face in the head than lap them so I can see where the contact area is and how wide it is.
Most times the stem contact area will need to be ground to flat. ...........lm

Tim Allman wrote:Is lapping the exhaust valves permitted?

Ericvanrijn · Post by **Ericvanrijn** » Sat Aug 22, 2015 3:47 am

Hi Loud Mouse,
Let me ask you a stupid question, what is the difference between lapping and grinding?
Thanks in advance for you answer.

LOUD MOUSE · Post by **LOUD MOUSE** » Sat Aug 22, 2015 7:09 am

I'll do my best here.
Lapping: After cutting a new valve seat into the head and grinding the angular face of the valve I use a LAPPING COMPOUND and with a tool in the slot of the valve head I turn back and forth.
To see what the actual contact area (located on what part of the valve face and how wide is that contact area) I apply red or blue metal dye which is removed at the head and valve face as I turn the valve.
These engines usually have a intake valve which has a worn contact area and worn stem. (Sort of a pocket at the adjuster end)
The exhaust valve is heat treated at the contact area and should not be ground but the stem can be resurfaced.
I'm aware that those who don't have a valve machine to reface the face and stem just use the lapping compound and twist the valve back and forth hoping for something good to happen.
Been there/done that with lawn mower engines.
Years back I sent heads to a machine shop but I bought a SIOUX brand valve machine and do head work here now. .....................................lm

Ericvanrijn wrote:Hi Loud Mouse,
Let me ask you a stupid question, what is the difference between lapping and grinding?
Thanks in advance for you answer.

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